Studies On Rice High Yield And High Resource Use Efficiencyunder Different Land Capabilities

In order to produce high grain yield, farmers tend to apply more nitrogen(N) fertilizer than required. Together with improper N application timing, N use efficiency(NUE) is significantly reduced, and a great amount of N is lost to the environment. This leads to a big challenge for human to ensure food safety and reduce agricultural pollution. Rice high yield and high efficiency management practiceis regarded as a poteintial way to simultaneously enhance grain yield and N use efficiency. Field experiments were conducted at Xingfu village located in Suizhou, Hubei Province in 2012-2014 growing seasons of middle rice. A high-yield field and low-yield field were chosen, and there were four treatments in each field, namely the zero-nitrogen control(N0), local farmers’ practice(FP), super high yield management practice(SH), high yield and high efficiency management practice(HH). Grain yield, the aboveground biomass at different growth stages, the SPAD values of flag leaves, NUE, economic return were measured in present study. The main objectives of the study were to:(1) determine the differences in grain yield, NUE and economic return among different management practices, and explore the mechanism underlying the differences;(2) examine whether optimization of management practice could close the yield gap between the two fields, and(3) develop a feasible rice high yield and high efficiency management practice which was easily accepted by farmers. The main results of present study are listed as follows:(1) Compared with FP, grain yield at SH and HH was increased by 4.9% and 5.3%, respectively. Higher grain yield of SH was due to higher biomass, larger number of panicles m-2 and spikelets per panicle. High transplanting density and N fertilizer rate at SH treatment promoted production of more panicles and spikelets m-2. Yield advantage of HH over FP resulted from higher aboveground biomass, HI and larger spikelets number per panicle. There were no significant differences in grain weight and grain filling percentage among FP, SH and HH.(2) N uptake and use efficiency at HH were higher than at FP. Compared with FP, total N uptake, agronomic N efficiency(AEN), recovery efficiency(REN) and partial factor productivity(PFPN) of HH were increased by 13.8, 58.5, 79.9 and 27.3%, respectively. Meanwhile, total N application at HH was 17% less than FP. Total N uptake at SH was 26.1% higher than FP. High N uptake at SH was due to large N fertilizer rate. There was no significantly difference in AEN and PFPN between SH and FP, but higher REN was achieved at SH relative to FP by 75.5%.(3) Through the analysis of economic benefit of different management practices, it was found that economic input was higher at SH and HH than at FP by 1920 and 613 yuan per hectare, respectively. HH achieved larger net economic return than FP by 916 yuan ha-1, and the increase was higher at the high-yield field. In contrast, net ecnomic return was lower at SH than at FP by 903 yuan ha-1. The high input of SH was the main factor causing poor net economic return.(4) Grain yield at N0 treatment in high-yield field was higher than in low-yield field, and the differences were 0.56-0.91 t ha-1. Soil fertility accounted for the yield variation at N0 between the two fields. Adoption of FP, SH and HH could reduce the difference in grain yield between high-yield field and low-yield field, which indicated that it is feasible to improve grain yield at low-yield field to the level athigh-yield field through adopting appropriate management practices.In conclusion, compared with FP, higher yield, NUE and net economic return were significantly improved at HH. As only one extra N fertilizer application at PI was added at HH relative to FP, HH in present study was relatively simple and easy for farmers to masterin a short time compared with the ones reported previously. This indicated that HH is possessed of popularization and application value. Higher grain yield of HH at high-yield field than at low-yield field indicated that HH should be optimized according to soil fertility. Furthermore, HH in present study could integrates with appropriate methods for seedling raising, optimal transplanting density, and etc., so it could be more suitable for mechanized rice farming in the future.