Effects Of Seeding Rate On Yield And Water Use Efficiency Of Film Mulched Wheat Under Different Pre-sowing Soil Moisture

The objective of this study was to investigate the effects of pre-sowing soil moisture and seeding rate on yield and water use efficiency of film mulched wheat by means of a field experiment.The experiment involved four treatments as high pre-sowing soil moisture,low pre-sowing soil moisture,high seeding rate,low seeding rate.The main results and conclusions obtained were as follows:1)The trends of population dynamics and biomass dynamics of winter wheat covered with plastic film under high and low seeding rate treatments were consistent under both high and low pre-sowing soil moisture levels.The population number and biomass were higher at high seeding rate than those at low seeding rate,but there was no significant difference between two seeding rates.At harvest,seeding rate had insignificant effect on winter wheat biomass,but the interaction between seeding rate and pre-sowing soil moisture had significant effect on winter wheat biomass.2)The grain yield between high and low pre-sowing soil moisture was significant.Compared with low seeding rate,high seeding rate increased the number of spikes and 10³kernels weight of winter wheat,but decreased the number of grains per spike,but difference was not significant.Under low pre-sowing soil moisture,at low seeding rate average grain yield was 4284 kg ha^-1,at high seeding rate average grain yield was 3743 kg ha^-1,the yield of low seeding rate was higher than that of high seeding rate.But there was also insignificant between them.Under high pre-sowing soil moisture,at low seeding rate average grain yield was 4272 kg ha^-1,at high seeding rate average grain yield was 4787 kg ha^-1.Compared with low seeding rate,high seeding rate significantly increased winter wheat yield by 12%.Therefore,the interaction between pre-sowing soil moisture and seeding rate has a significant impact on grain yield of winter wheat.3)Evapotranspiration at high seeding rate was higher than that at low seeding rate under pre-sowing soil moisture.The high seeding rate increased evapotranspiration by 17.4 mm,reduced water use efficiency of grain by13%,decreased water use efficiency of aboveground biomass by 4.6%,but the differences were not remarkable.Compared with low seeding rate,high seeding rate increased evapotranspiration and water use efficiency,but the difference was not significant.Low pre-sowing soil moisture significantly reduced water evapotranspiration of wheat and improved grain water use efficiency compared with high pre-sowing soil moisture.There was no significant interaction between pre-sowing soil moisture and seeding rate on evapotranspiration and water use efficiency.4)Under low pre-sowing soil moisture high seeding rate increased the apparent translocation amount of water soluble carbohydrates by 364 kg ha^-1,but decreased the water soluble carbohydrates apparent translocation ratio by 2.7%compared with low seeding rate,the difference was not significant.Under high pre-sowing soil moisture high seeding rate increased apparent translocation amount of water soluble carbohydrates by 135.8 kg ha^-1,but decreased the water soluble carbohydrates apparent translocation ratio by 9.2%compared with low seeding rate,and the difference was not significant either.The interaction between pre-sowing soil moisture and seeding rate had no significant effect on water soluble carbohydrates accumulation,water soluble carbohydrates apparent translocation amount and water soluble carbohydrates translocation ratio.On the whole,under the conditions of experimental years on the Loess Plateau,compared with low pre-sowing soil moisture,high pre-sowing soil moisture can significantly improve winter wheat yield,increase evapotranspiration and decrease water use efficiency.Increasing seeding rate can significantly increase winter wheat yield and water use efficiency under high pre-sowing soil moisture.But under low pre-sowing soil moisture,increasing seeding rate reduces winter wheat yield and water use efficiency.Thus,seeding rate should be adjusted according to pre-sowing soil moisture.