Abstract:

The annual total amount of crop residue straw exceeds billion tons in China. However, about 45%–60 % of them are burnt or discarded, which not only wastes organic fertilizer source, but also pollutes the environment. Meanwhile, heavy use of nitrogen fertilizer has become a serious problem in rice production in this country. The purposes of this study were to investigate the effects of wheat straw incorporation to soil and site-specific nitrogen management (SSNM) on the growth and grain yield of rice. Two mid-season japonica rice cultivars, Wuxiangjing 14 and Yangjing 9538, were field-grown with three nitrogen (N) fertilizer treatments, no nitrogen application, farmers’ fertilizer-N practice (FFP), and SSNM base on chlorophyll measurement meter (SPAD) readings. The results showed that, compared with FFP, SSNM reduced N application by 40.0%–41.7% and increased grain yield by 3.81%, on average. The grain yield in the wheat residue-incorporated treatment was 2.49%, on average, higher than that in the residue-removed treatment. The agronomic efficiency, recovery efficiency and physiological efficiency of nitrogen fertilizer under wheat residue incorporation were higher than those under the residue-removed. In comparison with those under the residue removal and FFP, the number of stems and tillers, leaf area index, and biomass accumulation were less or lower under the residue incorporation and SSNM during the early growth period, but the differences were reduced at heading and thereafter. Both the residue incorporation and SSNM increased the percentage of productive tillers, photosynthetic rate of flag leaves and root activities during grain filling. The results suggest that both the residue incorporation and SSNM benefit the photosynthetic production of rice during the later growth period and an increase in the production efficiency. Wheat residue incorporation and SSNM increased nitrogen harvest index and agronomic efficiency, recovery efficiency, physiological efficiency, and partial factor productivity. Reasons for the characteristics of the grain yield, growth and development and nitrogen fertilizer use efficiency under the residue incorporation and SSNM were discussed.

Key words: Rice, Wheat residue incorporation, Farmers’ fertilizer-N practice, Site-specific nitrogen management, Grain yield, Growth and development characteristics, Nitrogen fertilizer use efficiency