Effects Of Post-Anthesis Waterlogging Stress Under Different Fertilizer Levels On Yield Formation

Oilseed rape(Brassica napus L.)is the most important source of edible oil in China and play an important role in the production、circulation and trade of oil crops.The Yangtze River Basin is the main growth region of rapeseed in China.However,with the rich water resources,moist and rainy weather in the region,coupled with irrational irrigation,waterlogging stress has become one of the major adversities in rapeseed production.Flowering stage is the key stage in determining the final yield and is most sensitive to waterlogging stress.If encountering waterlogging during the flowering period,it may lead to severe yield loss of rape.Two-year experiments were conducted during 2014-2016 with different waterlogging durations and Nitrogen levels during flowering stage.The treatments were waterlogging of 0,3,6,and 9 days in pot and 0,3,and 6 days in pool with and without fertilization at flowering.Through the measurement of leaf SPAD,leaf area index,organ dry matter,yield component and yield,we determined the effects of waterlogging stress and fertilation at flowering stage on leaf senescence,accumulation and partitioning of assimilation,and yield formation in rapeseed.The results of the study will provide theoretical and technical support for further construction and improvement of the growth simulation model under the condition of waterlogging.It provides scientific basis for waterlogging stress assessment and forecasting and early warning in rapeseed production,which is of great significance for determining effective adaptability under rapeseed disaster.Based on pot and pool experiment,the results showed that the waterlogging stress decreased the number of green leaves,the relative content of chlorophyll(SPAD)and the dry weight of leaf green leaves,and accelerated the senescence of senescence.The leaves of the plant were larger than the upper leaves.Under 3 days of most waterlogging of the treatment of,the upper part of the organs did not significantly reduce,however,waterlogging of 6 days treatment significantly reduced the aboveground organs of the dry matter accumulation.The effect of waterlogging on roots was faster than that of aboveground parts.Under the condition of fertilization,the dry matter weight decreased significantly at 3 days,but the root damage was similar to that of aboveground biomass.Compared with different cultivation methods,the effect of waterlogging on pot was higher than that of pool.Under normal water management,the application of nitrogen fertilizer can significantly improve the biomass of most processed upper organs and the total dry matter weight in the shoots.However,with the increase of waterlogging time,the effect of nitrogen fertilizer on the accumulation of dry matter in the shoots and underground was declining.The dry matter weight,grain yield and harvest index of the upper part of rape were decreased with the increase of waterlogging duration.There was no significant difference in dry matter weight of aboveground and yield components under 3 days of waterlogging treatments,but the yield was significantly decreased.Under 6 days of waterlogging,aboveground dry weight,yield and yield componets decreased significantly.With waterlogging increasing each 1d at flowering time,harvest index decreased 0.008,the number of pods per plant decreased 14.71,grain number per pod decreased 0.29,1000-grain weight decreased 0.04 g,yield per plant to reduce the 1.52 g/plant.The interaction between waterlogging and fertilization could significantly increase the yield by 3.17 g/plant,and significantly increase the number of pods per plant 39.16,which could alleviate the yield loss.When the waterlogging was 6 days,the interaction between waterlogging and fertilization could reduce the yield of 2.29 g/plant,but it did not reach the significant level and had no significant effect on the yield componets.When the waterlogging 9 days,the interaction between waterlogging and fertilization can significantly reduce the yield of 4.78 g/plant,increase the yield loss.Under the condition of waterlogging,the correlation coefficient between grain yield and harvest index and 1000-grain weight was increased,and the correlation coefficient between harvest index and 1000-grain weight,aboveground dry weight and pod number was significantly improved.