RESUMO
In order to optimize water and fertilizer use in the double-cropping rice in eastern Fujian Province, a field runoff plot experiment was conducted to investigate rice yield, nutrient uptake, and runoff losses of N (nitrogen) and P (phosphorus) in the T0(no chemical fertilization with traditional flooding irrigation), T1(common chemical fertilizer of 273 kg N·hm-2, 59 kg P·hm-2, and 112 kg K·hm-2 combined with traditional flooding irrigation), T2(chemical fertilizer of 240 kg N·hm-2, 52 kg P·hm-2, and 198 kg K·hm-2 combined with traditional flooding irrigation) and T3(chemical fertilizer combined with shallow intermittent irrigation) treatments. Results showed that early rice grain yield in the T1, T2 and T3 treatments significantly increased by 0.7, 1.0, 1.1 times, late rice grain yield significantly increased by 0.9, 1.1, 1.0 times compared to that in the T0 treatment, respectively. The T1, T2 and T3 treatments significantly increased the uptake of N and P in aboveground parts of the plants, especially in grains. The T1, T2 and T3 treatments significantly increased N uptake by 1.1, 1.2, 1.2 times, increased P uptake by 0.9, 1.4, 1.6 times in early-season grains, and significantly increased N uptake by 0.8, 1.0, 1.0 times, increased P uptake by 0.7, 0.9, 0.9 times in late-season grains, compared to T0, respectively. Furthermore, T3 increased agronomic N use efficiency (AEN) and agronomic P use efficiency (AEP) by 71.1% and 69.2% in early rice plants, increased AEN and AEP by 26.4% and 25.0% in late rice plants, whereas T3 decreased total dissolved N (DN) by 16.0% in comparison with T1. Dissolved inorganic N loss in surface runoff occurred mainly in the form of NO3--N (nitrate N) under different water and fertilizer regimes. However, there were no significant differences in AEN and AEP between T2 and T3 treatments. These findings suggested that optimal applications of water and fertilizers (T3) might increase N and P uptake in rice plants, maintain yield, and reduce N loss, especially in the form of NO3--N in surface water from early rice field. In general, this study could provide theoretical support for the optimization of irrigation and fertilization and for the control of N and P non-point source pollution from the double cropping rice paddy fields in eastern Fujian Province.
