Effects of waterlogging during flowering on wheat yield and soil mineral nitrogen under different nitrogen application rates
[Objective]The effects of waterlogging during flowering on dry matter accumulation and transport,yield and soil mineral nitrogen content of wheat plants under different nitrogen application rates were discussed,in order to provide a theoretical basis for the water-resistant and high-yield cultivation of wheat in the Jianghan Plain.[Method]The wheat varieties Xiangmai 55 and Yangmai 23 suitable for planting in the middle and lower reaches of the Yangtze River were used as materials.Three nitrogen application levels including N0(no nitrogen appli-cation),N1(pure nitrogen 135 kg/hm2),N2(pure nitrogen 180 kg/hm2)were set and watered for 7 days at the flowering stage by potting method.The changes of SPAD value in flag leaves,dry matter accumulation and transport in the ground,grain yield and soil mineral nitro-gen content of wheat were analyzed.[Result]Waterlogging during flowering period significantly decreased SPAD value in flag leaves and dry matter accumulation in aboveground parts of wheat.SPAD value in flag leaves and dry matter accumulation in aboveground parts decreased by 8.61％to 39.78％,and dry matter accumulation in aboveground parts decreased by 4.49％-12.24％,and the decreasing range de-creased with the increase of nitrogen application rate.Under waterlogging,with the increase of nitrogen application rate,pre-flowering dry matter transfer and contribution rate of wheat,post-flowering dry matter accumulation increased by 35.39％-58.37％,6.04％-21.88％and 8.94％-29.32％,respectively.During waterlogging period(0-7 days after anthesis),soil nitrate nitrogen content decreased signifi-cantly by 41.81％-63.50％;The content of ammonium nitrogen increased significantly by 21.89％-62.15％.After removing water,the nitrate nitrogen content increased and the ammonium nitrogen content decreased from 7 to 21 days.From 21 to 28 days,nitrate nitrogen con-tent decreased and ammonium nitrogen content increased.Under waterlogging treatment,when increasing nitrogen application,nitrate nitro-gen and ammonium nitrogen content increased.Waterlogging in flowering period led to wheat yield reduction,and the 1000-grain weight re-duction was the main factor.The wheat yield of N1 and N2 was increased by 229.75％-235.32％and 290.28％-358.12％respectively under waterlogging conditions compared with no N application.[Conclusion]Waterlogging significantly decreased SPAD value,dry matter ac-cumulation,yield and nitrate nitrogen content of wheat flag leaves,but increased ammonium nitrogen content of soil.Under the condition of 0-180 kg/hm2,increasing nitrogen application could alleviate the damage of waterlogging and reduce the decrease of wheat yield.
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