= use your "Back" button to return to ACIS
PDF documents require Adobe Acrobat Reader

Crop Advisory -May 29, 2005 Figure 1 Diagram showing Heat Unit accumulation from planting date in relation to cotton growth stage Heat Units a) Yuma valley: Heat unit (HU) accumulated since Jan 1 = 1533, last year for the same period 1738. HU accumulated since January are running 7 days behind normal. Last week HU were running 8 days behind normal b) Roll Heat unit (HU) accumulated since Jan 1 = 1520, last year for the same period= 1723. HU accumulated since January are running 2 days behind normal. Last week HU were running 3 day behind normal Estimated water use last week Planting Date 2/1 2/15 3/1 3/15 4/1 Location --Water use, inches-- Yuma 1.28 1.17 1.05 0.84 0.64 Roll 1.35 1.25 1.12 0.92 0.70 Figure 2 Soil temperature and soil moisture at 3 inch soil depth of cotton field in Somerton AZ, May 18 to May 24, 2005. Soil temperatures show high variation between day and night, with the highest temperature recorded in the afternoon and the lowest were recorded at night. Agronomy Cotton development is progressing toward its most active stage. Early planting reached pin-head square stage. In general, cotton crop is still growing behind schedule. At this stage, under the current weather conditions, the management of cotton fields will impact the final results. Therefore, field activities should focus on plant nutrition, irrigation management, pest control, and the balance between vegetative growth and fruit set by observing cotton height, number of nodes and height/node ratio. For additional information visit Arizona web site http://ag.arizona.edu/crops or call Cooperative Extension 928 726 3904 1) Plant Nutrition The assumption that vegetable crops leave sufficient residual nutrient to sustain cotton growth during the early stage or even the entire season may or may not be true. If you planted cotton after produce, it is recommended to test soil and /or plant nitrogen level and make management decisions accordingly. The application of nitrogen (side dressed or water run) should be decided based on petiole tissue testing. The accuracy of field nitrogen value depends very much on the quality of sampling strategies and sample handling. Most soil and plant laboratories are equipped with modern instrumentation capable of running a large number of samples with minimum error margin. Therefore, the true value of your field sample depends on the quality of sampling and sample handling. Inspect your cotton field uniformity and design sampling strategies. Before entering the field we need to make a sketch that divides the field into uniform and practical size that could be managed when making fertilizer adjustment. Samples from each zone can be collected as cluster, Zigzag, or random sampling. 1) if the cotton field is uniform then randomly collect several petiole samples, thoroughly mixed to form a composite sample. This composite sample should be oven dried at 150oF for 24 hours. Fresh petiole could be sent immediately to laboratory for analysis if packaged in a disposable ice chest. In any case sample should not be left in the office or truck for several days. 2) If the cotton field is divided into sections with different levels of nitrogen levels and each section is big enough to be managed separately with nitrogen adjustment then samples should be collected from each section as described in case of uniform field. How many samples per field are needed? Fewer samples may under or overestimate the real nutrient value of soil or plant level of the cotton field. A larger number of samples may cost you unnecessary charge. Based on petiole nitrate nitrogen (NO3-N) guidelines developed for Arizona upland cotton (Silvertooth), plant tissue between 15000 to 20000 PPM is considered adequate at this stage. A rapid and inexpensive method of determining nitrate status in cotton plant is often used based on Sap nitrate (NO3) or Nitrate Nitrogen (NO3-N). Sap nitrate nitrogen can be determined using a specific nitrate electrode developed by Horiba (Cardy meter). Retail price is less than $400 for one time purchase. Sensors are replaced periodically based on the use. Sap nitrate nitrogen can also be determined on the field, at the office or at home with a fraction of the cost charged by commercial laboratories.The method is quick, easy and relatively accurate. Notice that Sap nitrogen is lower than dry petiole samples. Calibration is therefore necessary. It could be determined using the equation: Y=10.21*x-1007 Y= dry petiole NO3, X= sap nitrate This method is widely used in vegetable industry and cotton production. If you have any questions about purchasing, calibrating and interpreting results using the SAP nitrate determination method, please contact your extension agent. 2) Insect control. Cotton field planted next to current cucurbit fields are more exposed to whitefly infestation. Scouting these fields allows early detection and treatment decisions to avoid any damage. For more information on pest evaluation visit web site http://ag.arizona.edu/crops, or call Mohammed Zerkoune at 726 3904, Zerkoune@ag.arizona.edu. For more information contact: Mohammed Zerkoune, zerkoune@ag.arizona.edu Extension Agent, Agriculture (Yuma County) University of Arizona, Tucson, Arizona. Disclaimers Previous Advisories Return to AZMET
Yuma County: Field Crops | Farm Notes | Alfalfa Reports | Vegetables For more Arizona Production Ag Information: Home | Cotton | Veggies| Other Crops | Crop x Crop Insects | Diseases| Weeds | Pesticides | News | Weather | Research | Contacts | General Info. document located at: http://ag.arizona.edu/crops/counties/yuma/cotton/ctnadvisoryyc.html Copyright © 2001 University of Arizona, College of Agriculture and Life Sciences webmaster: jsjones@ag.arizona.edu

Crop Advisory - May 17, 2005

Figure 1 Diagram showing Heat Unit accumulation from planting date in relation to cotton growth stage

Heat Units

a) Yuma valley:

Heat unit (HU) accumulated since Jan 1 = 1216, last year for the same period 1449. HUs accumulated since January are running 8 days behind normal.

b) Roll

Heat unit (HU) accumulated since Jan 1 = 1194, last year for the same period= 1457. HUs accumulated since January are running 4 days behind normal.

Estimated water use last week

Planting Date

2/1 2/15 3/1 3/15 4/1

Water use, inches

Yuma 0.77 0.68 0.57 0.39 0.38

Roll 0.77 0.69 0.58 0.41 0.39

Agronomy Cotton development is progressing toward its most active stage. Normal early planting should show white blooms. Cotton is still growing behind schedule. At this stage, under the current weather conditions, the management of cotton fields will impact the final results. Therefore, field activities should focus on plant nutrition, irrigation management, pest control, and the balance between vegetative growth and fruit set by observing cotton height, number of nodes and height/node ratio.

Figure 2 Sudan grass field previously planted to broccoli and irrigated every other row with water run fertilizer. As result, non uniform nitrogen level is shown on the sudan grass crop.

1) Plant Nutrition

The assumption that produce leaves behind sufficient residual nutrient to sustain field crop growth during the early stage or even the entire season may or may not be true. Figure 2 above shows the effect of uneven application (every other row) of water run nitrogen during produce production on sudan grass that followed the produce. If you planted cotton after produce, it is recommended to test soil plant nitrogen level and make management decisions accordingly.

The application of nitrogen (side dressed or water run) should be decided based on soil or plant tissue testing. Several soil or plant samples should be randomly collected and thoroughly mixed to form a composite sample. This composite soil sample should be air dried immediately before it is sent to laboratory. The composite plant sample should be oven dried at 150 F for 24 hours. Wet soil sample or fresh plant could be sent immediately to laboratory for analysis if packaged in a disposable ice chest. In any case sample should not be left in the office or truck for several days.

How many samples per field are needed? Fewer samples may under or overestimate the real nutrient value of soil or plant level of the cotton field. A larger number of samples may cost you unnecessary charge. Currently most of the laboratories are using well performing instruments to run nutrient analysis within reasonable accuracy. Error associated with sample collection and sample processing is far greater than the error associated with laboratory analysis.

Before entering the field we need to make a sketch that divides the field into uniform and practical size that could be managed when making fertilizer adjustment. Samples from each zone can be collected as cluster, Zigzag, or random sampling.

Based on petiole nitrate nitrogen (NO3-N) guidelines developed for Arizona upland cotton (Silvertooth), plant tissue between 15000 to 20000 PPM is considered adequate at this stage.

Sap nitrate nitrogen can also be determined on the field, at the office or at home with a fraction of the cost charged by commercial laboratories. The method is quick, easy and relatively accurate. Notice that Sap nitrogen is lower than dry petiole samples. Calibration is therefore necessary. It could be determined using the equation: Y=10.21*x-1007

Y= dry petiole NO3, X= sap nitrate

Sap nitrate nitrogen can be determined using a specific nitrate electrode developed by Horiba (Cardy meter). Retail price is less than $400 for one time purchase. Sensors are replaced periodically based on the use. If you have any question about the SAP nitrate determination, please contact your extension agent.

2) Insect control.

Cotton field planted next to current cucurbit fields are more exposed to whitefly infestation. Scouting these fields allows early detection and treatment decisions to avoid any damage. For more information on pest evaluation visit web site http://ag.arizona.edu/crops, or call Mohammed Zerkoune at 726 3904, Zerkoune@ag.arizona.edu.

Yuma County Crop Advisory Archives

May 9, 2005

Cotton planting was delayed this year as compared to last year due to unseasonable weather during the normal cotton planting window (mid February- March). Overall, cotton development appears to be slow as temperatures recorded during the month of April and the first week of May, were relatively low. Should growers need to replant some of their cotton fields due to inadequate stand, the cotton growth would be further delayed. Fortunately, this year there was no need for replanting cotton field.

Figure 1 Diagram showing Heat Unit accumulation from planting date in relation to cotton growth stage

Yuma

Heat Unit accumulated since January 1= 1110 in Yuma and last accumulated heat units were 1321. Since January heat units are running 7 days behind

Roll

Heat Unit accumulated since January 1= 1083 in Yuma and last accumulated heat units were 1319. Since January heat units are running 3 days behind.

Agronomic update

The number of individual plants per acre (plant population) is one of the most important components that determine final yield of any crop. Cotton lint yield (Y) is determined by the product of the number of plants (P) per acres* number of cotton bolls (B) per plant * weight of lint (W) from each boll will determine cotton yield. Y=B*N*W.

To estimate plant population count the number of plant from1/1000th of acre (ie 43560 square feet /1000=43.56 square feet). If cotton is planted on 40 inches row spacing (3.33 feet) or 42 inches (3.5 feet), then divide 43.56 by 3.33 and 3.5 to obtain the row length (13.1 and 12.4 feet) from which you count the number of plants. Multiply the number of plants counted from the 1/1000th acre by1000 to get plant population per acre.

Soil temperature and soil moisture

Soil temperatures recorded from April 24 to May 9, 2005 showed variation from day to day and within each day. Until the end of April soil temperatures were as low as 60 F in the morning and lower than 90 in the afternoon. Low temperatures slowed down cotton growth rate.

