The Cross Section, Volume 33, Number 3, March 1987 Page: 3
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March 1987 THE CROSS SECTION Page 3
Fertilizers Affect Cotton Water-Use
Efficiencies
"It is commonly assumed that if a
field crop such as cotton did not have
the proper amount of nutrients it
needed for growth, the plant would
just sit there and do nothing," says
Dr. Charles Wendt, Professor of Soil
Physics at the Texas Agricultural
Experiment Station in Lubbock.
However, results from a 1986
container-grown cotton study
conducted at the Experiment Station
show that this is not the case.
"A nutrient deficient plant may
visually just sit there and do nothing,
but it is continually drawing
moisture from the soil profile in an
attempt to obtain the nutrients it
needs for growth. Since water is
used with little or no growth, water-
use efficiency is drastically reduced."
Due to rainy weather the study
was not initiated until July, notes
Wendt. "However, the differences in
water-use efficiency that we
observed due to the various fertility
treatments were dramatic."
Container-Grown Cotton Studios
During the 1986 cotton season,
Wendt and Dr. Arthur Onken, a
Professor of Soil Chemistry also with
the Texas Agricultural Experiment
Station, conducted experiments on
container-grown cotton to determine
the influence of water levels and
fertilizer treatments on the water-useefficiency of cotton.
The studies were conducted under
a rain-out shelter to control moisture.
The cotton was planted in plastic
containers filled with a soil that was
deficient in both nitrogen and
phosphorus.
The experiments involved two
water treatments and four fertility
treatments for a total of eight
treatment combinations.
The water treatments were re-
placement of 100 percent of the
evaporative demand and replace-
ment of 50 percent of the evaporative
demand.
The fertility treatments consisted
of a control to which nothing was
added, a treatment of nitrogen at 160
pounds per acre, a treatment of
phosphorus at 160 pounds per acre,
and a treatment of nitrogen plus
phosphorus at 160 pounds per acre
each. (It is normal research practice
to use higher fertilizer rates in
container studies than normally
would be used in field production
due to restricted soil volumes.)
Every two weeks, approximately
64 plants were harvested and tissue
analyses made to determine nitrogen
and phosphorus levels in the plants.
Treatment Reispcnesu
The researchers observed no
response to the application ofnitrogen alone. In fact, there was
probably a slight depression of
growth in the plant in response to
the application of nitrogen alone.
Significantly less water was
required to produce dry matter in the
phosphorus and phosphorus plus
nitrogen treatments, and under these
treatments the plants produced more
fruit.
The accompanying graphics
illustrate dry matter and water data
obtained during the study.
The most efficient use of water and
the highest yield was observed in the
nitrogen plus phosphorus high-water
(NPH) treatment. Good water-use
efficiencies were also observed
under the nitrogen plus phosphorus
low-water (NPL) treatment and under
the phosphorus high-water (PH)
treatment.
Primarily, the study points out the
need to have a balanced fertility
program to get the most efficient use
of water.
In analyzing the data, Wendt
observes, "It appears that you have
to have phosphorus to achieve
nitrogen uptake. You also have to
have water for nutrient uptake. We
still need to find out just how to
balance our fertility against our
water supplies," states Wendt.
Other observed responses include:
Both water level and fertilityaffected water-use efficiency.
The control low-water treatment
(CL) showed a fairly good water-
use efficiency, but did not produce
much dry matter. In general, the
water requirement increased as
the fertility level decreased.
The researchers did get fruit
production where phosphorus
either alone or in combination
with nitrogen was applied.
However, they did -not get fruit
production where phosphorus
was not applied.
The researchers observed that the
top, root, and total plant weights
were significantly higher in the
high than in the low moisture
levels.
Summary
Wendt reports that the fertility
data from the 1986 container-grown
cotton studies show that fertilizers
can have an impact on water-use
efficiency. Additionally, he notes
that nitrogen alone had no effect
on growth and water-use efficiency.
The addition of phosphorus and
nitrogen plus phosphorus signifi-
cantly increased the weight of the
plant parts and fruit and decreased
the amount of water required to
produce dry matter while increasing
the production of fruiting parts.
-KRCotton Response To Fertilizer/High Water Treatments
Cotton Response to Fertilizer/Low Water Treatments
Treatment
NPL
- PL
'---- NL
--CLWater
Requirement
(gH20/gDM)
323
341
478
344Water-Use
Efficiency
(gDM/kgH20)
3.1
2.9
2.1
2.1451
F
40-
Water
Requirement
(gH2OfgIIM)
285
423
159
743Water-Use
Efficiency
(gDMlkgH20)
3.5
2.4
1.,6
l..335k
30
201-
25
0)
wJ
020
15-
151
..
.-
w
I-
H
Q
0Trea'lient (gIH201g1M (gDMkg H2
MP1 285 3.5
P14 423 2.4
NH- EiS9 1.8
CM 743 t3
MN Nqlrogen
- P - Pbosphorua
- -IM - M4Iliu Waler
- ---''C - Conirol,- L 3472.
,-CL 344 2-9
N ir
P rhs
L Lw
-C n5F
0
N - N iiogen
P-Piphorus
L- Lo Water
SCntrol0
1 2 3 4 5 6 7
TRANSPIRATION (kg)10-
5
n--
0 2 4 8 8 10 12 14
TRANSPIRATION (kg)March 1987
T HE CR O SS S EC T IO N
Page 3
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High Plains Underground Water Conservation District No. 1 (Tex.). The Cross Section, Volume 33, Number 3, March 1987, periodical, March 1987; Lubbock, Texas. (https://texashistory.unt.edu/ark:/67531/metapth1533144/m1/3/?rotate=180: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.