[Differences in uptake, utilization and loss of nitrogen and phosphorus in a Chinese double rice cropping system under different irrigation and fertilization managements].

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 T(no chemical fertilization with traditional flooding irrigation), T(common chemical fertilizer of 273 kg N·hm, 59 kg P·hm, and 112 kg K·hm combined with traditional flooding irrigation), T(chemical fertilizer of 240 kg N·hm, 52 kg P·hm, and 198 kg K·hm combined with traditional flooding irrigation) and T(chemical fertilizer combined with shallow intermittent irrigation) treatments. Results showed that early rice grain yield in the T, T and T 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 T treatment, respectively. The T, T and T treatments significantly increased the uptake of N and P in aboveground parts of the plants, especially in grains. The T, T and T 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 T, respectively. Furthermore, T 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 T decreased total dissolved N (DN) by 16.0% in comparison with T. Dissolved inorganic N loss in surface runoff occurred mainly in the form of NO-N (nitrate N) under different water and fertilizer regimes. However, there were no significant differences in AEN and AEP between T and T treatments. These findings suggested that optimal applications of water and fertilizers (T) might increase N and P uptake in rice plants, maintain yield, and reduce N loss, especially in the form of NO-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.