Effects Of Integrated Plastic Mulch Rice Management On Yield,Soil Temperature And Water Content,and Crop Nitrogen Use In The Hilly Area Of Southwest China

The rice grain yield in the hilly area of Southwest China,is highly limited by seasonal drought and low temperature in the early rice growth period.An integrated plastic mulch rice management(IPMRM)was developed in the area,it integrates dry rice-nursery,ridge cultivation with plastic mulching,furrow irrigation and triangular transplanting.It has potential to regulate the soil water and temperature conditions during rice growth period,and to promote and stablilize rice yield.An in-situ field experiment(2011-2015)examining the effect of IPMRM on the grain yield,soil temperature and water content,and crop nitrogen use in the hilly area of southwest China.The main conclusions are as follows:Firstly,IPMRM improved rice yield and stabilized the yield whether it is drought or rainy year in southwest China.A field experiment from 2011 to 2015 was conducted on three paddy fields.The 5-year average rice yield under IPMRM was 8706 kg ha-1,in the range of 8181 to 9267 kg ha-1,the coefficient of variation was 7.6%.On the contrary,the 5-year average rice yield under traditional rice management(TRM)was 6700 kg ha-1,in the range of 4974 to 7992 kg ha-1,the coefficient of variation was 17.6%,showed highly fluctuating by rainfall and temperature.In comparison to TRM,IPMRM promoted the rice tiller development,with 7 to 13 tillers higher recorded in the maximum tillering stage per cluster,and 1-6 per cluster higher at the end of tillering stage.IPMRM significantly increased the rice aboveground biomass by 21.0%-99.2%in different growth periods and the aboveground N uptake by 27.5%-104.0%.The number of productive tillers was significantly increased by 36.5%,resulting in a 29.9%increase in grain yield.Secondly,the water retention capacity and warming effect of IPMRM were the key factors of rice yield-improving.In 2011 and 2014(drought year),soil water was the key factor in rice yield,the rice tiller under TRM was highly related to the accumulated rainfall in rice tillering stage,the tiller number under IPMRM was less affected by rainfall.The water retention capacity of IPMRM was an important factor in yield-improving.In 2014,soil water was the important factor in rice yield.The tiller number was highly related to the accumulated rainfall under IPMRM and TRM,the water retention capacity and warming effect of IPMRM increased grain yield by 27.9%.In 2015,the soil water content in the 0-20 cm depths were higher than the threshold for rice root growth(80%of saturated water content)over the rice growing season,in this situation,temperature was the important factor in rice yield,the warming effect of IPMRM,particularly in the tillering stage,stimulated early growth and stronger tillering.Compared with TRM,Tsoii of 0-20 cm depths in IPMRM was 4.67?C higher during the early tillering stage.And>10? soil effective accumulated temperature also improved,with distinct increase at the maximum tillering stage(80.5?·d).The number of productive tillers and grain yield increased by 68.8%and 49.8%compared to TRM.Thirdly,promoting the uptake and utilization of nitrogen(N)is also a key factors of rice yield-improving.An in-situ field experiment(2011-2015)examining the effect of three nitrogen levels(0,120.and 180 kg ha-1)was undertaken.To investigated rice yield,aboveground N uptake,and the soil surface N budget.Compared with TRM,IPMRM significantly improved rice grain yield(by 21%-43%),straw biomass(by 26%-43%),and aboveground N uptake.At the same N level,traditional N use efficiency(NUE),nitrogen fertilizer availability ratio(NFAR)and real nutrient use efficiency(RNUE)were increased.IPMRM significantly improved 15N recovery efficiency(by 10%percentage point)and significantly reduced potential 15N losses(by 8%-12%percentage point).Among all treatments,the 120 kg ha-1 level in the IPMRM had the highest 15N recovery efficiency(32%),15N residual efficiency(29%),and the lowest potential 15N loss(39%).IPMRM significantly increase the N uptake and utilization of rice,which was closely related with the water retention capacity and warming effect under IPMRM,thereby increasing the rice yield.After rice harvest,the replenishing effect,which was the fertilizer N supplement to the soil N consumption,was found to be deficient(-30.9?-48.6 kg ha-1)in each treatment.And the soil surface N budget of all treatments recorded a surplus(68.9-146.4 kg ha-1),the soil surface N budget of the IPMRM was lower than the TRM,as well as having a minor level of risk of N loss to the environment.The results of this study showed that IPMRM resulting in a high and stable grain yield,and the soil temperature,water content,and crop nitrogen use under IPMRM were preliminarily clarified.And provide a scientific basis for the further optimization and application potential of IPMRM,with high yield,high utilization and sustainability,in hilly rice cultivation regions with similar climatic and environmental conditions.