Effects Of Straw Mulching On Soil Properties And Yield Of Double Cropping Late-Season Rice (Oryza Sativa L.)

The gross amount of crop residue reached 6.73×10⁸ t in China, among which the amount of rice straw account for 23.6%. Recently, with the development of agriculture, chemical fertilizer was widely applied, but the quantity of barnyard manure and green manure decreased greatly. Straw is an important organic fertilizer source of paddy soil. However, 45%—60% of crop straw were burnt or discarded, which not only wasted organic fertilizer source, but also polluted the environment. Straw returning play a significant role in alleviating the shortage of organic fertilizer input, strengthening nutrient recycle and increasing soil fertility and crop yield. Popularizing straw returning is an important measure for developing ecological agriculture and sustainable development of Chinese agriculture. It is an effective way for saving organic fertilizer source and improving the environment. Two field experiments were conducted at Baiyun experimental station, Guangdong Academy of Agricultural science, Guangzhou, China.Tianyou998, a hybrid rice, was arranged in split plot design experiments with four replicates with straw mulching as main factor and four N rates as split factor. Soil properties Grain yield, yield components, dry matter accumulation, LAI, N uptake and fertilizer-N use efficiency were measured. Effects of factors on grain yield and reasons for yield increasing were studied. The results were as follows:1. Some physical and chemical properties of soil were improved by straw mulching. Soil organic matter was significantly increased. Porosity and NH₄-N content of soil were increased. Soil bulk density was decreased by straw mulching.2. Agronomic efficiency (AE), partial factor production of applied N (PFP) and nitrogen recovery efficiency (RE) were increased by straw mulching. However, nitrogen physiology efficiency (PE) was decreased.3. Grain yield was increased by straw mulching under different N rates. Path analysis showed that Panicles (no. /m²) had the biggest direct effect to the yield. The reason was that maximum tiller number (no. /m²) and productive tiller rate (%) were both increased by straw mulching. Dry matter accumulation at MA period was significantly and positively correlated with grain yield (r=0.862**). The reason was that straw mulching improved LAI and SPAD value at different periods. LAI, SPAD value at PI and HD periods were significantly and positive correlated with grain yield. So LAI, SPAD value at PI and HD period were important factors affecting grain yield.4. Grain yield was not affected significantly by three N rates(N1,N2 and N3). It was not necessary to apply fertilizer-N before MT period.