Summary Significantly lower amounts of exchangeable NH4, soluble NO3 and clay-fixed NH~ forms of N were observed in the unfertilized fields with high rather than low-density cropped plots. Irrespective of planting densitites, the fixed NH4 content in soil increased with increase in the period of crop growth. N uptake by plant and total bacterial population ofrhizosphere soil were significantly higher in the plots with the high than with the low-density planting. Availability of native fixed NH~ § to crops and biological utilization of a considerable amount of recently mineralized NH4 § in fixed form is indicated.

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