Soil moisture (kPa) indicated that soil at 3-inch deep decreased from (-18 kPa on April 28 near 2 PM to -33 kPa on May 9 at 2 PM contained enough water during last week of April, but during the first week of May soil moisture decreased to near -33 kPa (Figure 2).

Estimate water use

Planting date

Location 2/1 2/15 3/1 3/15 4/1

Water use, in.

Yuma .67 .57 .45 .39 .39

Roll .61 .53 .42 .38 .38

Figure 2Temperature and soil moisture recorded at 3-inch soil depth from cotton field planted on March 16, 2005.

IPM

Low temperatures and small slow cotton growth kept insect pressure low at this time. It is still early to notice insect infestation in the cotton fields. However, field scouting including using insect traps should have been started. Cantaloupe crop acreage has slightly increased in Yuma County. Cantaloupe crops are often planted on the fields adjacent to cotton fields. It is anticipated that during the coming weeks cantaloupe harvest begins insects will migrate from cantaloupe to cotton fields.

Yuma County Cotton Advisory

 

No crop advisory exists for April 25 or May 2

Yuma County Cotton Advisory

Cotton Advisory - April 18, 2005 Most cotton planting has now ended; nearly 100% of cotton has been planted in Yuma Valley and West of Yuma. Very few fields may be planted to cotton in the Eastern part of Yuma County this week. In spite of late planting, cotton crop development, in general, is not far behind the schedule this year compared to the previous year. Figure 1 shows a cotton field that was among the first cotton fields planted in Yuma this year. However, the majority of cotton crops are still at the younger stage, some of the cotton crops are just coming out the ground. At this point cotton stand is very good and hopefully no grower has the need to replant.

Figure 1. Cotton field among the earliest planted this year in Yuma, 2005

The temperature data this week and last week are 2 to 4 degrees below normal in Yuma, and 4 to 6 degrees below normal in Roll. The heat units accumulated are running 5 days behind in Yuma and about normal in Roll. The AZmet weather data is enclosed. Data on the web can be found at http://ag.arizona.edu/azmet/cotton.htm, click on Yuma or Roll buttons to find more details about each location.

Soil temperatures recorded at 3 inch soil depth from the cotton field (at one cotton variety trial site) is shown in Figure 2. Temperature differences (dotted lines) between days and nights are still appreciable. The highest temperatures were observed on April 13 at 2 PM where the lowest were observed on April 15, 2005. These soil temperatures changes are consistent with air temperatures recorded during the same period.

Figure 2. Temperature (left y axis and soil moisture (kpaskal) at 3 inch soil depth recorded every two hours from Somerton cotton field, April 11-18, 2005

Soil Test

It is a common practice that vegetable crops with substantial residual nutrients precede cotton crops. It is therefore assumed that soil cropped from vegetables would have enough residual nutrients to sustain growth during the early cotton growth. Although, this assumption is true for most situations in Yuma County, there are cases where soil may not have enough residual to respond the cotton nutrient need. Therefore, it is always advisable to test soil prior to cotton planting and make sure that soil is adequately supplied with nutrients needed for early cotton growth.

Table 1 illustrates the difference in soil test between two fields which were both cropped to lettuce. At each location, three composite samples made of 10 sub-samples were randomly collected from the field currently planted to cotton. Laboratory results showed low nitrate and high phosphorus from location 1. At this location, soil nitrate nitrogen appears to be low; additional nitrogen may be needed as soon as possible. In contrary, location 2 had enough nitrogen and phosphorus.

The other difference between these two soils was the level of available soil zinc, an important element needed at a small quantity for normal growth. High soil phosphorus may have enhanced zinc adsorption in the soil to hydroxides and oxides of iron. This is probably why soil high in phosphorus is low in zinc. In the plant, zinc deficiency is often related to high phosphorus content. In such a situation of high P content, a supplement of Zn is needed. Since Zinc and other micro elements are rarely tested in plant tissues during the growing season, soil test prior cotton planting may the best method of predicting your fertilizer programs.

April 11, 2005

Cotton Advisory Cotton planting in Yuma was delayed compared to the previous year. Rainfall recorded during the month of January and February delayed the harvest of vegetable fields reserved for cotton crop planting. Some growers plant cotton on dry fields during early February then irrigate when soil temperature is adequate for cotton seed germination. This year few acres have been planted prior to March, because of high rainfall that kept soil wet thus inaccessible to farm implements needed to prepare fields after vegetable harvest. The Figure illustrates the rain distribution from January 1, 2004 to April 10, 2004 and 2005 at Yuma and Roll AZMET weather stations. The Figure 1 also shows that at Roll Station total rainfall recorded from January to April 10, 2005 was more than double the rainfall recorded in 2004 for the same period. It was 70% of Yuma total annual rainfall (3.7 inches).

Figure 1 Precipitation recorded at Roll and in Yuma AZMET weather stations from January 1 and April 10, 2004 and 2005.

Currently it is estimated that 95% of cotton has been planted in Yuma County. The total acreage planted in Yuma County has increased by about 4 to 5% from last year. In addition to late planting, the cotton growth rate is slowed down by the low temperatures recorded after planting at both Roll and Yuma Stations as shown in Figure 2. Maximum and minimum temperatures recorded during March and the first 10 days of April this year were consistently lower than those recorded during the year 2004 for the same period. Consequently, cotton is growing slowly. It is anticipated that this year cotton crop is growing within a shorter growing season since cotton growers start harvesting during early August to accommodate vegetable planting. Under these circumstances fertilizer and irrigation programs would play a key role in balancing between vegetative growth and reproductive cycle.

On the field, soil temperatures recorded at 3 inch soil depth shown in Figure 3 indicate a wave movement of temperature between night and daytime with the highest recorded between 2:00 to 4:00 PM (77 to 82F), and the lowest recorded between 5:00 and 8:00 AM (51 to 53 F).

Figure 2 Minimum and Maximum temperatures recorded at Roll and Yuma AZMET Weather Stations from Jan 1-April 10, 2004 and 2005.

Figure 3 Soil temperature recoded from cotton field at 3-inch soil depth from April 5-11, 2005) Somerton AZ.

April 5, 2005

It is not unusual in Yuma to start planting cotton in mid February and ending late April. Cotton is planted on dry soil then irrigated when temperatures are more likely to reach optimum for germination. This year however, the cold and rainy weather delayed vegetable harvest and cotton planting. Growers are still planting the last cotton fields. Temperatures are high enough to favor rapid cotton germination. Figure 1 shows temperatures recorded at 3 inch soil depth. Temperatures varied from 50F early in the morning to near 70F in the afternoon. Soil moisture shown on right Y axis indicates that the water pressure was low (high negative number) before irrigation then increased rapidly following the irrigation before it started to decrease as water drained from the soil profile. The irrigation helped the initiation of the rapid cotton seed germination.

Figure 1 shows temperatures (left axis) and soil moisture ( right axis) recorded at 3 inch soil depth every two hours from March 31 to April 5, 2005 on cotton field planted on March 29, 2005, irrigated on April 1, 2005.

Cotton planted early is currently performing well. Cotton field shown below (Figure 2) was planted in mid March is just coming out of the ground. The overall cotton stand appears to be good. A good cotton stand is achieved when cotton health and nutrition are carefully monitored. During the early cotton stage, small plants require a small amount of nitrogen, often available in soil as N residual from previous vegetable crops. As cotton plant continues to develop rapidly toward the beginning of "pin square" stage, the level of plant nitrogen should be monitored to prevent any prolonged deficiency. Note that the level of nitrogen in plants is high at early stage and decreases progressively with age (Figure 3).

 

Figure 2. Cotton planted in mid March 2005 on wet field germinated with good and uniform stand

The best way to know about the status of nitrogen level in cotton plants is to use tissue testing. Tissue testing should be conducted periodically to check nitrogen level in cotton plants. Figure 3 shows that nitrogen level changes as plants develop during the season. The N concentration at the beginning is high, then decreases toward the end of the season. Make sure to read nitrogen status on the same scale of reference.

Some laboratories report results as Nitrate (NO3) and others report as Nitrate Nitrogen, NO3-N. The plant nitrogen level can be determined in a commercial laboratory. This method although the most reliable, it costs and requires travel time for sample to reach commercial laboratory. Therefore, the results take time before they are returned from a laboratory.

There are several alternative reliable methods that can save you money and time. These alternative methods are inexpensive and reasonably accurate. If you are interested in using any method currently available, the calibration, and interpretation please contact Mohammed Zerkoune at 928 726 3904.

Fig 3 Nitrate status in cotton From T. Doerge, R. Roth, and B Gardener, 1991

It is more difficult to notice nitrogen deficiency in cotton than in wheat based on visual observation. How do you know cotton is nitrogen deficient? The old leaves at the bottom of the plant do not turn as yellow as you see them on wheat. In addition, you do not really wait until deficiency symptoms appear on cotton leaves (yellow) before making nitrogen adjustment because at that point the damage is done and may be irreversible. The Figure 3 shows Nitrate Nitrogen based on dry tissue material. Sap Nitrate Nitrogen level is considerably lower since it is diluted.

It is important to realize that major sources of soil or tissue testing errors are due to inappropriate sampling and sample handling. Most laboratories conducting routine soil and plant tissue testing are equipped with modern and accurate instrumentation capable of performing accurate analytical determination. In order to minimize errors in your sampling program, it is very important to pay attention to the sampling method and sample handling. If you are not sure how to collect and handle samples, or if you want to conduct your own tissue testing, using common instruments available on the market, you can save money. Please contact Mohammed Zerkoune at Yuma Cooperative Extension.

March 28, 2005 Vegetable harvest was delayed this year due to the uncharacteristic weather season. However, vegetable harvest is getting close to the end with few lettuce fields left to harvest, freeing land for last cotton planting. Current and expected soil temperatures for the coming days in Yuma area are favorable for cotton planting and rapid seed germination. Soil temperature and moisture collected near seed planting depth during the week of March 19 through March 28 in variety trial field planted on March 16, 2005 in Wellton AZ.

