SOIL FERTILITY AS INFLUENCED BY DIFFERENT CROPPING SEQUENCES

An experiment was conducted during 1983-85 to assess the soil fertility, crop production and nutrient removal under different cropping sequences in the presence of recommended doses of nutrients and cultural practices along with 5 tonnes/ha of compost applied to all the crops. At 300% cropping intensity there was an overall increase in organic carbon; and maximum increase in total N (83.9%), available N (69.9%), available P (117.3%) and cation-exchange capacity (37.7%) in the 'Brown Gora' rice (Oryza sativa L.) - Mescavi' berseem (Trifolium alexandrinum L.) - 'Sunaina' greengram (Phaseolus radiatus L.) sequence. It also resulted in a narrow C:N ratio. The available K status of the soil was maximum under the systems in which it was top-dressed during each crop season. The average maximum biomass production in terms of dry-matter yield (25.90 tonnes/ha/year) together with maximum uptake of N (401.4 kg/ha/year), P (95.6 kg/ha/year) and K (348.9 kg/ha/year) were recorded in the 'T 15' deenanath grass (Pennisetum pedicellatum Trin.)-'Mescavi' berseem- 'Ganga Safed 2' maize (Zea mays L.) + 'No. 978' cowpea [Vigna unguiculata (L.) Walp.] sequence.