Department of Agronomy, Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, Nainital, Uttar Pradesh
*Present address: C.A.R D.I., University of West Indies, Mana Kingston-5, Jamaica, West Indies.
The balance of soil N and P was estimated in a field experiment consisting of six cropping sequences and three fertilizer constraints for two years on a sandy loam soil. Total N in soil at the end of two years showed a deficit balance of the order of 53 kg N/ha in maize-wheat sequence while other crop sequences, particularly those including legumes, built up the N status of the soil. The highest average gain in soil N was of the order of 81 kg N/ha recorded under maize-potato-green gram sequence. In most of the crop sequences the net gain in soil N was lower with lower dose of fertilizer application. The balance of available soil P in all the rotations was positive and ranged between 1.6 to 14.3 kg P/ha; the highest being under maize potato green gran sequence. Increasing the level of fertilizer application led to greater increase in the available P content of the soil.
Cropping sequences, fertilizer doses, N and P balance sheets
