| Dryland farming plays an indispensable role in ensuring global food security.However,the scarcity of precipitation and large spatial and temporal variability seriously threaten the sustainability of agricultural production in the dryland farming.Farmland mulching technology,especially plastic film mulching practice,has been widely used in dryland crop production.However,the key production resources?solar radiation,thermal and precipitation?vary greatly in different dryland areas,and the yield increase effect of farmland mulching technology will also be affected by regional climatic factors.Therefore,appropriate farmland mulching patterns according to the regional characteristics can improve the utilization rate of resources and farmland productivity,and promote the sustainable development of agriculture in dryland regions.Therefore,in this study,different mulching treatments have been set up for several years in the semi-arid?Pengyang,Ningxia Province?and semi-humid?Yangling,Shaanxi Province?areas of the Loess Plateau in China:1)ridge-furrow planting pattern?R?,2)flat planting pattern with full plastic-film mulch?P?,3)flat planting pattern with full biodegradable film mulch?B?,4)flat planting pattern with full straw mulch?S?and 5)traditional flat planting?CK?,the effects of different farmland cover measures on soil moisture?SM?,soil temperature?ST?,soil carbon and nitrogen nutrients,soil microbial community structure,and crop productivity were studied.The main results obtained are as follows:?1?Effect of different farmland mulching patterns on soil moisture and soil temperatureDifferent mulching patterns significantly affected soil temperature,and the differences between treatments gradually decreased with the development of the growth process.In the semi-arid area,the three mulching treatments all showed obvious warming effect,which was shown as P>B>R.In the semi-humid area,the average soil temperature of 0-25 cm during the whole growth period of P and R treatment increased 3.1?C and 0.6?C compared with CK.The S treatment in the two experimental areas had obvious cooling effect throughout the growing period,and the cooling effect on the soil was more obvious in the semi-arid area.Different farmland mulching patterns all had a certain moisture conservation effect in the fallow period,but it affected by different experimental regions and the precipitation patterns,the P treatment had the best water storage effect during the fallow period in the two experimental areas.In addition,the mulching treatments of the two experimental areas can effectively improve the soil water content in the early growth stage,with the development of growth period,due to the increase of biomass and plant transpiration,the mulching treatments promoted the utilization of deep soil moisture by crops in the middle stage of growth,while the surface soil water content has risen again in the late growth stage.The farmland water consumption?ET?during period of the mulching treatment showed a pattern of“low before-high middle-low after”.S treatment maintained higher soil water content than CK throughout the growth period at the two experimental areas.In addition,the ET of P treatment was the highest in the semi-arid area,and its average ET was 44.5 mm,44.1 mm,65.5 mm and 59.9 mm higher than R,B,S and CK,respectively.The ET order of each treatment was P>S>R>CK in the semi-humid area.?2?Effect of continuous mulching on soil carbon and nitrogen nutrientsContinuous mulching has different effects on soil total nitrogen?TN?and soil organic carbon?SOC?content under different mulching patterns.The TN content of the surface soil?0-20 cm?showed a gradually decreasing trend in the two experimental areas,and the plastic film?R and P?and biodegradable?B?treatments had the largest decreasing rate,followed by S and CK treatment.However,the SOC content of the surface soil under P,B and S mulching in the semi-arid area site increased slightly,while that in R and CK decreased by 0.03 and0.04 g kg-1 respectively,but they were not significantly different from that before the field trial.In the semi-humid area,except for S treatment,the SOC content of the other treatments all decreased in other two soil layers?0-20 cm and 20-40 cm?.The contents of soil dissolved organic carbon and nitrogen?DOC and DON?were the highest in the surface soil?0-20 cm?,and gradually decreased with the deepening of soil layer.The DOC content of the surface soil was the highest in S treatment,while the surface soil DOC and DON content decreased under the film mulching treatments compared with CK in the two experimental areas.There was no significant difference in DOC and DON content between the treatments in 20-40 cm and 40-60 cm soil layers.The vertical distribution of nitrate nitrogen in 0-100 cm soil profile was affected by different rainfall years.The peak value and difference of nitrate nitrogen profile of each treatment were concentrated in the upper soil?0-40 cm?when there was less rainfall in the later stage of maize growth,and more rainfall in the later growth stage would lead to the leaching of nitrate nitrogen in the harvest period,which will cause higher levels of nitrate nitrogen content in deep soil?60-100 cm?.Film mulching?R,P and B?treatments