Temperatures were 43F during the first few days following planting, but increased rapidly toward the 28th of March. Noticeable temperature variation between days and nights with the highest temperatures recorded during the afternoon and the lowest were recorded after midnight. Soil moisture recorded in Kilopascal (Kpa) was recorded at the same time as temperatures. Although variation between nights and days were significant, seed germination was very satisfactory. The temperatures during this week were favorable for finishing cotton planting. Cotton follows lettuce and other vegetables in the crop rotation systems. Research data indicate that nitrogen and phosphorus residuals from vegetable crop are enough to sustain cotton growth during early stage. At the early stage, cotton requires a small amount of nutrients to achieve normal growth. Residual nitrogen from vegetable fields often meets cotton nutrient demand during the early stage or even the entire cotton growing season. A typical residual nutrient of field, with medium soil texture, planted to lettuce is represented with the mean of 3 composites of 10 samples randomly collected throughout the field illustrate the soil nutrient sufficiency level for early growth when cotton follows lettuce or other vegetables in crop rotation systems. However, fertilizer adjustment should rely on soil test. It is important to keep in mind that when crop nutrient deficiency symptoms appear, the damage is already done. If the damage is severe, the correction is often irreversible.

Nitrogen is often side dressed, the amount of nitrogen fertilizer needed to apply should be determined based on soil test. Later in the season nitrogen level in the plant is evaluated by petiole samples. The number of soil and plant tissue samples needed depends on field size and uniformity. In the coming crop advisory I will say more about plant tissue analysis.

Watermelon crop transplanted is progressing well. In the early watermelon planting first flowers are appearing. Cantaloupe planted on "Yuma bed system" is growing well and on time. It is too early to notice any sign of nutrient deficiency, disease or insect damage. Mohammed Zerkoune, Ph.D. Extension Agent, ANR Zerkoune@ag.arizona.edu

August 25, 2003

Weather advisory

Yuma Heat unit (HUs) accumulation since January first in Yuma valley reached 3963. Last year HUs for the same period were3974 and 4003 for normal. HUs are running 1 day late behind normal. HUs in Yuma valley since February 15, 2003 first planting reached 3695 Roll HUs accumulation since January for Roll area reached 3847. Last year HUs totaled 3781 for the same period. HUs are running about two days ahead of normal in roll area.. HUs since first planting totaled 3590.

Crop advisory

Cotton harvest began last week in Yuma. Most of cotton crops have reached a termination stage. For the remaining of the cotton season focus should be on preparing for cotton harvest. Whitefly pressure has been higher this year than it was last year. Therefore, whitefly control remains a critical point to observe even after cotton fields are defoliated. For more information on whitefly scouting and treatments visit http://ag.arizona.edu/crops, or contact Yuma Cooperative Extension to obtain a hard copy.

Four upland variety trials have been conducted this year at Wellton and Yuma locations. Should anyone be interested visiting any field or need plot plan would contact Mohammed Zerkoune at 726 3904 or zerkoune@ag.arizona.edu.

Preliminary results of the early planting variety trial indicated that seed and fiber yield obtained from most varieties was high. DP 448B had the highest yield and DP 555BR had the lowest yield. Complete yield data will be sent out after ginning and the fiber quality is determined in the laboratory.

EVENTS ?August 26, 2003, 9:00 at AWC Vocation Center in Parker AZ Hands on Computer Application Workshop for Crops if interested to attend, please call Eric Norton, 928 6699843 by 8-25-03 ?Yuma County Cotton Field day is scheduled for the second week of September at Wellton AZ to discuss the performance of newly developed and existing cotton varieties, planting dates and twin line management systems. ?December 3, 2004: Desert Crop workshop location TBA Web based Pinmap has been open since July 1, 2003. Visit University of Arizona web site. http://minu.arec.arizona.edu/pinmap If you need password or training how to use pinmap, please contact Mohammed Zerkoune at zerkoune@ag.arizona.edu For any question, comment regarding this crop advisory, please contact Mohammed Zerkoune Zerkoune@ag.arizona.edu, Phone 928 726 3904, mobile 928 580 0222

August 18, 2003

Weather advisory

Yuma Heat unit (HUs) accumulation since January first in Yuma valley reached 3756. Last year HUs for the same period were 3781 and 3802 for the normal. HUs are running 2 days late behind normal. HUs in Yuma valley since February 15, 2003 first planting reached 3281 Roll HUs accumulation since January for Roll area reached 3646. Last year HUs totaled 3605 for the same period. HUs are running about two days ahead of normal in roll area. HUs since first planting totaled 2990.

Crop advisory

Cotton harvest began last week in Yuma. Most of cotton crops have reached a termination stage. For the remaining of the cotton season focus should be on preparing for cotton harvest. Whitefly pressure has been higher this year than it was last year therefore whitefly control remains a critical point to observe even after cotton fields are defoliated. For more information on whitefly scouting and treatments visit http://ag.arizona.edu/crops, or contact Yuma Cooperative Extension to obtain a hard copy.

Four upland variety trials have been conducted this year at Wellton and Yuma locations. Should anyone be interested visiting any field or need plot plan would contact Mohammed Zerkoune at 726 3904 or zerkoune@ag.arizona.edu. Preliminary results of the early planting variety trial indicated that seed and fiber yield obtained from most varieties was high. (See table below). DP 448B had the highest yield and DP 555BR had the lowest yield. The table below summarizes the results. After ginning and fiber quality is determined the final results will be made available.

 

DP448B ST5599BR DP565 ST457 DP 449BR ST 4691B AGriPro7126 DP 555BR Seed +lint (lb/A 7912A 7829A 7660A 7112B 7053B 7053B 6917B 6553C

Varieties followed by the same letter are not significantly different at 5% alpha level

Water use

Area Planting date 2-01 2-15 3-01 3-15 4-01

Yuma, in 1.44 1.52 1.63 1.79 1.98

Roll, in 1.49 1.57 1.69 1.84 1.88

EVENTS August 26, 2003, 9:00 at AWC Vocation Center in Parker AZ. Computer Application Workshop for Crops if interested in attending, please call Eric Norton, 928-669-9843

Yuma County Cotton Field day is scheduled for the second week of September at Wellton AZ to discuss the performance of newly developed and existing cotton varieties, planting dates and twin line management systems.

December 3, 2004: Desert Crop workshop location TBA Web based Pinmap has been open since July 1st 2003. Visit University of Arizona web site http://minu.arec.arizona.edu/pinmap If you need password or training how to use pinmap, please contact Mohammed Zerkoune at zerkoune@ag.arizona.edu For any question, comment regarding this crop advisory, please contact Mohammed Zerkoune Zerkoune@ag.arizona.edu, Phone 928 726 3904, mobile 928 580 0222

August 11, 2003

Weather advisory

Yuma Heat unit (HUs) accumulation since January 1st in Yuma Valley reached 3549. Last year HUs for the same period were 3576 and 3600 for the normal. HUs are running 2 days late behind normal. HUs in Yuma Valley since the February 15, 2003; first planting reached 3281 Roll HUs accumulation since January for Roll area reached 3443. Last year's HUs totaled 3409 for the same period. HUs are running about one day ahead of normal in Roll area. HUs since first planting totaled 2990.

Crop advisory Cotton harvest is underway. All cotton fields have reached cutout stage. Most of the cotton crops have reached a termination stage. Open bolls have been observed on early and mid season cotton planting. Focus should be on preparing for cotton harvest. Some of the early planted fields have been already defoliated and the harvest season is set to begin next week. Irrigation management and whitefly remain critical points to observe even after cotton fields are defoliated, since whitefly pressure is higher this year than it was last year. For more information on whitefly scouting and treatments visit http://ag.arizona.edu/crops, or contact Yuma Cooperative Extension to obtain a hard copy.

Four upland variety trials have been conducted this year at Wellton and Yuma locations. Should anyone be interested visiting any field or need plot plan, contact Mohammed Zerkoune at 726-3904 or zerkoune@ag.arizona.edu. Field Day is scheduled for the second week of September, 2003. More details will follow.

Water use

Area

Planting date 2-01 2-15 3-01 3-15 4-01

Yuma, in 2.12 2.21 2.35 2.46 2.46

Roll, in 2.15 2.25 2.34 2.34 2.34

EVENTS

Pre-season Workshop is scheduled for August 19, 2003 at Yuma Cooperative Extension office. Nine research scientists are expected to make presentations on various subjects related to vegetable production including: insect management, update on fusarium, sclerotinia on lettuce and melon, weed control, irrigation and soil fertility management. 3.5 Continuing Education hours granted from Arizona and 3.5 granted from California and 4.0 applied for from CCA.

Yuma County Cotton Field day is scheduled for the second week of September in Wellton, AZ ,to discuss the performance of newly developed and existing cotton varieties, planting dates, and twin line management systems.

December 3, 2004: Desert Crop workshop. Location TBA Web based Pinmap has been open since July 1st 2003. Visit University of Arizona web site. http://minu.arec.arizona.edu/pinmap If you need password or training on how to use the pinmap, please contact Mohammed Zerkoune at zerkoune@ag.arizona.edu For any questions or comments regarding this crop advisory, please contact Mohammed Zerkoune Zerkoune@ag.arizona.edu, Phone 928 726 3904, mobile 928 580 0222

Crop Advisory, August 4, 2003

Weather advisory

Yuma Heat unit (HUs) accumulation since January 1st in Yuma valley reached 3346. Last year HUs for the same period were 3380 and 3394 for the normal. HUs are running 2 days late behind normal. HUs in Yuma valley since February 15, 2003 first planting reached 3078. Roll HUs accumulation since January for Roll area reached 3247. Last year HUs totaled 3219 for the same period. HUs are running about one day ahead of normal in Roll area. HUs since first planting 2990.

At this point in time all cotton fields have reached cutout stage. Early planting cotton has reached a termination stage. Open bolls are observed on earliest and mid season cotton planting. Focus should be on preparing for cotton harvest. Irrigation management and whitefly remain critical points to observe even after cotton field are defoliated. For more information on whitefly scouting and treatments visit http://ag.arizona.edu/crops.

Four upland variety trials have been conducted this year at Wellton and Yuma locations. Anyone interested in visiting any field or need plot plan can contact Mohammed Zerkoune at 726 3904 or zerkoune@ag.arizona.edu. Field day is scheduled for the second week of September 2003; more details will follow.

Water use Area Planting

date 2-01 2-15 3-01 3-15 4-01

Yuma, in 2.03 2.06 2.06 2.06 2.06

Roll, in 1.97 1.97 1.97 1.97 1.97

Figure 1 Maximum, minimum and average daily temperatures

From July 1 to August 4, 2003 in Yuma Valley and Roll area.

Events

August 19, 2003: Pre-season Vegetable workshop, Yuma County Cooperative Extension. 3.5 CEUs GRANTED for AZ, 4 CEUS were applied for from CCA and CA. Subjects covered include: insect management, update on fusarium, sclerotinia on lettuce and melon, weed control, irrigation and soil fertility management.

