Differences in dry matter accumulation and nitrogen absorption and utilization among early, late and middle rice

Objectives The pattern of dry matter accumulation, N absorption and utilization of early, late and middle rice were summarized, to provide a theoretical basis for scientific application of nitrogen fertilizer.

Methods We collected data from China National Knowledge Infrastructure Database and China Science and Technology Journal Database. The searched key words included year 2000—2016, field experiment, indica rice, optimum fertilizer treatment for best target yield, etc. We analyzed the yield, N accumulation and uptake for 100 kg grain production in early, late and middle rice. Based on above results, field trials were carried out in Dajin Town, Wuxue City, Hubei Province, in 2016 and 2017. The dry matter weight and N content in the key growth period of rice were determined, and the N accumulation was calculated. The logistic equation y = K/ (1 + ae^–bt) was used to fit the dry matter and N accumulation process of rice, to studied the dry matter accumulation and N absorption and utilization of early, late and middle rice.

Results  The qualified sample number for early, late and middle rice were 92, 116 and 132; for N accumulation were 55, 56 and 55; for N uptake per 100 kg grain were 50, 48 and 54. The experiments covered provinces of Hubei, Hunan, Jiangxi, Guangxi, Jiangsu, Anhui, Zhejiang, Fujian and Sichuan. From the published literature the average yields of early, late and middle rice were 7.40, 7.84 and 8.67 t/hm², respectively; the average N accumulation were 140.8, 148.9 and 157.7 kg/hm²; the N uptake for 100 kg grains were 2.00, 1.92 and 1.79 kg, respectively. Our field trial results showed that the dry matter accumulation of early, late and middle rice were in line with the growth trend of “slow–fast–slow”, and the rapid accumulation period of dry matter were 28–54 days, 24–54 days and 30–63 days after transplanting, all in jointing–filling stage. The duration of dry matter accumulation were 26 days, 30 days and 32 days, respectively, and in order of middle rice > late rice > early rice. The N accumulation of early, late and middle rice all showed a trend of “slow–fast–slow”. The rapid N accumulation period were 17–41 days, 14–46 days and 11–43 days after transplanting. Duration of N accumulation were 24 days, 33 days and 32 days, respectively. The rapid accumulation of N in middle and late rice were longer than that in early rice. The N use efficiency for grain output of early, late and middle rice were 50.5–54.4 kg/kg, 54.6–57.9 kg/kg and 62.7–64.8 kg/kg, and that of middle rice was significantly higher than early and late rice. The N partial productivity were 41.4–47.8 kg/kg, 56.1–58.8 kg/kg, 61.8–62.1 kg/kg, that of middle rice was significantly higher than early rice.

Conclusions The dry matter and nitrogen accumulation process of early, late and middle rice are accordant and all in “S” shape, however, the intensity of dry matter and nitrogen accumulation are different. The duration of rapid accumulation of dry matter and nitrogen accumulation in middle and late rice are longer than that of early rice, so they can absorb more nutrients and accumulate more dry matter. And the yield level and nitrogen uptake are in order of middle rice > late rice > early rice, indicating that middle rice need more nitrogen input than early rice and late rice.