[Arid_gardener] Re: Depleted Soil, Fertilizer, Water

[Olin Miller]

The symptoms you describe suggest either a lack of nutrients or not enough
water, or both.

Soil pH regulates how well plants can absorb nutrients.  Native desert soils
in the valley are alkaline, around pH 8, which is too high for most
fertilizers.  There is a product named Dispersol, available at garden
centers, that can help to rapidly lower the soil pH.  Granular soil sulfer
is also very good and persists longer in the soil.  Composted animal manures
are good organic soil amendments that help condition the soil but are poor
fertilizers.  For example, the N-P-K percentages of of cow manure range from
(0.5 - 0.2-0.5 ) to (1.3- 0.9-0.8).  Compared with ammonium sulfate at
21-0-0 it would take from 16 times to 42 times more cow manure, by weight,
for the same amounts of nitrogen.

Inorganic fertilizers are effective and inexpensive.  Some organic
fertlizers are also effective for nitrogen but many of the popular phosphate
fertilizers are ineffective in our alkaline soil.  For example, from a
discusssion on arid_gardener back in December 1996, according to Tom Doerge,
Agronomy Research Scientist, "...  rock  phosphate is so insoluble in
alkaline soils that it is of little or no value as a source of plant
available phosphorus ...".  This may explain why it isn't easy to find in
Phoenix.  Bone meal from slaughtered animal boes, is also often recommended
as a phosphate fertilizer but in has a high calcium content in the form of
calcium carbonate (as in lime and caliche) that would make it ineffective in
our soil.  There have also been concerns about BSE in bone meal (as in mad
cow) when it is fed to cows  but it is probably okay if it has been steamed.

Bedding plants set out  before the daytime highs dropped into the 80s would
have had a hard time coping with the hot weather.  Light sprinkling in the
early morning to freshen the foliage and blooms and flooding the root zone
every few days could have helped,  but it may have just have been too hot
for the plants.  I also lost most of my early lettuce transplants despite
watering.

With cooler temperatures, your Bermudagrass lawn will stop growing and go
dormant.  It will not green up again until April.  Water occasionally during
the winter months to keep the roots from drying out.  But in the summer it
needs water - lots of water.  Your observation that it there is some grass
growth by overwatering suggests that it received almost enough water.  In
the summer months, newspaper weather pages recommend watering every three
days to replace the water lost (in inches) the previous three days.
Historical data stated as  ET  rates (for water loss due to evaporation and
transpiration) at the AZMET site (  http://cals.arizona.edu/azmet/  )
indicate an average monthly ET over 10 inches for my area of Phoenix which
translates to about one inch every three days.  The AZMET site also has
information about ways to measure the water applied but a simple guideline
is that after watering, a slender rod should be inserted easily to about one
foot.

Publication AZ 1151 at
http://ag.arizona.edu/pubs/crops/az1151.pdf
contains a chart with recommended watering intervals for the various stages
of growth of citrus trees.  There is also a chart showing the amount of
water loss per day for tree sizes from 2 feet to 30 feet canopies.  To find
the total amount required, multiply the watering interval in days by the
daily amount of water lost  (= replacemet water needed).  But as a practical
matter, the slender rod method also works for citrus -  easy penetration to
one foot the first year gradually increasing to 3 feet after a few years. Be
sure to water deeply every irrigation. This helps encourage deep root
growth.  With drip irrigation, emitters should be spaced evenly at and
around the canopy of the tree to ensure there will be no gaps in underground
root development.

Olin Miller, Master Gardener Volunteer, Maricopa County AZ
http://home.att.net/~millero/ValleyOfTheSunGardeners.htm

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----- Original Message ----- From: <trainhr1 at cox.net>ent

Sent: Monday, October 16, 2006 10:00 AM
> ...We recognized that the soil was depleted, so I have been using manure
> and mulch to help in a flower garden. Despite my efforts, most of the
> flowers die off. In checking with my gardening books and this website, I
> was advised to check the roots. When I do, I find the plants have no
> roots. Most of the flowers I have put in seem to start well and then get
> sickly and dry up. When I check to see what happened, the plants  seem to
> have a stunted root system if any roots at all.
>
> Most of the grass, except at the edges and in the garden has died off. If
> I overwater, then we get some grass growth. It's a Bermuda grass with a
> root system that is unbelievable often extending several feet before
> popping out of the ground.
>
> Currently, the only healthy plant is verbena. I have a couple of mum
> plants that are stunted, but most died. My citrus trees aren't growing as
> fast as they should. The cacti are doing better now that we have had all
> the rain.
>
> We have changed the watering system to a drip system recently. I was
> hoping that getting the right amount of water to the plants would help,
> and it has to a certain degree. The plants, however are still not strong
> or big.