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


09 Jan 2009

2008 Annual Interpretive Summary

Effect of Controlled-Release Urea on Rice Yield and Nitrogen Use Efficiency in the Sichuan Basin, 2008

Improper fertilization is commonly blamed for nutrient losses from farmlands and eutrophication of waterways. One example is the practice of using a single, basal N application in rice. This practice is popular in areas where most of the local labor force choose to temporarily leave farmlands for more industrialized areas in order to earn off-farm income. Three field experiments were conducted on low, medium, and high fertility soils to examine whether controlled-release urea (CRU) can enhance yields and fertilizer use efficiency while still maintaining this single N fertilizer application. Five rates (0, 90, 120, 150, and 180 kg N/ha) of a single basal application of CRU were compared against regular urea (RU), applied at 180 kg N/ha to a medium fertility soil and 120 kg N/ha to a high fertility soil, either as one basal application or as a 40:60 split application applied at planting and as a top-dressing during tillering. All treatments received equal rates of P and K fertilizers.

Results revealed significant differences between basal CRU and RU on the medium and high fertility soils, but not on the low fertility soil. Compared to the basal RU application, rice yields under CRU were 7 to 13% higher on the medium fertility soil and 10 to 16% higher on the high fertility soil. Split application of RU significantly enhanced N use efficiency by 6 to 9%. The CRU treatment produced 3 and 10% higher yield compared to split applied RU on higher and medium fertility soil, respectively. Nitrogen use efficiency of CRU ranged from 42 to 62%. This range was 35% and 29% higher than that measured for basal application of RU on medium fertility soil and high fertility soil, respectively. Application of 90 kg N/ha of CRU produced equivalent, or higher, rice yields than 180 kg N/ha of RU applied basally. These responses are highly economic for farmers and can be considered an environmentally sound solution. More studies will be conducted under different soil conditions to validate the performance of CRU is this first year of trials.

The results suggest that CRU is a promising candidate to replace RU in single, basal N application-based rice crops. Sichuan-BFDP-08