| Transparent plastic-film mulch combined with ridge-furrow can significantly improve crop yield.For decreasing cost of plastic-film and increasing yield benefit,we studied the crop yield and response of three soil parameters by retaining the plastic-film for three years（P3）,compared to removing old plastic-film and covering new plastic-film before planting every year（P1）.We conducted this field research on maize and board bean in the Semi-Arid Ecosystem Research Station of Lanzhou University in lanzhou,Gansu province.Maize was planted in 2017 by Transparent plastic-film mulch combined with ridge-furrow in the trial site,and the old plastic-film was retained until to 2018.We set up four treatments before planting in2018:1)retaining old plastic-mulch until harvest in 2019,maize（P3-M）;2)retaining old plastic-mulch until harvest in 2019,board bean（P3-B）;3)change to new plastic-film every year,maize（P1-M）;4)change to new plastic-film every year,bean（P1-B）.We measured the soil water content in 0-2m and crop yield in 2018 and 2019.After harvest in 2019,we measured the organic carbon content of soil and its light/heavy fraction,aggregate structure and soil enzyme activities in different aggregate sizes.Three methods were used to separate the aggregate:dry sieving,“optimal moisture”sieving and wet sieving,and soils separated by dry sieving and“optimal moisture”sieving were used to test soil enzyme activities.the main results as follows:1)P3 decreased the soil surface temperature.The average temperature in P1-B、P1-M、P3-B、P3-M during May to October in 2018 and 2019 were 18.3℃、17.3℃、16.7℃、16.0℃.2)The differences of soil water content between P1 and P3 was mainly happened in 0-60 cm.There were no significant difference on the soil water storage in0-60 cm between（P1-M and P3-M）or（P1-B and P3-B）.Compared to P1-B,P3-B decreased soil water storage in 0-2 m between growing seasons in 2018 and 2019（p=0.025）,but it turned to no significance at harvest in 2019.No significance was found between P1 and P3 in soil water storage in 0-2 m during 2018-2019 or at harvest in 2019.3)Compared to P1-M,the biomass yield and biomass water use efficiency（WUE）were decreased by 46.9%and 49%in 2018,and 41.3%and 39%in 2019.No significant difference was found between P1-B and P3-B on grain yield and grain WUE.4)Compared to P1,P3 decreased the cost of plastic-film and machine by 3210yuan·ha-1·year-1,P3 decreased the economic benefit of maize by 9360 yuan/ha,and increased the economic benefit of board bean by 8339 yuan/ha.5)P3-M significantly decreased the organic carbon content of soil and its light and heavy fraction by 25%、78.9%and 7.7%compared to P1-M.But only heavy fraction organic carbon marginally decreased in P3-B compared to P1-B,not significant（p=0.086）.6)The sensitivities between three different aggregates were different,dry sieving method was most sensitive.In wet sieving method,there was no difference between P1 and P3 in aggregates distribution or mean weight diameter（MWD）.In“optimal moisture”sieving method,P3 significantly decreased proportion of microaggregate（0-0.25 mm）by 66.2%,but had no effect on MWD.In dry sieving method,P-NT increased proportion of large macroaggregate（LM,>2 mm）and decreased proportion of microaggregate（0-0.25 mm）,and increased MWD significant-ly by 16.4%.7)The results of the distribution of soil enzyme activities in two methods of aggregate sieving were different.There was a significant difference between crop types.In dry sieving method,there was a significant difference between aggregate sizes and no difference between tillages,and soil enzyme activities was lower in bigger aggregate sizes.However,there was a significant difference between tillages and no difference between aggregate sizes in“optimal moisture”sieving.8)Using“optimal moisture”sieving,we found that P3 significantly decrease the soil enzyme activities ofβ-1,4-glucosidase（βG）in small macroaggregates（SM,0.25-1mm）and microaggregates（MIC,0-0.25 mm）,the percentage of decrease are22.2%and 27.1%.P3 significantly decreased the enzyme activities of phosphatase（P）in large macroaggregates（LM,>2 mm）and medium macroaggregare（MM,1-2 mm）,the percentage of decrease are 21.8%and 15.4%（Compared to P1）.In summary,Compared to P1,the crop yield will be decreased if planting maize in the later two years,but little effect on planting board bean.Maybe due to low soil temperature.P3 decreased the economic benefit of maize due to low yield and increased the economic benefit of board bean.P3 was a helpful tillage style to form macroaggregates,but it decreased the soil organic carbon and soil enzyme activities in part of aggregate sizes.Therefore,we do not suggest to plant maize continuously in P3 style,but board bean was acceptable in the later two years in P3 style with no soil organic carbon deficit. |
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