Dilemma of using DAP vs other phosphatic fertilizers illusion or reality.
1996
Khattak R.A. | Khan M.J.
Nitrogen and phosphorus being major essential plant nutrients are limiting crop yield because of low organic matter content of our soils and due to high pH and excessive CaCO3 in plain and nearly plain cultivated areas. The supplemental use of these nutrients through fertilizers is thus mandatory for profitable and potential yield of crop/plant on sustainable bases. Diammonium phosphate (DAP) is one of the major phosphatic fertilizers imported to meet the P and N requirements of crops. However, there is a growing concern among the farmer and agronomist regarding its effect on raising the soil pH to level where by ammonia, which is toxic to plant seedlings, is produced under alkaline soil environment. It is well documented that monoammonium phosphate (MAP) produces low initial pH (3.5), acidifies the soil and enhance micronutrient and soil P solubility but only on short term basis and in small volume of soil while in the long term it is believed that DAP also lower the pH of bulk soil through nitrification. In this paper, an effort has been made to present the theoretical basis and concepts which will help in resolving the dilemma of using DAP, urea and MAP. The effect of these fertilizers on soil pH, nutrients solubility and ammonia production have been critically analyzed. It is felt that further research is needed to evaluate the degree and extent to which these fertilizers can influence soil and plant under field conditions.
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