AGRONOMIC EVALUATION OF PHOSPHATE SOURCES FOR SOYABEAN PRODUCTION IN THE NIGERIAN SAVANNA ALFISOL
AGRONOMIC EVALUATION OF PHOSPHATE SOURCES FOR SOYABEAN PRODUCTION IN THE NIGERIAN SAVANNA ALFISOL
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Date
1997-10
Authors
PAM, ESTHER DABALI
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Abstract
In the Northern Guinea Savanna, phosphorus deficiency has
been identified as the most important single element
limiting the growth of soyabean. Furthermore, soyabean
producers are constrained by the high cost of commercial
Single Super-phosphate fertilizers hence the need to
identify alternative, cheaper and effective sources of
phosphorus that will be within the reach of poor resource
farmers. A field trial conducted for two cropping seasons
(1994-1995) on two different sites at the Institute for
Agriculture Research Farm, Samaru to evaluate the effect of
four sources of phosphorus, viz: single superphosphate,
partially acidulated phosphate rock (50%), Sokoto phosphate
rock and Togo phosphate rock on the performance of soyabean.
The phosphorus rates were 0, 30, 60, 120 kg P205 ha"1.
Soyabean cultivar Samsoy 2 was used as test crop. All
treatments were replicated three times in a randomised
complete block design.
Soyabean grain yield and yield components responded
significantly (P = 0.01) to P fertilizer application. The
number and weight of nodules, number of flowers per plant,
shoot dry weight were increased, but reduced root weight
with increasing rates. The increased nodulation resulted in
increased number of pods and seeds per plant, weight of
seeds per plant, 1,000 seed weight and threshing percentage
of the crop. The eventual effect was a highly significant
grain yield increase, thus indicating a balance requirement
of soyabean for P nutrition.
Single Superphosphate was superior to all other sources of
phosphorus tested in the trial although the performance of
PAPR-50 was also as good as this commercial fertilizer.
Grain yields obtained at 120 kg P205 ha-
1 application rates of
Sokoto phosphate and Togo phosphate rocks were quite
appreciable. On the over all performance of the various
fertilizers based on their means, SSP > PAPR-50 > SPR > TPR
> control. Statistically significant responses were
obtained up to 120 kg P205 ha-1. The only fertilizer material
that reached its optimum rate of application was the most
soluble P fertilizer (SSP) at the rate of 60 - 120 kg P205 ha"•
The application of these P sources raised the soil
solution P level high enough to benefit the crop. This is
shown by increased Nitrogen and phosphorus contents in
leaves. The total phosphorus concentration in the leaves
were significantly increased (P<0.01) in 1995, with SSP
having the highest value (4.47 g kg"1) at 120 kg P205
application rate.
Data obained from chemical analyses of the soil
receiving the P treatments and cropped, revealed that the
available soil P, ECEC and base saturation were
significantly increased (P<0.05); indicating that the
application of P significantly maintained the soil P and CEC
at optimum level.
The experimental soils had initial low extractable
Bray-1 P, low clay content and extractable bases. A
positive and significant relationship (r=0.281*) was found
between grain yield and Bray-1 P extractable from the soils
at harvest suggesting that plant P uptake and growth could
be limited by amounts of soluble P in the soil.
The influence of the P nutrition on plant performance,
grain yield and the chemical composition of the soil cropped
to soyabean; and particular responses to Sokoto phosphate
rock shows that for direct application, the indigenous SPR
could be as efficient as the other imported phosphates for
soyabean production in this region. These results confirm
previous works which show that although widespread
phosphorus deficiences occur, moderate amounts of phosphate
fertilizers are required to obtain high yields
Description
A Thesis Submitted to the Postgraduate School in Partial
Fulfillment of the Requirements for the Award of the
MASTER of science DEGREE
in the
Department of Soil Science
Faculty of Agriculture
Ahmadu Bello University, Zaria
Nigeria.
OCTOBER, 1997
Keywords
AGRONOMIC,, EVALUATION,, PHOSPHATE,, SOURCES,, SOYABEAN,, PRODUCTION,, NIGERIAN,, SAVANNA,, ALFISOL.