开花期渍水对土壤不同形态氮素含量及小麦氮素积累运转和产量的影响

【目的】探讨开花期渍水对土壤不同形态氮素含量的影响及其与小麦籽粒产量、植株氮素积累量的关系，以期为江汉平原小麦抗渍栽培提供理论依据。【方法】采用大田裂区试验，以襄麦55和郑麦9023为试验材料，设不渍水（CK）和开花期连续渍水7 d（WL）处理，测定土壤不同形态氮素含量、小麦植株氮素积累量及产量和产量结构等指标，并分析土壤不同形态氮素含量变化与籽粒产量、植株氮素积累量的关系。【结果】 0~20 cm土层各形态氮素含量对渍水的反应强度较20~40 cm和40~60 cm表现更剧烈。与CK相比，WL处理下（渍水后0~7 d），0~20 cm土层硝态氮含量显著下降，下降幅度达65.7%~81.2%，铵态氮含量则上升48.7%~54.8%；碱解氮含量有所下降，总氮含量上升，但变化幅度较小。当撤去水分处理后（渍水后7~14 d），硝态氮含量急剧上升，甚至恢复至与CK相同水平，铵态氮含量逐渐下降，与CK变化趋势相反；总氮和碱解氮含量变化与CK趋势一致。随后至小麦成熟期，CK和WL处理下各氮素含量总体上均逐渐降低。开花期渍水显著降低了襄麦55和郑麦9023的花后氮素积累量（P<0.05，下同），并导致成熟期营养器官氮素积累量和籽粒氮素积累量均显著下降；襄麦55花后氮素积累量下降幅度显著小于郑麦9023。此外，WL处理显著降低了襄麦55和郑麦9023的千粒重和籽粒产量，与CK相比襄麦55和郑麦9023的产量分别降低25.24%和34.81%。通过对渍水条件下土壤各形态氮素含量与产量及成熟期植株氮素积累量的冗余分析可知，渍水第7 d （渍水终止当天）土壤硝态氮含量与小麦产量和成熟期植株氮素积累量均呈正相关，铵态氮和总氮含量与小麦籽粒产量和成熟期植株氮素积累量呈负相关，与土层深度关系较小；碱解氮含量与小麦籽粒产量和成熟期植株氮素积累量的关系存在土层间差异。【结论】开花期渍水显著降低小麦产量和花后氮素积累量，对土壤各形态氮素的影响主要在0~20 cm土层，以硝态氮和铵态氮含量变化对渍水的响应最敏感，其中硝态氮含量与成熟期植株氮素积累和籽粒产量呈正相关，而铵态氮与成熟期植株氮素积累和籽粒产量呈负相关。

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.