December 3, 2004: Desert Crop workshop location TBA Web based Pinmap has been open since July 1, 2003. Visit University of Arizona web site at http://minu.arec.arizona.edu/pinmap If you need password or training how to use pinmap, please contact Mohammed Zerkoune at zerkoune@ag.arizona.edu For any question, comment regarding this crop advisory, please contact Mohammed Zerkoune Zerkoune@ag.arizona.edu, Phone 928 726 3904, mobile 928 580 0222

 

Crop Advisory, July 27, 2003

Weather advisory

Yuma

Heat unit (HUs) accumulation since January 1st in Yuma valley reached 3142. Last year HUs for the same period were 3180 and 3192 for the normal. HUs are running 2 days late behind normal. HUs in Yuma Valley since February 15, 2003, first planting reached 2874

Roll

HUs accumulation since January for Roll area reached 3050. Last year HUs totaled 3029 for the same period. HUs are running about one day ahead of normal in roll area. HUs since first planting 2793.

Warm temperatures combined with high humidity are conducive to generate heat stress in both Yuma and Roll areas. Stress level 2 was observed during the most of last week, indicating damages on young squares and heavy fruit shed that will continue for sometime during next week. Warm and humid conditions continue during this monsoon weather with high pressure and intense thunderstorm activity in both areas (AZMET)

Crop advisory

At this point in time all cotton fields have reached pink bloom stage. Fertilizer and growth regulator is past due. Mid-season planting has reached cutout stage, open bolls are observed on earliest planting. Focus should be on retaining fruit sets and preparing for cotton harvest. Irrigation management and whitefly remain critical points to observe. For more information on whitefly scouting and treatments visit http://ag.arizona.edu/crops.

Four upland variety trials have been conducted this year at Wellton and Yuma locations. Should anyone be interested in visiting any field or need plot plan, contact Mohammed Zerkoune at 726 3904 or zerkoune@ag.arizona.edu

Insect pressure is expected to increase as temperatures rise in coming days. Scouting and sampling should continue in order to determine whether or not insecticide application is justified. Sampling for whiteflies and other insect pressure is necessary in order to determine the need and the timing of insecticide application

Water use

Planting date 2-01 2-15 3-01 3-15 4-01

Yuma, in 2.45 2.45 2.45 2.45 2.45

Roll, in 2.33 2.33 2.33 2.33 2.33

Events August 19, 2003: Pre-season Vegetable workshop, Yuma County Cooperative Extension. 3.5 cr for AZ, 4.5 cr for CA and CCA were applied for. Subjects covered include insect management, update on fusarium, sclerotinia on lettuce and melon, weed control, irrigation, and soil fertility management.

December 3, 2004: Desert Crop workshop location TBA

Web based Pinmap has been open since July 1, 2003. Visit University of Arizona web site http://minu.arec.arizona.edu/pinmap If you need password or training how to use pinmap, please contact Mohammed Zerkoune at zerkoune@ag.arizona.edu For any question, comment regarding this crop advisory, please contact Mohammed Zerkoune Zerkoune@ag.arizona.edu Phone 928 726 3904 Mobile 928 580 0222

Crop Advisory, July 14, 2003

Cotton development is proceeding at rapid pace with temperatures on the rise and dry conditions. Planting date of cotton extended from mid February to the end of April, thus cotton stage varies with planting date. Most cotton fields planted early developed and maintained good fruit sets and boll retention and yield potential. On those fields cotton crop is mature enough that any eventual insect damage is expected to be minimum.

Later planting also is progressing as well as expected but good irrigation management and insect scouting should be rigorous in order to increase fruit retention and ovoid insect damage. In all cases insect scouting should continue in order to assess the need for control even after cutout when the whitefly population should decline. Last week Cross-Commodity Guidelines for Neonicotinoid Insecticides in Arizona were sent out to help improve the efficacy of these insecticides applied on different crops. The information is available on the University of Arizona http://ag.arizona.edu/pubs/insects/az1319.pdf or call Yuma County Cooperative Extension.

Water Use Location Planting date

2-01 2-15 3-01 3-15 4-01

-------------inches--------------------------

Yuma 2.67 2.67 2.67 2.67 2.55

Roll 2.63 2.63 2.63 2.63 2.38

Watermelon harvest is progressing toward the end of the season. Some heat stress was observed on watermelon crops due to recent elevated temperatures. Preparation for new vegetable season is underway

Event Pre-season vegetable workshop is rescheduled for August 19- 2003. Main topics include research update on irrigation management, soil and plant nutrient management, soil amendments, integrated pest management, vegetable breeding for pest resistance

Crop Advisory, July 6, 2003

Yuma Heat unit (HUs) accumulation since January 1st in Yuma valley reached 2522. Last year HUs for the same period were 2575 and 2602 for the normal. HUs are running 3 days late behind normal. HUs in Yuma valley since February 15, 2003 first planting reached 2254. Roll HUs accumulation since January for Roll area reached 2248. Last year HUs totaled 2436 for the same period. HUs are running about normal in roll area.

Crop advisory

Most of the cotton crop should have received one or two applications of growth regulator. Few observations collected on cotton fields across the county indicated that cotton planted on March 27 this year is about 22 inches high, and height/node ration is near 1.4. Cotton planted on February 10, 2003 is 44 inches high and height/node ratio of 2.3. All the fields from which observations were collected received one or two growth regulator applications. Four upland variety trials have been conducted this year in Wellton and Yuma. Anyone interested in visiting any field or need plot plan, contact Mohammed Zerkoune.

Insect pressure is expected to increase as temperatures rise in coming days. Scouting and sampling should continue in order to determine whether or not insecticides application is justified. Sampling for whiteflies and other insect pressure is necessary in order to determine the need and the timing of insecticide application. Growers have already started treating some fields in the field. University of Arizona researchers have developed procedures for sampling nymphs to help obtain the most benefit from the application of insect growth regulators. More information on sampling and timing of application can be found at http://cals.arizona.edu/pubs/insects/az1319.pdf "Cross Commodity Guidelines for Neonicotinoid Insecticides in Arizona developed by University of Arizona researchers to help understand the fundamentals, sampling and treatments of whiteflies.

Water use Area

Planting date 2-01 2-15 3-01 3-15 4-01

Yuma 2.75 2.75 2.75 2.61 2.29

Roll 2.72 2.72 2.67 2.45 2.14

Events August 15, 2003: Pre-season Vegetable workshop, Yuma County Cooperative Extension December 3, : Desert Crop workshop location TBA Web based Pin map has been open since July 1, 2003. Visit University of Arizona web site. http://minu.arec.arizona.edu/pinmap If you need password or training how to use pin map, contact Mohammed Zerkoune For any question, comment regarding this crop advisory, please contact Mohammed Zerkoune Zerkoune@ag.arizona.edu Phone 928 726 3904 Mobile 928 580 0222

Current AZMET Weather Updates (PDF files):

• Roll
• Yuma Valley

 

Crop advisory June 16, 2003 Most of the cotton crop should have received one or two application of growth regulator. Observations made across the county on DP 449 BR variety indicated that cotton planted early this year is about 48 inches high, and height/node ration is near 2.0. Planting made between the last week of March and first week of April for the same variety is about 20 inches high and the height/node ration is about 1.4. All the fields from which observations were made had received one or two growth regulator application.

Insect pressure in Gila Valley is currently not of great concern, Yuma Valley is somewhat high. Growers have already started treating some fields. Sampling is necessary for timing control of whiteflies. Sampling nymphs is important to obtain the most benefit from the application of insect growth regulators. More information on sampling and timing of application can be found http://cals.arizona.edu/crops/cotton/insects/wf/ipm6.html

Heat Units accumulated (HUs) in Yuma Valley since January first 2003 are 2163. Last year HUs were 2214 for the same period. This year HUs are running 3 days behind normal of 2230.

Heat Unit accumulated (HUs) in Roll since January are 2105, last year they were 2087 for the same period. HUs are running one day ahead of normal.

Research indicated that most of the cotton nitrogen needs are met 100 days after planting. The highest daily nitrogen uptake for cotton plant occurs at pink bloom. The Nitrate-Nitrogen in petiole tissue is high when plants are young then diminishes as they grow older. Detailed information on nitrogen sufficiency level can be found at http://ag.arizona.edu/pubs/crops/az1243.pdf If you do not have access to the internet and would like to have this information please contact Mohammed Zerkoune at Yuma County Cooperative Extension, 928 726 3904

Coming events: Pre-season Vegetable Workshop: August 15, 2003 Yuma County

June 16, 2003

Events: Mid-Season Cotton Workshop; June 18, 2003, 8:00 - 1:00pm at the Yuma County Cooperative Extension Ofc.

August 15, 2003 (tenative) Pre-Season Vegetable Workshop

June 10, 2003

Early planting should have developed 12 to 13 nodes by now and the height about 30 to 35 inches. Cotton development will proceed rapidly across the county as the temperature increases. Research work in Arizona indicated that the development of one cotton-node requires 100 heat units (HU). Heat unit accumulation for selected planting dates for Yuma and Roll are as follows:

Planting date	Yuma	Roll
Feb 1	1575	1545
Feb 15	1515	1474
Mar 1	1422	1377
Mar 15	1294	1251
Apr 1	1107	1066

Heat units(HUs)accumulated in Yuma since January 1st this year, last year for the same period and normal total 1848 1877 and 1895, respectively. HUs are running two days behind normal. In the Roll area the HUs accumulated since January 1st and last year for the same period are 1802 and 1758, respectively. HUs are running two days ahead of normal.

Cotton requires a small amount of nutrient at the early stage. In general, at this stage, residual fertilizer from previous crops (vegetables) supplies adequate amount of nutrients for cotton. As cotton plant develops its nutrient requirement and water consumption increase. Water use is also affected by the evapotranspiration demand as temperatures increase. It is important to avoid any water stress since water stress will decrease fruit set retention and cause delay in crops. The estimated water use (inches of water) for Yuma and Roll areas for selected planting date are as follows:

Planting date	Yuma	Roll
Feb 1	1.8	1.8
Feb 15	1.7	1.68
Mar 1	1.55	1.52
Mar 15	1.34	1.31
Apr 1	1.04	1.01

Cotton petiole or soil samples need to be collected and analyzed in order to determine the nutrient status in plant or nutrient supply level in the soil. Nutrient balance and water supply need to be monitored attentively. Melons, alfalfa and cotton are concurrently grown in Yuma County. There is a possibility of inter-crop movement of whitefly.

