The research progress and prospects of high yield and high efficiency nitrogen application for hybrid rice

ObjectivesAlong with the breakthrough in hybrid rice breeding, the development in the high yield and high efficiency cultivation techniques has given full play to the potential of hybrid rice varieties. In this study, research progress of the nitrogen (N) absorption and utilization characteristics, as well as the high yield and high efficiency N application techniques was summarized, which could promote the popularization and application of hybrid variety in rice production.

Main advancesThe N absorption of 100 kg seeds of hybrid rice is from 1.4 to 2.0 kg, which is generally lower than that of inbred rice. However, due to the high biomass and yield potential, the N requirement per unit area of hybrid rice is still higher than inbred rice. Unlike inbred rice, hybrid rice possesses higher N use efficiency, such as N recovery efficiency of high yield hybrid rice with precise and quantitative N application has reached to 40%–45%. Compared to the early three-line hybrid rice varieties, both biomass and N absorption capacity are improved while N use efficiency is stabilized by the two-line hybrid rice and super hybrid rice varieties, which has contributed to the high production of rice by establishing a better nutrition foundation. Hybrid rice, compared to inbred rice, has more chlorophyll content, leading to deeper green of the leaf lamina. Based on the close relationship between the leaf color and N metabolism in the leaf lamina, a lot of N diagnostic methods, such as the method of SPAD, spectral monitoring, and leaf color difference were founded. New and high efficiency fertilizers (e.g. slow/controlled release fertilizer, polyaspartic acid urea, and fertilizer with nitrification inhibitor) were used to enhance both yield and N use efficiency of hybrid rice. N management methods based on the real-time and site-specific N managements and postponing N application theories were established, in which precise and quantitative N application, N application of ‘San-ding’ cultivation, and regular nitrogen application were better adapt to large area production. Moreover, the combined use technique of N fertilizer and other fertilizers was developed.

ProspectivesHigh N efficiency management techniques focus on reducing N amount and improving N use efficiency, as well as the mechanization of N application are the core of the future research. Meanwhile, method specific to variety and new fertilizer is a development direction for the high yield and high N use efficiency application technique for hybrid rice.