Abstract
Straw-derived N (Straw-N) is an important organic N source, but its distribution in soil–rice systems regulated by water management and N fertilization is poorly understood. Therefore, a pot experiment using 15N-labeled wheat residue was conducted with conventional flooded irrigation (CF) and alternate wetting/drying irrigation (AWD) both with and without N fertilization. Results showed that the whole-plant straw–N recovery rate and the soil residue rate were 9.2–11.9% and 33.5–43.1%, and 10.2–13.8% and 33.7–70.2% at panicle initiation stage (PI) and mature stage (MS), respectively. There was no interaction between water management and N fertilization. Compared to CF, AWD did not affect whole-plant straw-N absorption and significantly changed its distribution in various plant parts, such as increasing the straw-N accumulation in roots at PI and decreasing it at MS. N fertilization addition markedly promoted the transfer of straw-N to the plant but reduced the contribution rate of N uptake by the plant. Furthermore, AWD or N fertilization addition allowed more straw-N to remain in the soil, and a positive interaction effect on the straw-N loss mitigation was found. These results suggest that AWD combined with N fertilization addition is a great measure to improve the efficient utilization of straw-N and avoid the risk of environmental pollution in a soil–rice system.
Highlights
Rice is a vital staple food, feeding over 50% of the global population [1]
The straw-derived nitrogen (straw-N) amount in the undecomposed straw declined markedly before panicle initiation stage (PI) and slowed down; 44.10–66.47 mg pot−1 and 20.04–40.77 mg pot−1 at PI and mature stage (MS)
Our results showed that alternate wetting/drying irrigation (AWD) gave a similar straw-N absorption in the whole plant but markedly changed the straw-N allocation in various plant parts compared to conventional flooded irrigation (CF)
Summary
Rice is a vital staple food, feeding over 50% of the global population [1]. China is the world’s largest rice–producing country, accounting for 27.4% of global rice production [2], and China’s rice cropping systems play an important role in satisfying global food demand. The rice–wheat system is the most popular cropping system in China, with an area of 13 million hectares and an average straw production of 4 t ha−1 [3,4]. Straw incorporation is widely regarded as a great management practice to improve soil fertility and increase rice production [4,5,6], providing abundant straw-derived nitrogen (straw-N). The annual total amount of straw-N in China is 5.5 × 106 t for rice and 5.4 × 106 t for wheat [11]. To enhance the efficient utilization of straw nutrients, it is necessary to better understand the distribution of straw-N and its contribution to a soil–rice system, especially in rice–wheat systems
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