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 The objective of this research, carried
out by Dr. Upendra Singh and Dr. S. H. (Norman) Chien, is to conduct
strategic and adaptive research on alternative P fertilizer sources and
factors affecting their effectiveness in various cropping systems. A
suite of greenhouse experiments in conjunction with a field trial in
Davié, Togo was conducted to improve our understanding of PR residual
effect on different cropping systems. The field trial is on maize-maize
cropping. In the greenhouse the effect of PR and TSP application on
various cropping systems and the impact of these cropping systems on PR
availability and residual effect were quantified. The cropping systems
included ryegrass – wheat, canola – wheat, wheat – wheat, cowpea –
wheat, mucuna (5 different cultivars) – wheat, and rice – wheat. The PR
response and effectiveness was dependent on the crops. The residual data
are being analyzed. The results will be used to test the
residual/long-term component of the PRDSS.
A new study was launched by a doctoral
student from the University of Sao Paulo to investigate the effect of
calcination on increasing the agronomic effectiveness of phosphate rock
deposits containing iron/aluminum minerals (crandallites). The study
includes: (1) effect of temperature profile on solubility, (2)
equilibrium solubility of calcined samples, (3) kinetic dissolution of
calcined samples as influenced by soil pH and water regime, and (4)
agronomic evaluation of calcined samples for upland rice and flooded
rice.
Work continues to investigate whether
two commonly used soil tests (Olsen and resin) can underestimate
soil-available phosphorus in calcareous soils containing gypsum, which
are widely distributed in the Middle East. The result might lead to
over-recommending phosphorus fertilizer application and adding
unnecessary inputs to the farms. The IFDC-developed Pi test (iron-oxide
impregnated filter strip) may prove to be effective for these types of
soils. An on-going greenhouse experiment with wheat is being used to
test the hypothesis.
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