Grain Yield And Nitrogen Use Efficiency Under Different Crop Management Practices In Single Season Rice

Burgeoning population and increasing rice demand in China necessitate higher yields. To ensure high rice yield, nitrogen is one of the nutrients often applied in excess, which in turns lead to lodging, insect and disease damage, environmental pollution, and lower nitrogen use efficiency. Development and optimization of crop management technology is important for increasing both rice yield and nitrogen use efficiency.Present research was conducted in2012and2013growing seasons at Zhougan and Zhangbang villages located in Wuxue, Hubei Province, to evaluate the response of rice yield and nitrogen use efficiency to different crop management treatments (zero-N, NO; farmers’ practice, FP; optimized farmers’ practice, OPT1; super high yield cultivation, SHY; optimized super high yield cultivation, OPT2and high frequency fertilization, HFF).Comparing to FP, the seedling raising method of OPT1treatment was changed from’ paddy-raised to dryland-raised, transplanting density was increased and the posting nitrogen application practice was introduced. SHY treatment was applied organic manure, further increased transplanting density, and introduced site-specific nitrogen management. OPT2treatment was reduced transplanting density and fertilizer inputting rate, comparing to SHY. HFF treatment had a same transplanting density as OPT2treatment, while divided total nitrogen and potassium fertilizer into10parts and inputted every7days.The main objectives of this study were,(1) to compare yield variations in different cultivation patterns, and to explore the mechanism of higher yield formation in optimized crop managements,(2) to assess the nitrogen use efficiency of rice under different crop managements, and (3) to ascertain the response of rice yield and its related attributes to different sites under different cultivation patterns. Results depicted that,1. Comparing to FP, OPT1, SHY, OPT2and HFF treatment have increased rice yield by 5.7,7.1,2.8and9.0%, respectively. Panicle number per m2of OPTl, SHY, OPT2and HFF treatment have increased by10.5%,25.7%,21.5%and20.2%comparing to FP, which is response to the yield difference between optimized crop management treatments (OPTl, SHY, OPT2, HFF) and FP. SHY and HFF treatments didn’t show a stable and significant yield advantage comparing to OPTl. Neither resource nor labor input leads to a further yield increase.2. Seedling raising methods, transplanting density, nitrogen application timing and proportion were all optimized in OPTl treatment comparing to FP. OPTl treatment could mitigate the contra-diction between panicle number per m2and spikelet number panicle, when increasing panicle number per m2. Meanwhile, suitable LAI during ripe stage of OPTl could make sure a large amount of biomass accumulation. Comparing to FP treatment, OPTl has increased nitrogen recovery efficiency by28.0percentage points by decreasing nitrogen input of30kg ha-1. With increasing yield and nitrogen use efficiency and decreasing nitrogen rate, OPTl has accomplished a rice production with both "high yield and high resource use efficiency".3. Soil fertility of Zhougan is much higher than Zhangbang, which leads to a yield advantage of0.531ha-1of NO treatment in Zhougan. Comparing to NO treatment, nitrogen input has increased rice yield by1.841ha-1and1.561ha-1in Zhougan and Zhangbang, respectively. Comparing to FP treatment, optimized crop management treatments have increased rice yield by0.711ha-1in Zhougan and by0.531ha-1in Zhangbang, respectively. Optimized crop management treatments have had a better performance in higher soil fertility conditions.4. The number of differentiated secondary branches per panicle in Zhougan were23%higher than that in Zhangbang, which might be responsible for site variations in spikelet number per panicle and sink size, which ultimately lead to yield difference of0.961ha-1between Zhougan and Zhangbang. In addition, dry matter accumulation after panicle initiation in Zhougan and Zhangbang was1043.3g m-2-and872.4g m-2, respectively. Higher dry matter accumulation during reproductive stage in Zhougan, may also pose such variations. In conclusion, comparing to FP, optimized crop managements has increased rice grain yield and nitrogen use efficiency, while neither resource nor labor input increasing lead to a further yield increase. Among four optimized crop managements, OPTl has accomplished a rice production with both "high yield and high resource use efficiency". Optimized crop management treatments have had a better performance in higher soil fertility conditions.