[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 ₀ (no chemical fertilization with traditional flooding irrigation), T ₁ (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), T ₂ (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 T ₃ (chemical fertilizer combined with shallow intermittent irrigation) treatments. Results showed that early rice grain yield in the T ₁ , T ₂ and T ₃ 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 ₀ treatment, respectively. The T ₁ , T ₂ and T ₃ treatments significantly increased the uptake of N and P in aboveground parts of the plants, especially in grains. The T ₁ , T ₂ and T ₃ 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 ₀ , respectively. Furthermore, T ₃ 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 ₃ decreased total dissolved N (DN) by 16.0% in comparison with T ₁ . Dissolved inorganic N loss in surface runoff occurred mainly in the form of NO ₃ ^- -N (nitrate N) under different water and fertilizer regimes. However, there were no significant differences in AEN and AEP between T ₂ and T ₃ treatments. These findings suggested that optimal applications of water and fertilizers (T ₃ ) might increase N and P uptake in rice plants, maintain yield, and reduce N loss, especially in the form of NO ₃ ^- -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.