Melon harvest and crop termination will increase the chances of whitefly migration to cotton fields. It is important to monitor and control the whitefly pressures on the crops. More information can be obtained at http://ag.arizona.edu/crops

Events Pre-season Cotton Workshop (PDF file) is scheduled for June 18, 2003 at Yuma County Cooperative Extension auditorium from 8 am to 1: 30 pm. Lunch will be provided and there is no charge for the registration. Cotton Workshop is sponsored by the industry.

Vegetable seed Internet Pinning map training is scheduled for the 3rd week of June, 2003 at Arizona Western College Computer Laboratory. Questions, comments please contact Mohammed Zerkoune Zerkoune@ag.arizona.edu or 928 726 3904.

June 2, 2003

Determining the Mainstem Node Number for Cotton (Publication az1207)

by Jeffrey C. Silvertooth, Extension Agronomist - Cotton

Paul W. Brown, Extension Biometerologist

To systematically monitor a young crop effectively, it is important to understand the fundamentals about counting and identifying nodes on the plant. A mainstem node is simply the point on the plant stalk where a joint with a side branch (either vegetative or fruiting branch) is formed. The basic point of reference for counting nodes on a cotton plant are the cotyledonary nodes. The cotylendonary leaves are the first two leaves to appear as the plant emerges through the soil after planting, and are actually the former halves of the seed itself. Therefore, the cotyledons form the first nodes on the mainstem of the plant and they are the only nodes which are directly opposite one another, or parallel. When counting mainstem nodes we use the cotyledon nodes as 0, then counting subsequent nodes up the mainstem toward the terminal of the plant.

For example in Figure 1, a general diagram of a young cotton plant is shown with the cotyledonary nodes at the base of the plant, the first five nodes being vegetative branches, and the first fruiting branch is shown at node 6. Usually, we include the terminal node of the plant if the first leaf attached to it (a subtending leaf) is one inch in diameter or greater (about the size of a quarter). If that were the case in the example shown in Figure 1, then we would count that plant as having a total of 8 mainstem nodes.

Non-stressed cotton plants in Arizona will produce a new mainstem node with approximately every additional 100 heat units accumulated since planting (HUAP). However, we can track mainstem node production more accurately following a simple mathematical relationship, where: Nodes = 3.8 + 0.008 (HUAP). According to this relationship, we would expect the following mainstem nodes at various stages of growth or HUAP: 9 nodes @ 700 HUAP; 13 nodes @ 1200 HUAP; 20 nodes @ 2,000 HUAP; and 24 nodes @ 2500 HUAP. So the number of nodes on the plant can serve as a good indicator of plant age. By reviewing a number of plants in a field, similar to the one diagrammed in Figure 1, we could see that generally the crop should have about 600 HUAP and that the first fruiting branch is commonly occurring at node 6, with squares continuing to form on subsequent fruiting branches.

It is important for us to also note whether the squares are being retained on the plant and not aborted. Causes of square abortion can include insect damage, dry conditions (plant desiccation), wind or sand damage, etc.. Excessive square loss early in the season can stimulate vegetative growth and create a plant that is difficult to control for quite some time. Vegetative growth tendencies will usually not affect the rate of node development, but the length of the internodes will commonly increase. This relationship offers the foundation for the development of the height:node ratio (HNR) as a measure of the level of vegetative growth or vigor of a crop.

---

May 27, 2003

Heat units( HU) accumulation in Yuma Valley since January first = 1507, 4 days behind normal of 1588. Heat uniit accumulation for Roll area =1467, running. For the same period last HUs were 1457 and 1443 for Yuma and Roll, respectively.

Water use, inches (last week)

Planting date	2/1	2/15	3/1	3/15	4/1
Yuma	1.24	1.14	1	0.79	.50
Roll	1.17	1.06	0.91	0.71	0.45

Cotton fields planted in mid-February started to have their first flowers; fields planted in late April have emerged. At low elevation, earliness is important for several reasons. Toward the end of the summer season, daily and nocturne high temperatures associated with elevated relative humidity make cotton crops difficult to form and maintain to maturity additional fruit sets. Since vegetables are predominant in farming decisions, cotton tends to be harvested early to accommodate vegetable planting. Insect pest pressures tend to be high later rather than early in the season. (J Silvertooth, ag.arizona.edu/crops/cotton.) For these reasons, it is important to establish an early cotton crop in Yuma and closely observe the cotton growth stage. Early season crop management can be found at above URL or contact Yuma County Cooperative Extension.

Two variety trials of eleven varieties each were conducted in Roll and Yuma. Anyone interested in visiting these trials should contact Mohammed Zerkoune.

Event Mid-season cotton workshop is set for June 18, 2003 at Yuma County Cooperative Extension Office.

---

May 19, 2003

Heat unit (HUs) accumulated since January 1st for Yuma = 1349 compared to 1429 last year for the same period. HUs are running about 4 days behind normal. HUs for Roll since January = 1312 compared to 1325 last year for the same period. For more information on heat accumulation go to http://ag.arizona.edu/azmet select Roll or Yuma Valley.

Water Use

Planting Date:	2/1	2/15	3/1	3/15	4/1
Yuma	.78"	.71"	.59"	.43"	.36"
Roll	.75"	.67"	.55"	.39"	.39"

Figure 1 Heat unit accumulated for two representative regions in Yuma County, adopted from AZMET.

Crop update:

Vegetables: Cantaloupe, honeydew and watermelon are the main vegetable crops growing currently in Yuma County. Low temperatures observed earlier delayed cucurbit harvest. Melon and cantaloupe crop harvest is currently underway. Crop watch should focus on scouting viral diseases and insect infestation.

Cotton: Early cotton planting (February) has reached pin head stage. After the successful stand establishment, the focus should be now on managing crop development: irrigation management, insect infestation control and crop nutrition. More information is available at http://ag.arizona.edu/crops

Three cotton variety trials are conducted in San Luis, Yuma and Wellton. If anyone is interested in evaluating these varieties contact Mohammed Zerkoune at 928-726-3904 or email zerkoune@ag.arizona.edu.

Event: Mid-season cotton workshop is scheduled for June 18, 2003 at Yuma County Cooperative Extension office from 8-1 pm. Biotechnology, economics, heat stress damage, industry update and agricultural safety.

---

May 12, 2003

Cotton growth and development is govern by the heat.

In Yuma, Heat Units (HU) accumulated since January are 1218, last year for the same period HUs were 1288 and 1299 for normal. We are running four days behind for the Yuma area. In the Roll area the HUs recorded since January total 1187 and 1190 last year for the same period. There appears to be some delay in cotton growth this year. Even early cotton plantings have no head square formation yet.

The importance of cotton earliness has gained some interest among producers who practice cotton/vegetable rotation systems. As vegetables are becoming more dominant crops in Yuma County the management decision is often made to accommodate early vegetable planting. Thus it is important to make management decision to achieve early crops with high yield potential. Some early decision to take include providing good nitrogen nutrition combined with good irrigation management and whitefly and bollworm control.

Vegetables precede cotton in crops rotation systems. They leave behind an appreciable amount of residual nutrients enough to sustain cotton growth during the early growth. Later soil or plant petiole tissue should be tested to make sure that adequate amount of nitrogen is provided. If you are testing cotton tissue the petiole NO3-N concentration should be between 15000 and 28000 part per million (pm), petiole NO3-N concentration below 15000 is considered as deficient at this stage. This concentration diminishes as cotton plant is getting older. Notice that this concentration is based on plant dry matter and Nitrate-Nitrogen. For further information, contact Zerkoune@ag.arizona.edu, or call Yuma County Cooperative Extension or visit University of Arizona Web site http://ag.arizona.edu/crops/cotton

Upcoming Events: Mid-season cotton workshop is scheduled for June 18th at 8:00 am at the Cooperative Extension Office. Within the next few weeks the agenda will be drafted and sent out.

---

May 5, 2003

Planting season is longer than harvest season for the cotton crop in Yuma County, since the planting window extends from mid-February to the first week of May while the harvest season extends from last week of August to the end of October. Both planting and harvest are dictated by the vegetable planting and harvesting program. In general cotton planting is done earlier in Yuma than Roll area. This year the first cotton planting is 8 to 12 inches high as shown in the picture below.

Most of the Yuma fields are showing some slow rate of development due to cool temperatures recorded this season. Heat unit accumulation since January is 1130, two days behind from normal at 1166. For the same period last year heat unit was 1157. For the east valley of Roll the heat unit is 1108 this year, for the same period last year heat unit was 1069. We are three days ahead of normal. For more information please check the website http://ag.arizona.edu/azmet/data/24.pdf

For days to come, the focus should be on plant nutrition, irrigation management and pest control. Cotton field planted next to current cucurbit fields are more exposed to whitefly infestation. Scouting these fields allows early detection and treatment decision when appropriate. For more information on pest evaluation visit web site: http://ag.arizona.edu/crops.

First side dress nitrogen should be starting soon. The application of nitrogen should be decided based on soil testing. Several samples should be collected and thoroughly mixed to form a composite sample. This composite sample should be air dried immediately before it's sent to laboratory. In any case wet sample, closed in the bag should not be stored in the office for several days.

---

April 28, 2003

At this time, about 95% of the cotton fields have been planted. If fields are still to be planted, special considerations should be given to selection of varieties. Short maturity types should be considered. In addition, where replanting appears to be necessary during next few days, the choice of variety becomes increasingly important as we are approaching the end of planting season.

Cotton planted in mid-February has reached five-leaf stage. Cotton planted during the first week of April is at 2-3- leaf stage. The growth rate for early planting appeared to be slow this year because of low temperatures. The cotton growth rate will increase with temperatures during the next week or two. Start to carefully observe insect pressures, nutrient balance and water demand.

Cotton is generally planted behind vegetables that leave an appreciable amount of residual fertilizer to sustain a cotton growth during the early season. Later cotton plant may need additional nitrogen. Nitrogen can be side dressed or water run. Soil and/or plant samples are essential to determine if nitrogen is needed and the amount of nitrogen to apply. Most laboratories have adequate laboratory equipment to run the soil and plant analysis with minimum error. Therefore, sampling techniques and sample handling remain the greatest source of error in estimating soil and plant nutrient level.

Most common sampling pattern consists of collect sampling in zigzag pattern. Ten to 20 soil samples should be collected and mixed to form a composite sample for every manageable field. Increase the number of samples with field heterogeneity. If sampling is made on cotton petiole then the number of petioles should be between 30 and 50 petioles in zigzag pattern.

