【摘要】 在年降水量 4 15 mm的黄土高原中部黄绵土和年降水量 6 32 mm的黄土高原南部红油土上 ,分别以春小麦和冬小麦为供试作物进行大田试验 ,研究了地膜覆盖 (春小麦设不覆膜、播后覆膜 30 d、覆膜 6 0 d和全程覆膜 ;冬小麦设不覆膜、播后覆膜 75 d、覆膜 15 0 d和全程覆膜等 4个水平 )和施氮 (春小麦设不施氮和每公顷施氮75 kg,冬小麦设不施氮和每公顷施氮 2 2 5 kg2个水平 )对小麦产量和氮效率的影响。试验结果表明 ,覆膜对春小麦产量和吸氮量的效应因底墒、施氮、覆膜进程和生育期降雨量而异。在湿润年份 (1999年 ) ,无论施氮与否 ,在低底墒时 ,各种覆膜处理的籽粒、茎叶和干物质产量较不覆膜处理虽有增加 ,但二者之间的差异并不显著 ;在高底墒时 ,不管是籽粒 ,还是干物质 ,以覆膜 6 0 d最大 ,以不覆膜最低 ,但不覆膜与覆膜 30 d、覆膜 6 0 d和全程覆膜间差异并不显著。氮肥肥效也因底墒和覆膜进程而异 :低底墒不覆膜和覆膜 30 d的氮肥增产效果最显著 ,但随着覆膜进程的进一步延长 ,氮肥效果下降 ;高底墒时以覆膜 30 d氮肥增产效果最高 ,不覆膜最低。在极端干旱年份 (2 0 0 0年 ) ,地膜覆盖显著影响地上部分生物量 :在低底墒不施氮条件下 ,以覆膜 30 d效果最明显 ,覆膜 6 0 d和全程覆膜效果依次递减 ,不覆?更多还原

【Abstract】 Field experiments have been carried out on loess plateau in middle part with 415 mm average precipitation and in south part with 632 mm precipitation per year.In these experiments,spring wheat ( Triticum aestivum ) and winter wheat ( Triticum aestivum ) have been used as indicating crops to study the effects of plastic film mulching (for spring wheat,including non mulching,mulching for 30 days and 60 days after sowing,and mulching for the whole growing period;and for winter wheat,including non mulching,mulching for 75 days and for 150 days after sowing,and mulching for the whole growth period) and nitrogen fertilizer application (for spring wheat,including no nitrogen application and nitrogen application 75 kg N/hm 2,and for winter wheat,including no nitrogen application and nitrogen application 225 kg/hm 2 ) on wheat yield and N efficiency.The results showed that the effects of plastic film mulching on the yield and N efficiency differed according to the soil water storage amount before sowing,the application of N fertilizer,the course of plastic film mulching and rainfall in the growth periods.In 1999 with rich rainfall,no matter whether nitrogen fertilizer was applied or not,under the condition of low soil water storage before sowing,although the grain,straw and biomass yield under all the film mulching treatments increased,there was no significant difference compared with non mulching treatment (control);under the condition of high soil water storage before sowing,both grain and dry matter had the highest yield after film mulching for 60 days,and non film mulching had the lowest one.But,there was no significant difference between the non mulching treatment and film mulching for 30 days,and between film mulching for 60 days and film mulching for the whole growth period.In 2000 with the extreme drought,film mulching affected significantly the biomass yield.Under the conditions of low soil water storage before sowing and no application of nitrogen fertilizer,biomass yield increased markedly in the treatment of film mulching for 30 days,then was the treatment of film mulching for 60 days,and the last was the treatment of film mulching for the whole growth period.After applying nitrogen fertilize,the biomass yields difference between the non film mulching and the film mulching for 30 days,and between film mulching for 60 days and film mulching for the whole growth period did not reach significant level.In dealing with the plot of high soil water storage before sowing,if nitrogen fertilizer was not applied,there was not any difference,no matter how plastic film was mulched.The grain yield ranged from 1 430 kg/hm 2 to 1 482 kg/hm 2.When nitrogen fertilizer applied,the grain yield in the treatment of film mulching for the whole growth period was the highest,and there was no significant difference between the film mulching for 30 days and for 60 days.According to the average of two rates of nitrogen fertilizer application,there was no significant difference among various film mulching treatments.Because there werent notable difference of crop nitrogen content between different mulching treatments,the effect of film mulching treatment on crop uptake of nitrogen was the same as the effect on crop yield.But,it was obvious that film mulching during the earlier growth stage (e.g.film mulching for 30 days after sowing) could improve the nitrogen to transfer from straws to spikes (mainly in grain) in later growth stage.According to the analysis of the factors affecting the yield in two years experiments,the effects of film mulching on the number of spiklet and the valid number of spiklet were mainly factors affecting the grain yield.At the same time,the effects of film mulching course on the nitrogen fertilizer efficiency were related to precipitation in crop growth stage.In the year with rich rainfall,under low soil water storage before sowing,nitrogen fertilizer efficiency was the highest in the treatments of non film mulching and film mulching for 30 days,they were 30.4% and 30.3% respectively,while nitrog更多还原