Change characteristics of soil oxygen content of waterlogged wheat and waterlog damage index determination

【Objective】To analyze the change characteristics of soil oxygen content in different waterlog periods of wheat,and set waterlog damage index wheat based on soil oxygen content,so as to provide a theoretical basis for accurate and timely determining waterlog degree of wheat.【Method】A waterlog experiment was carried out in 2 stages,jointing-flowering period and flowering-maturity period respectively with waterlog-resistant cultivar Yangmai 11 and the waterlog-unresistant cultivar Zhengmai 7698. Four treatments of continuous waterlog for 0(CK),5,12 and 20 d were set to determine soil oxygen content and wheat yield and to analyze the relationship between waterlog duration and yield of different winter wheat varieties under hypoxia stress and different treatments,in order to select waterlogged wheat indexes with soil oxygen content as eigenvalue.【Result】Soil oxygen content gradually decreased as time and growth period went on,and its fluctuation was closely related to natural rainfall;the decrease of oxygen content in waterlogged soil during jointing-flowering period was greater than that during flowering-maturity period;soil oxygen content in CK changed as growth period went on,which was above 20 mg/L before sowing to jointing period,decreased to around 10 mg/L from jointing period to grain filling period,and below 10 mg/L after grain filling period;in waterlog treatments,the soil oxygen content of wheat was lower than 5 mg/L in 2 growth periods,leading to a conclusion that before the end of April,soil oxygen content could be used as waterlog damage index of wheat,and the waterlogging threshold of soil oxygen content was 5 mg/L. The yield of Yangmai 11 and Zhengmai 7698 were extremely significantly negatively correlated with the days of waterlog treatment(P<0.01) and the longer the waterlogging treatment lasted,the greater the impact on the yield of wheat,regardless of whether the variety was waterlog-resistant or not. The soil relative water content greatly influenced oxygen in early growth period,and relative water content in waterlogged soil kept the soil oxygen content below 5 mg/L,yet in the late growth period,effects of relative water content on oxygen was not obvious. The relationship between wheat yield and the duration when soil oxygen was lower than 5 mg/L was analyzed,and the waterlog damage index standard of wheat based on soil oxygen content was set:during the jointing-flowering period,mild,moderate,and severe waterlog damage was determined when soil oxygen content in Yangmai 11 was lower than 5 mg/L for more than 7,17,and 25 d,Zhengmai 7698 for more than 8,18,and 24 d;mild,moderate and severe waterlog damage was determined when lowering-maturity period of Yangmai 11 and Zhengmai 7698 lasted for more than 11,18 and 27 d.【Conclusion】Taking the change characteristics of soil oxygen content when wheat is waterlogged as the waterlog damage identification standard is appropriate in wheat-planting Jianghan Plain. Before the end of April,soil oxygen content can be used as the waterlog damage index of wheat,and the threshold of the oxygen content in waterlogged soil is 5 mg/L.