Upcoming Events: Mid-season cotton workshop is scheduled for June 18th at 8:00 am at the Cooperative Extension Office. Within the next few weeks the agenda will be drafted and sent out.

---

April 21, 2003

This should be the last week of vegetable harvest. The following crop could be late cotton planting or sudan grass. Few growers are planting cotton this late in Yuma area. We had in the past some growers who planted cotton the first week of May in eastern part of the county. Should cotton field be planted this week or next couple weeks, a choice of short season variety is important. Soil fertility and moisture level that favor rapid emergence and seedling development are also important.

Planted March 27-03

Planted February 10-03

There was no replanting this year. All planted cotton fields are progressing well despite average lowers temperatures. Fig above shows two planting dates of cotton in Yuma area. Both planting dates show good seedling development and stand. Cotton field planted on February 10 is already 10 inches high. Evaluating stand population and plant conditions is important to early crop management. Young seedling health and vigor should be evaluated by inspecting seedling both above ground and below ground. Plant should be checked for diseases. A vigorous and healthy seedling should grow about one inch per day and tap root is expected to reach 12 inches at first true leaf (JCS 2000).

---

April 14, 2003

Seedling Diseases (fungi Rhizoctonia solani, Pvthium spp.)

There have been few cotton fields infected with Rhizoctonia fungi known as "dumping off". The presence of this fungus is not widespread in Yuma County, only few cases were seen. Rhizoctonia fungi infect many fields of vegetable and cotton crops. Causes of rhizoctonia include lack of rotation, excess moisture and low temperatures after planting. Symptoms of rhizoctonia fungi are shown in figure 1. The infection is characterized by a dark reddish brown rotted zone on the stem and root. Seed treatments with fungicides are effective. Since rhizoctonia fungi of cotton are different from those of other plant species crop rotation is also an effective control. However, In Yuma County cotton-cotton rotation system is rather an exception. Growers are still planting cotton, specifically in eastern part of the county. At this time of the season the choice of short season varieties is important. .

Figure 1. Rhizoctonia fungi symptoms of infected seedlings and healthy cotton seedlings. Yuma, AZ, 2003

---

April 7, 2003 Agronomy Update

Weather variability was observed this year in both Yuma Valley and Roll area. Recorded temperatures at Yuma Valley shown below indicate that soil temperatures at 4 inches below the soil surface remained lower than optimum until the third week of February in Yuma Valley. These cool temperatures delayed lettuce harvest and cotton planting. Figure 1 below shows some days with soil temperatures at 4 inches below 65F, favorable level for seed germination and seedling growth. Evaluating stand population and plant conditions is important to early crop management. Young seedling health and vigor should be evaluated by inspecting seedling both above ground and below ground. Plant should be checked for diseases. A vigorous and healthy seedling should grow about one inch per day and tap root is expected to reach 12 inches at first true leaf (JCS 2000). There are still some cotton fields to be planted behind lettuce and cole crops. Planting rate should be adjusted according to seed size, soil condition and late planting. More information is available at http://ag.arizona.edu/crops and weather data are also available at http://ag.arizona.edu/azmet/data/1403em.txt. For any comment, question or concern please contact Mohammed Zerkoune at zerkoune@ag.arizona.edu or call 928 726 3904.

Figure 1. Daily maximum, minimum and average air temperatures (top graph) and temperature recorded at 4 inches below the soil surface (bottom graph) from January first to April 6, 2003 at Yuma Valley Research Station. Days cannot be shown on x axis

---

March 31

Vegetable harvest is getting close to the end. There are fewer and fewer lettuce fields left to harvest, freeing land for cotton planting. Current and expected soil temperatures for the coming days in the Yuma area are favorable for cotton planting. Cotton follows lettuce and other vegetables in the crop rotation systems.

Research data indicate that nitrogen and phosphorus residuals from vegetable crop are enough to sustain cotton growth during early stage. At the early stage, cotton requires a small amount of nutrients to achieve normal growth. Residual nitrogen from vegetable fields often meets cotton nutrient demand during the entire cotton growing season. However, fertilizer adjustment should rely on soil test. It is important to keep in mind that when crop nutrient deficiency symptoms appear, the damage is already done. If the damage is severe, the correction is often irreversible.

Nitrogen is often side dressed, the amount of nitrogen fertilizer needed should be determined based on a soil test. Later in the season, nitrogen level in the plant is evaluated by petiole samples. The number of soil and plant tissue samples needed depends on field size and uniformity.

Several inexpensive petiole tissue test kits are available on the market. They are easy to use, fairly accurate and quick. Nitrate tissue evaluation could be determined in the field or in the office using sap samples. Collect the petiole samples when cotton plants are not stressed since water stressed petiole samples may tend to give high nitrate values.

Transplanted watermelon crop is progressing well. In the early watermelon planting first flowers are appearing. Cantaloupe planted on "Yuma bed system" is growing well and on time. It is too early to notice any sign of nutrient deficiency or disease or insect damage.

Three variety trials have been planted in Wellton, Yuma and Gadsden areas. If anyone is interested in visiting any of these trials, please contact Mohammed Zerkoune, Yuma County Cooperative Extension for more information, telephone: 928 726 3904. Zerkoune@ag.arizona.edu

---

March 24 Agronomy Update

Favorable temperatures at planting depth and vegetable harvest have been favorable to cotton planting which is progressing across the county. Early planting during the mid week of February and early Mach have germinated with a good stand. Cold temperatures recorded recently did not affect the cotton seed germination and stand.

The results of variety trials conducted in Somerton and Wellton areas are available at Yuma County Cooperative Extension mailto:zerkoune@ag.arizona.edu. They are also on the University of Arizona website http://ag.arizona.edu/azmet/cotton.htm. Cotton variety trial results from previous years are also available in both locations indicated above. If you have an email address and you would like to receive information using your email please mailto:zerkoune@ag.arizona.edu

Lettuce harvest is progressing toward the end. Cotton follows lettuce and other vegetables in the crop rotation systems. At the early stage, cotton requires a small amount of nutrients to achieve normal growth. Residual nitrogen from vegetable fields often meets cotton nutrient demand during the early stage. However, fertilizer adjustment should rely on soil test. It is important to keep in mind that when crop nutrient deficiency symptoms appear, the damage is already done. If the damage is severe, the correction is often irreversible. Nitrogen is often side dressed, the amount of nitrogen fertilizer needed to apply should be determined based on soil test or petiole tissue.

Several inexpensive petiole tissue test kits are available on the market. They are easy to use, fairly accurate and quick. Nitrate tissue evaluation could be determined on the field or in the office. Collect petiole samples when cotton plants are not stressed since water stressed petiole samples may tend to give high nitrate values.

Watermelon crop transplanting is in progress. Cantaloupes planted on "Yuma bed system" are growing well and on time. It is too early to notice any sign of nutrient deficiency or disease or insect damage.

Next mid season cotton workshop is scheduled for the second week of June, 2003. If you have any question or preferable subject you would like to be covered in the workshop, please contact Mohammed Zerkoune at mailto:zerkoune@ag.arizona.edu or call 928 726 3904

---

Crop advisory- March 10, 2003

Early cotton planting stared during the second week of February. Such an early planting is usually done on dry field. Seed are germinated by subsequent irrigation when temperatures reach the optimum level near 65 F at the planting depth. Some Yuma growers planted cotton on dry field during the week of February 10, 2003. Soil temperature at planting depth was still under the recommended level of 65 F. On February 12, 13 and 25, 2003, 0.17 and 0.62 and 0.45 inches of rain were recorded, respectively in Roll area. In Yuma area 0.31, 0.23, 0.03 and 0.58 inches of rain were recorded on February 12, 13, 14 and 25, respectively. I visited several fields where cotton was planted early in February and the cotton stand on these fields is not affected. The average stand per 10 linear feet observed in several locations was 55 plants or 72,600 plants per acre. In an early planting variety trial near Somerton, a significant stand difference was observed among 8 varieties tested. The stand is currently from 39.7 to 58.7 plants per 10 linear feet or 52,404 to 77,484 plants per acre. It should be noted that planting rate was not adjusted for seed size and the germination is not complete yet for some varieties. Further counting is necessary when germination is completed to determine the final stand population for each variety tested. Cotton planting has resumed this week since the soil temperature near planting depth is above the 65F. Several temperature readings were made on Sunday February 9, 2003 between 1 and 4 pm at various locations in the valley and indicated that temperatures at planting depth are above 70 F. Melon crops are progressing well for both planting systems. Early planting under plastics is at an advanced stage and melon planted under Yuma Bed technique has germinated with a good stand. Iceberg lettuce, broccoli and cauliflower are approaching the end of the season. Harvest of leaf lettuce, romaine and herbs are still in progress.

Next mid-season cotton meeting is scheduled for the second week of June, 2003.

Insect, nutrient management, irrigation and weed control will be the focus of this coming workshop. We would like to hear from everyone who has a concern, comment, suggestion regarding cotton and commercial vegetable production please contact Mohammed Zerkoune by email: Zerkoune@ag.arizona.edu or call 928 726 3904.

