Abstract
To compare N uptake and use efficiency of rice among different environments and quantify the contributions of indigenous soil and applied N to N uptake and use efficiency, field experiments were conducted in five sites in five provinces of China in 2012 and 2013. Four cultivars were grown under three N treatments in each site. Average total N uptake was 10–12 g m−2 in Huaiji, Binyang, and Haikou, 20 g m−2 in Changsha, and 23 g m−2 in Xingyi. Rice crops took up 54.6–61.7% of total plant N from soil in Huaiji, Binyang, and Haikou, 64.3% in Changsha, and 63.5% in Xingyi. Partial factor productivity of applied N and recovery efficiency of applied N in Changsha were higher than in Huaiji, Binyang, and Haikou, but were lower than in Xingyi. Physiological efficiency of soil N and fertilizer N were lower in Changsha than in Huaiji, Binyang, and Haikou, while the difference in them between Changsha and Xingyi were small or inconsistent. Average grain yields were 6.5–7.5 t ha−1 (medium yield) in Huaiji, Binyang, and Haikou, 9.0 t ha−1 (high yield) in Changsha, and 12.0 t ha−1 (super high yield) in Xingyi. Our results suggest that both indigenous soil and applied N were key factors for improving rice yield from medium to high level, while a further improvement to super high yield indigenous soil N was more important than fertilizer N, and a simultaneous increasing grain yield and N use efficiency can be achieved using SPAD-based practice in rice production.
Highlights
Nitrogen (N) is usually the nutrient limiting rice production and current high yields of irrigated rice were associated with large applications of fertilizer N (Cassman et al, 1998)
It is projected that a rice yield increase of more than 1.2% per year will be required in the decade (Normile, 2008)
The N uptake from fertilizer N was significantly higher in Changsha than in Huaiji, Binyang, and Haikou by 27.1–57.2%, while there was no significant difference in N uptake from fertilizer N between Xingyi and Changsha, execpt N uptake of treatment N2 in Xingyi in 2012
Summary
Nitrogen (N) is usually the nutrient limiting rice production and current high yields of irrigated rice were associated with large applications of fertilizer N (Cassman et al, 1998). The high grain yields of rice in Taoyuan and Yanco were associated with high N uptake, the accumulation of N more than 250 kg ha−1 is required to achieve these yield levels (Horie, 1997; Ying, 1998b). These previous studies on the N uptake requirements at these yield levels were usually conducted by comparing a high-yielding site with a check site, or using only one cultivar. The objectives of this study were to (1) compare the characteristics of N uptake and NUE of rice among different environments and (2) quantify the contribution of soil indigenous and applied N uptake and use efficiency over a wide range of environments
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