Balance sheet of nitrogen, phosphorus and potassium under different rice (Oryza sativa-based cropping systems

The field experiment conducted at the Indian Agricultural Research Institute, New Delhi, during the crop years 1995–96 and 1996–97 indicated that rice (Oryza sativa L.)-berseem (Trifolium alexandinum L.) cropping system removed the maximum quantity of NPK (1,140 kg/ha), followed by rice-potato (Solanum tuberosum L.)-greengram (Phaseolus radiatus L.) (1,060 kg/ha) and rice-Indian mustard [Brassica juncea (L.) Czerng. & Cosson]-greengram (1,029 kg/ha) cropping system. Heavy depletion of NPK by rice-berseem cropping system resulted in negative balance of nitrogen (144 kg/ha), phosphorus (23 kg/ha) and potassium (416 kg/ha). Rice-Indian mustard-greengram cropping system also resulted in negative balance of 131 kg/ha of N and 330 kg/ha of K. Nitrogen and phosphorus balance was found positive in rice-wheat (Triticum aestivum L. emend. Fiori & Paol.)-greengram and rice-potato-greengram cropping systems, whereas potassium balance was negative in these cropping systems. These results, thus, show that potassium was found to be most removable nutrient by the crops, which results in mining of soil K and thus calls for adequate K fertilization.