Effects of waterlogging at anthesis stage on nitrogen content of different forms in soil and nitrogen accumulation and translocation of wheat and yield

【Objective】To discuss effects of waterlogging at anthesis stage on content of nitrogen of different forms in soil and its relationship with wheat grain yield and nitrogen accumulation in plants, so as to provide theoretical basis for waterlogging-resistant cultivation of wheat in Jianghan Plain.【Method】Field split-plot test was carried out. Xiangmai 55 and Zhengmai 9023 were taken as test materials, the treatments of no waterlogging(CK) and continuous waterlogging during the anthesis stage for 7 d(WL) were set, and content of nitrogen of different forms in soil, nitrogen accumulation and transportation of wheat plants, yield, yield structure and other indicators were determined, and the relationship between the changes of content of nitrogen of different forms in soil and grain yield as well as plant nitrogen accumulation were analyzed.【Result】The response intensity of nitrogen content of various forms in 0-20 cm soil layer to waterlogging was more severe than that in 20-40 cm and 40-60 cm. Compared with the CK, under the WL treatment(0-7 d after waterlogging), the nitrate nitrogen content in the 0-20 cm soil layer decreased significantly by 65.7%-81.2%, while the ammonium nitrogen content increased by 48.7%-54.8%; the content of alkali-hydrolyzed nitrogen decreased, and the content of total nitrogen increased, but the change range was small. When the water treatment was removed(7-14 d after waterlogging), the nitrate nitrogen content increased sharply, and even recovered to the same level as CK, and the ammonium nitrogen content gradually decreased, which was opposite to the change trend of CK; the changes of total nitrogen and alkalihydrolyzed nitrogen content were consistent with the trend of CK. Then to the maturity stage of wheat, the nitrogen contents in the CK and WL treatments decreased gradually on the whole. Waterlogging at anthesis stage significantly reduced the post-anthesis nitrogen accumulation of Xiangmai 55 and Zhengmai 9023(P<0.05, the same below), and resulted in a significant decrease of nitrogen accumulation in vegetative organs and grains at maturity. The reduction of nitrogen accumulation after anthesis in Xiangmai 55 was significantly smaller than that in Zhengmai 9023. Inaddition, WL treatment significantly decreased the 1000-grain weight and grain yield of Xiangmai 55 and Zhengmai 9023, compared with CK, the yield of Xiangmai 55 and Zhengmai 9023 decreased by 25.24% and 34.81% respectively. Through the redundancy analysis of soil nitrogen content and yield and nitrogen accumulation of mature plants under waterlogging conditions, it could be seen that on the 7th day of waterlogging(the day of waterlogging termination), soil nitrate nitrogen content was positively correlated with wheat yield and nitrogen accumulation in mature plants, ammonium nitrogen and total nitrogen contents were negatively correlated with wheat grain yield and nitrogen accumulation in mature plants and less correlated with soil depth. However, there were differences between soil layers in the relationship between alkaline hydrolyzed nitrogen content and wheat grain yield, nitrogen accumulation in mature plants.【Conclusion】Waterlogging at anthesis stage significantly reduce wheat yield and nitrogen accumulation after anthesis, and the effects on various forms of soil nitrogen are mainly in the 0-20 cm soil layer. Among them, nitrate nitrogen content was positively correlated with nitrogen accumulation and grain yield of plants at maturity, while ammonium nitrogen nitrate nitrogen content was negatively correlated with nitrogen accumulation and grain yield of plants at maturity.