Precise Postponing Nitrogen Application and Its Mechanism in Rice

Abstract

Leaf ages of nitrogen application for high yield and apparent nitrogen recovery efficiency were specified through applying nitrogen fertilizer once in middle stage of growth and development using early-maturing and late japonica rice-Wuyunjing 7, Wuxiangjing 14, Changyou 1 as materials. Based on this, we studied precise postponing nitrogen application and its mechanism. Results showed that leaf ages of nitrogen application to high yield and apparent nitrogen recovery efficiency were 3rd leaf and fourth leaf from the top in early-maturing and late japonica rice. Using nitrogen in 3rd and 4th leaf from the top, made more panicles and spikelets per panicle, larger total spikelets and stable filled-grain percentage and 1000-grain weight, and lower max number of stems and tillers, higher ratio of productive tillers to total tillers, higher nitrogen accumulation, max LAI, LAD and dry matter weight in population growth and development. Yield with "PPM" (precise promoting in the middle phase) of nitrogen was significantly more than that of CK. Compared to CK, there were more significantly apparent nitrogen recovery efficiency, physiological nitrogen use efficiency, agronomic nitrogen use efficiency and yield of ear nitrogen, but lower nitrogen requirement for 100 kg grain in "PPM" of nitrogen. Mechanism of high yield and apparent nitrogen recovery efficiency in "PPM" of nitrogne was that high ratio of productive tillers to total tillers and enough population panicles were formed through consolidating population panicles and controlling non productive tillering and low effective tillering; high grain-leaf ratio (filled grains per cm2 leaf area, grain weight per cm2 leaf area), enough quantity and good quality of dry matter in heading were obtained through forming large population spikeletes, high and appropriate LAI and fine canopy structure; intense source and smooth translocation, effective sink-filling ability were enlarged through enriching dry matter accumulation after heading and coordinating producton and translocation of dry matter from population stems and sheaths.