Effects of the blending ratio of controlled release nitrogen fertilizer and urea on soil nitrogen supply in the mid-late growing stage and yield of wheat and rice

ObjectivesEfficient use of controlled-release nitrogen fertilizer (CRNF) and urea (UR) will improve crop growth and save the costs for the fertilization practice at the same time. So the optimum ratio of CRNF and UR was studied in wheat and rice production for high yield and profit.

MethodsOne-year field experiment was conducted in rice and wheat rotation system. Under the total N input of 150 km/hm², the addition ratio of CRNF of 0, 10%, 20%, 40%, 80%, 100% was set up for both the crops, which were recorded as T1, T2, T3, T4, T5 and T6, respectively. Except urea control, the N in treatments was all completely basal applied. The NH₄⁺-N, NO₃^--N contents of soil, plant height, biomass, yield component factors and economic benefits were calculated

Results1) In all the CRNF addition treatments, the soil inorganic nitrogen content in the mid-late stage of rice and wheat was increased significantly, with the highest increase in treatment T4 (40% CRNF). 2) When the CRNF addition was more than 20%, the rice biomass and yield were all increased significantly, compared to T1 (no CRNF addition),and the highest biomass and yield were obtained in T4 treatment, in which the rice yield was increased by 11% and wheat yield by 14% respectively. Among the yield components, the wheat spike length was elongated by 19.19%, and the grain number per panicle was increased by 13.79% and the 1000-grain weight by 8.43% respectively. 3) With the increasing of CRNF ratio, the economic benefits in both rice and wheat increased at beginning and then decreased afterwards, with the peak in T4. With T4 treatment, the income for wheat was 1108.12 yuan/hm²(increased by 23.24%) and for rice was 2497.80 yuan/hm²(increased by 14.87%), compared with T1.

ConclusionAppropriate blending of commercial urea and controlled-release urea will enhance the nitrogen supply of soil in the mid-late growing stage of rice and wheat, thus increase the yield effectively and the benefit directly. The suitable blending ratio of two kinds of nitrogen fertilizer is 40% CRNF with 60% conventional UR in the tested region.