RESPONSE OF WETLAND RICE TO NITROGEN FROM CATTLE MANURE AND UREA IN ARICE-WHEAT ROTATION

The effect of different rates of N application from cattle manure, ure a, and a combination of manure and urea (1:1) on yield and nutrient up take of wetland rice and soil fertility was studied from 1987 to 1989. The residual effects of cattle manure and urea were assessed on the s ucceeding wheat crop. Cattle manure significantly (P = 0.05) improved rice yield but was less efficient than urea. The combined application of cattle manure and urea showed no positive interaction effects. The mean fertilizer N equivalents of manure ranged from 42 to 52% during t he three years. Total N uptake by rice was also significantly higher f rom urea than manure. Apparent N recovery ranged from 35 to 48% for ur ea and was about 20% for cattle manure. Phosphorus and K uptake by ric e increased in response to N application from urea and cattle manure, but the differences between the two treatments were small. The manure improved Olsen P, and NH4OAc-extractable K contents of the soil. Cattl e manure at 120 and 180 kg N ha(-1) showed significant residual effect s on the yield of the succeeding wheat crop.