---

March 17, 2002 Agronomy Update

Cotton planting season resumed and actively continues as soil temperatures rise in Mid-February in Yuma and the first week of March in Roll area. Due to the low temperatures recorded last week, growers wait for warmer weather before they resume planting. Cotton follows vegetables in the crop rotation system. At the early stage, cotton requires a small amount of nutrient to achieve normal growth. Residual nitrogen from vegetable fields often meets cotton demand during the early stage. However, fertilizer adjustment should rely on soil test. It is important to keep in mind that when crop nutrient deficiency symptoms appear, the damage is already done. If the damage is severe, the correction is often irreversible. Cotton planted two weeks ago started to emerge well despite low temperatures during last month. Planting has resumed across the county. The results of variety trials conducted in Somerton and Wellton areas are available at Yuma County Cooperative extension mailto:zerkoune@ag.arizona.edu. They are also on the University of Arizona website http://ag.arizona.edu/azmet/cotton.htm. Cotton variety trial results from previous years are also available in both location indicated above. If you have an email address and you would like to receive information using your email please mailto:zerkoune@ag.arizona.edu

Watermelon crop transplanting is in progress. Cantaloupes planted in Yuma bed had their beds shaped. At this point crops look good and vigorous. It is too early to notice any sign of nutrient deficiency or disease or insect damage. Peer to peer virus diseases management project has started in Yuma. The project includes growers, PCA and University of Arizona faculty. The execution method was inspired from the seed isolation pinmap developed by the Cooperative Extension. http://img.calsnet.arizona.edu/website/yuma/viewer.htm

Our Cotton educational meeting is scheduled for the second week of June, 2003. Please help us to serve you better. If you any question, comments, suggestion regarding cotton and vegetable research and extension program please mailto:zerkoune@ag.arizona.edu or call 928 726 3904 or 928 580 0222

---

August 18, 2002 - Agronomy Update Overall, this cotton season has been good with good fruit retention and without a serious insect pressure offering a good yield. Heat Units are running only one day late behind normal. Most of cotton planting date should have reached a termination stage. At this time, all crop monitoring regarding a balance between vegetative growth and reproductive "sink" should have been achieved. It is time to focus on the finish line, which consists of taking the formed bolls to maturity with a good combination of irrigation and defoliation management. For the remaining cotton season, focus should be on irrigation termination, defoliation and some late insect outbreak. Even at this cotton stage, insects can be a problem. They still need to be monitored even after defoliation application. Water stress promotes plant senescence, but good plant water potential should be maintained to keep the leaves physiologically active with enough leaf weight to break and drop. Soil water holding capacity, the amount of the previous irrigation water, weather conditions and plant canopy need to be included in the irrigation termination decision. The University of Arizona recommends that the timing for defoliant application should take into account several factors. Last irrigation should be based upon maturing the fruit intended for harvest. The process of defoliation consists of speeding up a natural physiological process of plant aging, which results in leaf drop. Plant-Water relation is important to understand at the time defoliant is applied. University of Arizona research data showed that period separating last irrigation and defoliant application should be about twice as much as the time separating two late-season irrigations.

Upcoming Events: 8/21/02 Pre-season Vegetable Workshop; Yuma County Extension Office; call 928-726-3904 to register 12/04/02 Desert Crop workshop; Yuma Civic Auditorium--mark your calendar

---

August 11, 2002 Agronomy Update Overall, this cotton season is characterized by good fruit retention, offering good yield potentials. Insect pressure has not been a serious problem. Most of the cotton fields planted before the first week of April reached the cutout. Cutout is reached when cotton plant completes the flowering. It has been observed that cutout starts when 2500 HU have been accumulated after planting. Cutout is also observed when here are five nodes between the uppermost white flower and the last fully expanded leaf (with one inch diameter). Cotton fields planted early are initiating the open bolls. Cotton plants have overall a good boll load. At this time, all crop monitoring regarding a balance between vegetative growth and reproductive "sink" should have been achieved. It is time to focus on the finish line, which consists of taking the formed bolls to maturity with a good combination of irrigation and defoliation management. Last irrigation should be based upon maturing the fruit intended for harvest. Water stress promotes plant senescence, but good plant water potential should be maintained to keep the leaves physiologically active with enough leaf weight to break and drop. Soil water holding capacity, the amount of the previous irrigation water, weather conditions and plant canopy need to be included in the irrigation termination decision. In the Yuma area, the vegetable planting season often determines the cotton harvest date. However, an early irrigation termination results in leaf burn and desiccation may not allow cotton bolls to fully develop and reduces yield. University of Arizona research data showed that period separating last irrigation and defoliant application should be about twice as much as the time separating two late-season irrigations.

Upcoming events: 8/21/02 Preseason Vegetable Workshop; Yuma County Extension office, call to register.

---

July 21, 2002 Agronomy Update Cotton crop fertilizer program should have ended for this year. For early planting, accumulated heat units reached 2696 units for Roll and 2835 units for Yuma. For the latest planting, the accumulated heat units reached 2224 units for Roll and 2315 units for Yuma. Most of cotton fields planted early and mid-planting season are going toward cutout. Cutout can be easily monitored by counting the number of nodes above the top first position white flower (NAWF). NAWF of 5 or less indicate that crop is progressing toward cut out. Overall cotton crops are progressing well this year. Fruit retention is very good across Yuma County. Cotton fields planted seem to carry an adequate fruit load leading to good yield. Little insect pressure has been observed. Where insect pressure has been observed, insecticide application had success on keeping insect pressure down. Focus is now on irrigation and insect control especially for the late planting crops.

Events: Pre-Season Vegetable Workshop; August 21, 2002

---

July 7, 2002 Agronomy Update No serious insect pressure has been observed yet. The combination of rising temperatures and high humidity during Monsoon season will more likely generate heat stress and insect pressure on cotton crops. However, insect pressure is field specific, scouting for insect pressure is needed to make insect management decision. Temporal and spatial insect distribution complicates the prediction of whitefly infestation in a given field. It is, therefore, important to determine the whitefly pressure by sampling fields weekly for adults and nymph whitefly infestation. Whitefly sampling method is outlined in http://ag.arizona.edu/crops/ or contact Yuma County Cooperative Extension office for more information. The industry developed effective insecticides to control whitefly. Fruit retention is subject to good vigor and maturity development. Nitrogen and irrigation stress should be avoided. Both soil sampling or petiole testing are effective testing tools for nitrogen management decision. Water use is estimated at 2.16" for cotton fields planted during the week of 4-1-2002 and 2.51" for the fields planted during the week of 2-1-2002.

Events: 08-21-2002. Pre-Season Vegetable Workshop: Yuma Cooperative Extension auditorium 12-04-2002. Desert Agriculture Conference: Yuma Convention Center

---

June 30, 2002 Agronomy Update Cotton crop is continuing to grow without any significant problems. Some observations collected across the county show cotton height is between 30 to 48 inches and 12 to 21 nodes (height/node ratio 2.3 to 2.4). Data is from just few observations collected from Yuma cotton fields, and not meant to be an average across the county. It is important to continue observing cotton growth and pay attention for changes in fruit retention and height node ratio and detect any changes in fruiting and vigor. Overlapping whitefly hosts include cotton, melon and alfalfa. Whiteflies migrate from terminated crop to the growing crop. Insect pressure is moderate up to now, and no outbreak has been observed yet. However, the month of July and August are important to watch. Frequent and adequate scouting is necessary for monitoring the insect pressure and treat when necessary. I collected some cotton petiole sap samples across the county. The petiole nitrate-nitrogen values were from 1500 to 2000 ppm. They are in sufficient range. Petiole sampling should continue and fertilizer should be applied as needed to avoid nitrogen deficiency that may induce yield reduction. With current high temperatures across the county, cotton plant will grow rapidly. Water demand will increase as result of rapid growth and high evaporation. For additional information regarding this crop advisory or any other information you may need, contact Yuma County Cooperative Extension or visit University of Arizona Website http://ag.arizona.edu/crops/

Coming events: On-Line Pinmap for vegetable seed, July 1 2002; Pre-season Vegetable workshop: August 20, 2002 Desert Agriculture Conference December 4, 2002

---

June 23, 2002 Agronomy Update Most of the fields that needed balance between vegetation growth and fruit setting have already received Pix applications. Until now, crop conditions and yield potential are favorable for the majority of the fields. Cotton crops planted during late February have developed bolls, 10 to 13 nodes and high/node ration 2 to 2.5. Late cotton crops planted in April are blooming. All cases, a management that enhances fruit setting and fruit retention is critical. Proper insect scouting, adequate nutrition and optimum soil moisture are the most important field management components leading to a high yield and fiber quality. Melon growers are finishing last harvest. Displacement of whiteflies from harvest melon fields to neighboring cotton fields is more likely to occur. We need to observe such a white fly movement by adequate scouting and decide on treatment dictated by the degree of insect pressure. For more information please visit http://ag.arizona.edu/crops or contact Yuma County Cooperative Extension.

Upcoming Events: July 1 2002, Pinning map opened on line August 20, Pre-season Vegetable Workshop

---

June 16, 2002 Agronomy Update Recent hot and dry weather conditions have been favorable for rapid cotton crop development. Early cotton planting has already reached boll setting. Currently 20 to 25 % of cotton acreage has reached the boll setting. Most of remaining acreage has reached squaring stage. As we continue to experience hot and dry weather conditions through the summer, one critical point to consider is to maintain adequate soil moisture all the time during the remaining of the season. Cotton crop sustains hot and dry weather conditions and continues to grow, set and hold fruits providing sufficient soil-water. Plant stress should be avoided. Soil water level should be checked for irrigation when soil water reaches 40-50 % depletion level. Several methods exist to check for soil moisture. If you need any help how to collect, process and interpret the results contact Yuma County Cooperative Extension. Substantial amount of N residual is left behind produce precedent cotton. In addition cotton in early stage needs a small amount of N for normal growth. Thus N fertilizer is rarely applied at planting to cotton that follows produce in the rotation. University of Arizona recommends that for optimum efficiency of fertilizer nitrogen use by crops, application of N (50-75 lb N /A should be made in split applications before peak bloom. No serious insect pressure has been observed yet. Growers should remain vigilant to monitor any outbreak that may occur.

Upcoming events: June 21, 2002 at Arizona Western College, electronic Pinning map training. Week of August 19, 2002: Vegetable workshop. For further info about events, contact Mohammed Zerkoune.

---

June 9, 2002 Agronomy Update Cotton crops are transiting from vegetative to reproductive growth. Maximum yield depends on the fruit setting and maintenance of fruit set to achieve maturity. Cotton bolls are forming from early planting. Late planting reaches pin stage. Temperature recorded last week was above normal. However, HU run two days behind in Yuma Valley. Weather forecast indicates that temperatures will be above 100 F during this week for both Yuma Valley and Wellton area. With favorable weather for fruit set and development, the identification of causes of square loss is important. Lygus is the number one square-feeding insect pest, particularly in near non-cotton host. Melon and watermelon crops for example are reaching the end season. Pests common to these crops migrate from melon to have refuge in cotton crops. The use sweep net samples are good methods of identifying and quantifying lygus in the fields when sufficient samples are collected. More information can be found at http:ag.arizona.edu/crops or contact Yuma Cooperative Extension. The rising temperatures will increase water demand as a result of evaporation and rapid plant canopy development. Early water stress should be prevented to avoid fruit loss. Adequate nutrition particularly nitrogen should also be provided to increase plant vigor and plant growth. Soil moisture and plant nutrition should be monitored regularly.

