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Increased hill density can compensate for yield loss from reduced nitrogen input in machine-transplanted double-cropped rice

Huang, Min, Chen, Jiana, Cao, Fangbo, Zou, Yingbin
Field crops research 2018 v.221 pp. 333-338
biomass production, field experimentation, grain yield, hills, inflorescences, labor, leaf area index, nitrogen, nitrogen fertilizers, planting, rice, China
Reducing external inputs, including labor and N fertilizer, is critical to sustainable double-cropped rice production in China. Dense planting is a recommended strategy to reduce N rate in rice production, and this strategy may be more practical for machine-transplanted rice as machine transplanting can achieve high hill density with less labor. However, little work has been done to demonstrate the feasibility of such a strategy in machine-transplanted double-cropped rice. This study was conducted to determine the effects of reduced N rate and increased hill density on yield attributes and grain yield in machine-transplanted double-cropped rice. Field experiments were done in two years with three treatments: (1) high N rate with low hill density (HNLD), (2) low N rate with low hill density (LNLD), and (3) low N rate with high hill density (LNHD).Results showed that LNLD had 19% and 16% less panicle number per unit land area, 27% and 26% smaller leaf area index, 18% and 14% lower biomass production, and consequently 13% and 11% lower grain yield than did HNLD in early and late season, respectively. In contrast, these yield attributes and grain yield were generally equal or higher under LNHD than under HNLD. Our study indicates that the potential negative effects of reduced N rate on yield attributes and grain yield can be compensated for by increased hill density, and suggests that dense planting is a feasible strategy to reduce N input in machine-transplanted double-cropped rice.