Abstract
The effect of different rates of N application from cattle manure, urea, and a combination of manure and urea (1: 1) on yield and nutrient uptake of wetland rice and soil fertility was studied from 1987 to 1989. The residual effects of cattle manure and urea were assessed on the succeeding 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 the three years. Total N uptake by rice was also significantly higher from urea than manure. Apparent N recovery ranged from 35 to 48% for urea and was about 20% for cattle manure. Phosphorus and K uptake by rice increased in response to N application from urea and cattle manure, but the differences between the two treatments were small. The manure improved organic C, Olsen P, and NH4OAc-extractable K contents of the soil. Cattle manure at 120 and 180 kg N ha-1 showed significant residual effects on the yield of the succeeding wheat crop.