---

June 2, 2002 Agronomy Update Cool weather and late lettuce harvest during mid-February and March induced a slight delay in the cotton planting date. Cotton planted in mid-February is beginning to show its early flower in the county. Early fruiting and early fruit retention are conducive to high yields. However, cotton fields should be monitored to identify the first fruiting branch and the square/boll retention. In coming days, crops are expected to grow rapidly with the increase in temperatures and HU accumulation; fruit retention level should be monitored and identify the causes leading to fruit dropping. Adequate plant nutrition, soil moisture and pest control are paramount to high yield. Detailed information regarding plant nutrition, irrigation and integrated pest management for cotton can be obtained at http://ag.arizona.edu/crops or contact Yuma County Cooperative extension Office at 928-726-3904 or email me at zerkoune@ag.arizona.edu Should petiole samples be collected, it is important to collect a large number of samples then mix to form a composite sample. The number of samples needed per composite increases with the size of the field and its variability. At least one composite sample is needed for every manageable field. It is also important to collect petiole samples from newly matured leaves. The availability of new and inexpensive laboratory instrumentation improved the analytical procedure's accuracy. The quality of sampling cannot be overemphasized, since the errors associated with the field sampling are greater than the errors associated with laboratory procedures. Melon harvest has begun in Yuma; as the melon season progresses toward the end, whitefly migration from melon fields to cotton fields is expected. One should monitor closely the whitefly population, evaluate the degree of infestation and observe a good integrated pest management. For more information regarding scouting and evaluation of insect infestation, contact the cooperative extension office or visit the University of Arizona web site listed above.

---

May 19, 2002 Agronomy Update Fields are planted to cotton after vegetables are picked. Early cotton planting during the second week of February is reaching the pinhead square stage. The height/node ratio is about 1.5. Growth rate, plant vigor and stand establishment are influenced by accumulated heat units, available soil water, and plant nutrition. Heat unit (HU) are running two days behind normal for Yuma. Detailed information on HU and water use is available at http://ag.arizona.edu/Azmet/cotton.htm weather update below, click on Roll or Yuma. Petiole samples from selected fields in Yuma indicated that nitrate-N level is adequate. Figure below shows deficient, adequate and excess petiole range as function of heat units. Nitrate-N concentration is also affected by plant age http://ag.arizona.edu/crops/cotton/soilmgt/nitrogen_management.html.As a plant ages and accumulated HU increases, nitrate concentration decreases. Nitrate-N status can easily be monitored by collected sufficient petiole samples submitted for laboratory analysis. Sufficient samples should be randomly collected across the field at the time when plants are not stressed.

Upcoming Events May 29, 2002 - Annual Melon Day; 9:00 a.m. - 12:00 noon; Maricopa Ag Center June 12, 2002 - Midseason Cotton Workshop; Yuma County Cooperative Auditorium. June 18, 25; July 2, 9 - Ag Course in Soil Science (SWES 406 - Soils & Soil Fertility). Offered for 1 credit at the Yuma County Cooperative Auditorium 12:00 - 4:00 pm on the above mentioned dates.

---

May 12, 2002 Agronomy Update Fields are planted to cotton after vegetables are picked. Early cotton planting during the second week of February is reaching the pinhead square stage. The height/node ratio is about 1.5. Growth rate, plant vigor and stand establishment are influenced by accumulated heat units, available soil water, and plant nutrition. Heat unit (HU) are running two days behind normal for Yuma. Detailed information on HU and water use is available at http://ag.arizona.edu/Azmet/cotton.htm weather update below, click on Roll or Yuma. Petiole samples from selected fields in Yuma indicated that nitrate-N level is adequate. Figure below shows deficient, adequate and excess petiole range as function of heat units. Nitrate-N concentration is also affected by plant age http://ag.arizona.edu/crops/cotton/soilmgt/nitrogen_management.html.As a plant ages and accumulated HU increases, nitrate concentration decreases. Nitrate-N status can easily be monitored by collected sufficient petiole samples submitted for laboratory analysis. Sufficient samples should be randomly collected across the field at the time when plants are not stressed.

Upcoming Events May 29, 2002 - Annual Melon Day; 9:00 a.m. - 12:00 noon; Maricopa Ag Center June 12, 2002 - Midseason Cotton Workshop; Yuma County Cooperative Auditorium. June 18, 25; July 2, 9 - Ag Course in Soil Science (SWES 406 - Soils & Soil Fertility). Offered for 1 credit at the Yuma County Cooperative Auditorium 12:00 - 4:00 pm on the above mentioned dates.

---

May 5, 2002 Agronomy Update Total N requirements will vary among fields. Total nitrogen applied should be based on realistic yield goal using an N factor of 60 lbs N per bale of cotton. Most cotton crops are planted after vegetables leaving behind a substantial amount of residual nutrients. During the cotton early stage the nutrient requirement is small. Nitrogen is generally not applied prior cotton planting. As cotton plant develops, nitrogen management should be carefully monitored.

---

April 28, 2002 Agronomy Update Early planting should be starting to develop nodes by now and will proceed rapidly as the temperature increases. Research work in Arizona indicated that the development of one cotton-node requires 100 heat units (HU). Cotton requires a small amount of nutrient at the early stage. In general, at this stage, residual fertilizer from previous crops (vegetables) supply adequate amount of nutrients for cotton. As cotton plant develops, nutrient balance and water supply need to be monitored attentively. Melons, alfalfa and cotton are concurrently grown in Yuma County. There is a posibility of inter-crop movement of whitefly. It is important to monitor and control the whitefly pressures on the crops. More information can be obtained at Http://ag.arizona.edu/crop

Events: May 7th, AgriLogic, Inc. will hold a listening session at the Shiloh Hotel at 8:00 a.m. Purpose of the meeting is to gather input concerning the feasibility of a risk management strategy, with a focus on crop insurance.

---

April 21, 2002 Agronomy Update At this time, most of the cotton fields have been planted. If fields are still to be planted, special considerations should be given to selection of varieties. Short to medium maturity types should be considered. In addition, where replanting appears to be necessary during the next week or two, the choice of variety becomes increasingly important as we are approaching the end of planting season. Cotton planted in mid-February has reached five-leaf stage. Cotton planted during the first week of April is at two-leaf stage. The growth rate for early planting appeared to be slow this year because of low temperatures. The cotton growth rate will increase with temperatures during the next week or two. Start to carefully observe insect pressures, nutrient balance and water demand.

Upcoming Events: May 7th at 8:00 a.m. at Shiloh Inn, Yuma. AgriLogic, Inc. will hold a meeting to gather input from interested parties concerning the feasibility of a risk management strategy with a focus on crop insurance for vegetable crops.

---

April 14, 2002 Agronomy Update Weather variability was observed this year in both Yuma Valley and Roll area. Recorded temperatures at Yuma Valley and Roll indicate that temperatures 4 inches below the soil surface remained lower than the optimum until the third week of February in Yuma Valley and after the third week of March in Roll area. These cool temperatures delayed lettuce harvest and cotton planting. Evaluating stand population and plant conditions is important to early crop management. Young seedling health and vigor should be evaluated by inspecting seedling both above ground and below ground. Plant should be checked for diseases. A vigorous and healthy seedling should grow about one inch per day and tap root is expected to reach 12 inches at first true leaf (JCS 2000).

---

April 7, 2002 Agronomy Update Cotton crop is planted behind vegetables that leave enough N and P residual for the initial cotton growth. However, soil testing is recommended to make sure that adequate nutrients are available for good plant vigor and a stand establishment. Cotton is planted on dry soil then germinated by irrigation. When cotton is planted on wet soil, it is necessary to make sure that soil moisture is adequate.

---

March 31, 2002 Agronomy Update Planting date is becoming increasingly important in the desert southwest where vegetables are dominant crops. The importance of the earliness is two-fold: 1. avoid late season humidity, heat stress and insect pressure and; 2. free the ground early at the end of the summer for vegetable planting. In any case, during early stage, effort should be made to maintain vigor and healthy plants conducive to fruiting cycle, completion yield and low micronaire. Although early cotton plants require a small amount of nitrogen, plant and soil samples should be collected and sent to commercial laboratory for fertilizer adjustment.

---

March 24, 2002 Agronomy Update Choice of cotton varieties, soil temperature and planting depth are the factors that influence seedling vigor and plant stand. In conditions of cool soil temperatures or unfavorable 5-day forecasts, avoid planting varieties that are known to have less than optimum seedling vigor. These varieties should be planted when soil temperature is 65F or greater. Planting depth less than 2 inches is preferred.

Events: Field day - Alfalfa Weed Control, April 3rd, 9:00 - 11:00 a.m. in Yuma (Avenue 6 1/4E & 32nd Street) and again from 2:00 - 4:00 pm in Ehrenberg (Tsosie Road & Rovey Equipment yard). Call Extension office for details.

---

March 17, 2002 Agronomy Update Cotton planting season started in mid-February in Yuma and the first week of March in Roll area. Due to the low temperatures recorded last week, growers wait for warmer weather before they resume planting. March 10, 2002 Agronomy Update At the early stage, cotton requires a small amount of nutrient to achieve normal growth. Cotton follows vegetables in the crop rotation system. Residual nitrogen from vegetable fields often meets cotton demand during the early stage. However, fertilizer adjustment should rely on soil test. Cotton planted two weeks ago started to emerge well despite low temperatures during last two weeks.

Upcoming Events: March 19, 2002. Yuma County Auditorium. Whitefly Workshop 8-1PM. 3 credits for AZ; 3.5 credits for CA and 4 credits for CCA. Call M. Zerkoune at Yuma County Cooperative extension Office for additional info on this event.

---

March 4, 2002 Agronomy Update Cotton follows lettuce in the crop rotation systems. Residual nitrogen from lettuce crop often meets cotton demand during the early stage. However, fertilizer adjustment should be based on soil test.

Upcoming events: March 19, 2002. Yuma County Auditorium. Whitefly Workshop 8-1PM. 3 credits fot AZ; 3.5 credits for CA and 4 credits for CCA; Call M. Zerkoune at Yuma County Cooperative extension Office for additional info on these events.

---

February 25, 2002 Agronomy Update In the early stage of planting it is important to monitor soil temperature at the planting depth and watch the weather forecast. Temperatures below 55F have detrimental effects on seed germination rate, seedling diseases and poor stand. Soil temperature is highly variable since it is affected by the soil type and management. It is advisable touse soil termometer to check soil temperature of a particular field. The first irrigation following planting on dry field will cool seedbeds substantially. Cotton follows lettuce in the crop rotation systems. Residual nitrogen from lettuce crop often meets cotton demand during the early stage. However, fertilizer adjustment should be based soil test.

Upcoming events: March 19, 2002, Yuma County Auditorium. Whitefly workshop 8-1 pm, 3.5 credits granted. Call M. Zerkoune at Extension Office for additional info on these events.