[Arid_gardener] Re: Citrus: Watering and Fertilizing

[Olin Miller]

----- Original Message ----- From: <lynreys2002 at yahoo.com>
Sent: Friday, June 29, 2007 5:27 PM
> Carol L Reynolds
> 85381
> lynreys2002 at yahoo.com
> When is the best time to fertilize rose bushes?  To cut back your roses?
> When should you fertilize citrus trees and best watering of citrus trees?
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Fertilizing Citrus
============
Our usual recommendation is three times per year - February, Memorial Day,
Labor Day.  The amount depends on size and age of the tree.  The bag label
for ammonium sulfate normally will not recommend its use as a citrus
fertilizer so the amount is usually based on the nitrogen content.  One old
rule for standard citrus trees was to apply ammonium sulfate (21-0-0-24S)
from zero to 7.5 pounds per year linearly from planting time up to 6 years,
then maintain the 7.5 pounds per year thereafter.  Use 1/3 of this amount at
each of the three times.  Some people also measure the amounts using kitchen
utensils.  One problem with ammonium sulfate is that it does not replenish
other essential elements like phosphorus, iron, zinc, and manganese which
are required for effective nitrogen utilization. After a few years these
elements can be depleted and the citrus tree and fruit will exhibit nutrient
deficiencies. Ammonium sulfate is the least expensive fertilizer but the old
adage that "good fertilizer is not cheap and cheap fertilizer is not good"
may apply.

The simplest and easiest method is to use a citrus fertilizer which in
addition to nitrogen also contains the appropriate amounts of P, Zn, Fe, and
Mn.  Some are "formulated for Arizona soils".  Application rates are
indicated on the fertilizer bag.  Typical N-P-K  percentages may be 16-8-8.
It can become a bit technical because the P and K percentages indicate the
percentages of the compounds and not the elemental values, e.g.,
16N-8P2O5-8K20) where phosphorus pentoxide contains only about 44 %
elemental phosphorous and potassium oxide from 19 to 52 percent potassium
depending on which compound is used to represent potassium oxide.  But
homeowners don't need to worry about that - just follow the instructions on
the ferilizer bag.

Irrigating Citrus
============
 For established trees water every 10-14 days in the summer and monthly in
the winter.  refer to  "Table 2. Application Intervals for Irrigated Citrus
Trees" at
http://cals.arizona.edu/pubs/crops/az1151.pdf
for your trees' age and size.  With our unusually high heat, I have been
watering my 25 year old standard trees weekly for the past month.  Mulching 
in the basin helps reduce evaporation.

The above are the opinions of this author and do not necessarily represent
the opinions or recomendations of the U of A Cooperative Extension.

Olin Miller, Master Gardener Volunteer
U of A Cooperative Extension, Maricopa County AZ