Effects of the amount of basic and tillering nitrogen on population quality and nitrogen utilization of machine-transplanted rice in rice-duck farming system

Wujing15 (japonica rice cultivar) was used, and four different amount of basal and tillering nitrogen fertilizer (BN) were conducted to investigate the effects of nitrogen fertilizer on the population quality and nitrogen utilization of machine-transplanted rice in rice-duck farming system. The results showed as followed: 1) In rice-duck farming system, along with the reduction of the amount of BN, the maximum number of tillers and the speed of tiller appearance and dying decreased; the proportion of effective leaf area, high effective leaf area and the ratio of spikelets number to leaf area increased; dry matter and nitrogen accumulated from heading to maturity decreased; nitrogen uptake decreased at each stage especially from jointing to heading. 2) when the amount of BN at a suitable level, and the ratio of BN to topdressing nitrogen was 4.5: 5.5 the ratio of panicle number to maximum number of tillers was higher under the machine-transplanted rice-duck farming system which at the same time contained a suitable LAI and reached the highest amount of day matter accumulated from heading to maturity. Moreover, higher BN utilization efficiency before jointing stage, nitrogen utilization efficiency, nitrogen harvest index, nitrogen agricultural efficiency and nitrogen partial factor productivity were achieved at that point also. 3) machine-transplanted rice-duck farming system not only enhanced the nitrogen fertilizer use efficiency before jointing and of the whole planting season, but also improved the population quality and thus strengthen the ability of day matter producing and eventually rice yield.