Study On Dynamic Of Maize(zea Mays L.)yield,soil Water And Soil Carbon Under The Dry-farming Plastic Mulching System Of Ridge And Furrow

Ridge-Furrow with full plastic film mulch system?RFM?can improve agriculture productivity in arid and semi-arid region,it has been widely promoted and applied in the past few decades.In present research,field experiment in maize?Zea mays L.?farmland in Loess Plateau was conducted to study the long-term variation of corn yield,soil water balance and soil organic carbon pool under the plastic mulching system of ridge and furrow.From 2012-2018,we conducted a field experiment at the semi-arid ecosystem research station 36.03°N,104.42°E,2318 m altitude)of Loess Plateau run by Lanzhou University.Annual precipitation is 320 mm and annual air temperature is 6.7?.Totally 6 treatments were set:?1?Bare ground without mulching;?2?Bare ground with mulching;?3?maize planting,no plastic mulch and no nitrogen fertilizer;?4?maize planting,plastic mulch but no nitrogen fertilizer;?5?maize planting,nitrogen fertilizer without plastic mulch;?6?maize planting,plastic mulch with nitrogen fertilizer.The conclusions of the study are as follows:1.Compared with treatments without mulching,plastic mulch increases maize grain yield,as well as 100-kernel weight and the total biomass,with increment of 355%,107%and 131%,respectively.The coefficient of variation?CV?and the sustainability yield index?SYI?are used to evaluate the stability and sustainability of maize grain yield.Compared with the treatments without plastic mulching and nitrogen fertilization,under cultivation with plastic mulch and nitrogen application,the coefficient of variation?CV?of maize yield is the lowest with value of0.13,and the sustainability yield index?SYI?is the highest with value of 0.74.2.RFM improves the maize water use efficiency?WUE?in growing season and precipitation storage efficiency?PSE?in non-growing season.The 7-year average WUE in treatments of no-mulch and no-nitrogen application,mulch and no-nitrogen application,no-mulch and nitrogen application,mulch and nitrogen application are 3.96 kg ha^-1 mm^-1,13.8 kg ha^-1 mm^-1,5.2 kg ha^-1mm^-1 and 18.5 kg ha^-1 mm^-1,and the average PSE are-21%,62.5%,18.2%and 77.9%,respectively.Nitrogen fertilization also increases maize water use efficiency and non-growing season precipitation storage efficiency.The WUE and PSE of treatment with N application are34.0%and 24.6%higher than that of treatment without N fertilization under film mulching.The higher PSE in non-growing season plays the key role in maintaining the soil water balance in RFM system.Plastic mulch increases the water consumption in growing season but also increases water recharge in non-growing season,which ensures the water balance in the whole year.Furthermore,plastic film mulching increases water content in 0-5 m soil profilm,indicating that film mulching doesn't cause the water shortage in deep soil profile.3.In treatments of uncultivated crops,plastic film mulching decreases the total organic carbon?SOC?and light fraction organic carbon?LFOC?content,while the heavy fraction organic carbon?HFOC?does not changed.After planting corn,plastic film mulch reduces the content of LFOC and has no effect on SOC and HFOC.However,when nitrogen fertilizer treatment is applied,plastic film mulching has no effects on all kinds of carbon,including LFOC,HFOC and SOC.From the perspective of the total organic carbon structure,in the treatments of no fertilization,plastic mulching reduced the proportion of LFOC in the total organic carbon of the soil,while increased the proportion of HFOC.After applying nitrogen fertilizer,plastic film mulch has no effect on the proportion of light and heavy components in the total organic carbon of the soil.4.Plastic film mulching,corn planting and nitrogen fertilizer application change the content of newly derived carbon in the soil light fraction organic carbon and heavy fraction organic carbon pool.The newly converted carbon is the amount of carbon renewal in the soil organic carbon pool from the beginning to the end of the experiment.Our results show that the renewal ratio of the LFOC pool is significantly higher than that of HFOC pool.At the harvest time?2018.10?,after 7years of trials,in the treatment of no crops,because there is no carbon input from crops,the proportion of new carbon in soil LFOC and HFOC pools are significantly lower than that of treatments with corn planting.After planting corn,in treatments of no-mulch and no-nitrogen application,mulch and no-nitrogen application,no-mulch and nitrogen application,mulch and nitrogen application,contents of newly derived carbon in 0-30 cm LFOC pools are 0.27 g kg^-1,0.10 g kg^-1,0.19 g kg^-1,0.13 g kg^-1,account for 40.3%,22.3%,39%,and 29.7%,respectively.And,contents of newly derived carbon in 0-30 cm HFOC pools are 0.33 g kg^-1,0.34 g kg^-1,0.45 g kg^-1,0.47 g kg^-1,which account for 6.8%,8.5%,7.6%and 9.2%.Compared with the non-mulch treatment,plastic film mulching reduces the content and proportion of new carbon in the light fraction organic carbon,indicating that the plastic film mulching increases the loss of new carbon in the LFOC.Contrary to LFOC,plastic film mulching increases the content and proportion of new carbon in the heavy fraction organic carbon,promotes the accumulation of new carbon in HFOC pool.Furthermore,under the mulched treatment,N fertilization increases the content and proportion of both LFOC and HFOC.5.Plastic film mulching and planting corn increase the temperature sensitivity of soil respiration(Q₁₀),and the application of nitrogen fertilizer has no effect on the temperature sensitivity of soil respiration.Compared with the treatment of no crops,the soil CO₂ emissions increase after planting corn.The effect of plastic film mulching on soil CO₂ emissions depends on the growth stage of corn.During the period of about 60-130 days after corn planting,film mulching increases soil CO₂ emissions,but from the perspective of the entire growing season,the effect of plastic film mulching on soil respiration is not significant.To sum up,results of 7-year experiment show that plastic film mulching with ridge and furrow is good for increasing the grain yield of dry-farming maize.At the same time,plastic film mulching with ridge and furrow system stores more water in non-growing season which guarantees the soil water balance.Furthermore,film mulching and N fertilization increase maize biomass and then increase soil carbon input,so the soil organic carbon pool maintains a balance.All above indicate that RFM system is a sustainable dry-farming planting technology to get high yield.