Effect of release controlled urea on rice yield and N use efficiency in Sichuan basin


04 Jan 2012

2011 Annual Interpretive Summary

Response of Winter Rapeseed to Controlled-Release Urea in Sichuan, 2011

The objective of this field experiment was to evaluate the response of winter rapeseed to controlled-release urea (CRU) under rain-fed conditions in Sichuan Basin. The deliverables from the project will be the impact on crop yield, N uptake, and economic benefit. The field experiment in 2011 was conducted on an alluvial loam soil with four N rates (0, 90, 135, and 180 kg N/ha) and three replications. Each rate of N was tested as paired CRU and regular urea (RU) treatments for strict comparison of CRU effect. Two split application treatments were included, one with 40% RU basal at transplanting and 60% RU top dress one-month after transplanting, and the second split used 40% RU and 60% CRU both applied at transplanting. All treatments received equal rates of P and K fertilizers that were used as basal application.

Results showed that at the same N rate, the RU treatment always produced much higher or significantly higher rapeseed yield than the CRU treatments. The RU 40%+CRU 60% applied as basal application achieved the highest seed yield among all the treatments. Rapeseed yield increased with an increase in N rate and leveled off when N rate was above 135 kg/ha for RU, but with no yield drop for CRU. This implies that under conditions without irrigation, a dry growing season (accumulative precipitation of 110 mm, but unevenly distributed in 7 months) severely restricted N release from the CRU and thus, rapeseed growth. As a result, CRU could not supply sufficient N to rapeseed no matter what N rates there were in dry season. Accordingly, all the RU treatments had higher N recovery by 4 to 10% and agronomic efficiency by 1 to 2 kg seed/kg N compared with its counterpart CRU treatments. The result further suggested that though CRU is an excellent N fertilizer in wet or irrigation conditions, caution should be taken when it is used under dry season with no irrigation. Sichuan-BFDP-08