promoted the absorption of nitrogen and reduced the accumulation of nitrate nitrogen in deep soil in the two experimental areas.There was no significant difference between the distribution of nitrate nitrogen of S and CK treatment.The ammonium nitrogen content of each treatment was lower than that of nitrate nitrogen,and its distribution was similar to that of nitrate nitrogen.?3?Impact of continuous mulching on soil microbial community structureContinuous mulching resulted in changes in soil physical and chemical properties in the two experimental areas,and further led to changes in soil microbial community structure.Compared with other mulching treatments,the P treatment in the semi-arid area and the R treatment in the semi-humid area both improved the diversity and richness of soil fungi and bacteria at the same time.The change of soil physical and chemical properties was closely related to the change of soil microbial community,which can explain the change of the soil microbial community structure in more than 80%of the semi-arid area?Pengyang?and the variation of soil microbial community of more than 90%in the semi-humid area?Yangling?.The change of bacterial community was mainly affected by SM,and the change of fungal community mainly depended on soil nutrients?NO3-N,TN?and ST in the semi-arid area.However,SM and ST were the most important factors affecting the change of soil microbial community structure under different mulching measures in the semi-humid area.?4?Effect of different farmland mulching patterns on the maize growthFilm mulching?R,P and B?treatments obviously shortened the growth period of spring maize,and the plant height,stem diameter and leaf area index of maize of them were also significantly increased,and they significantly increased the biomass and proportion of dry ear weight in the total dry matter mass,which was shown as P>R>B in the semi-arid area,while the biomass of R and P treatment increased by 19.2%and 20.7%compared with CK in the semi-humid area.The S treatment delayed the growth process of spring maize in the two experimental areas,but its influence on the maize growth and development was different in normal and poor rainfall year.In the normal rainfall year,the plant height,stem diameter,leaf area index and dry matter accumulation of S treatment were lower than CK,but they were increased to different degrees in the dry year.The effect of farmland mulching patterns on dry matter transport and distribution was different in the two experiment areas.In the semi-arid area,compared with the control,the contribution rate of dry matter accumulation to grain after silking was significantly increased in each film mulching treatment?except in 2017?,and the change of dry matter transport and distribution under S treatment was affected by the rainfall year.In the semi-humid area,R and P treatments increased the amount of assimilation accumulation to grain after silking by an average of 20.9%and 21.1%compared to CK during the experimental period,the S treatment only significantly increased the amount of assimilation accumulation to grain after silking in2016,but the mulching patterns had no significant effect on the contribution rate of assimilation accumulation to grain.?5?Impact of different farmland mulching patterns on maize yield,water use efficiency?WUE?and economic benefitsThe three film mulching treatments significantly increased the maize grain yield by increasing the number of ears and 100-grain weight.In the semi-arid area,the average yield of R,P and B treatments increased by 2971,6831,and 1600 kg ha-1 over CK,in which the net income of R and P treatments has also been improved to varying degrees,and the net income of B treatment has been reduced due to the high cost of mulching materials;in addition,WUE has the highest under P treatment,followed by R,B,S and CK.In the semi-humid area,the yield increases of R and P treatments were 5.7%to 24.8%and 8.5%to 20.4%,and the economic benefits increased by an average of 1156 yuan ha-1 and 857 yuan ha-1 compared with CK,while WUE of R treatment increased by 7.4%,18.0%and 15.2%on average respectively compared with P,S and CK treatment.The yield and WUE of S treatment were significantly affected by the rainfall year types.In the normal year,the maize grain year yield decreased due to the decrease in 100-grain weight and the WUE was also reduced.In the dry year,the yield and WUE increased to varying degrees,while the economic benefits of Pengyang and Yangling were 524 yuan ha-1 and 977 yuan ha-1 lower than CK.Overall,the performance of maize grain yield and economic benefits under P treatment in the semi-arid area was obviously better than that in the semi-humid area,while the WUE and economic benefits of R treatment were the largest in the semi-humid area,and the S treatment had a greater impact on the corn yield and WUE in the semi-arid area.The changes of maize productivity under different farmland mulching patterns were closely related to changes in soil physical and chemical properties and soil microorganisms.In the semi-arid area,soil water storage before sowing?SWSS?,ST,ET,TN,and SOC were significantly correlated with grain yield,WUE,and economic benefits;while the yield,WUE,and economic benefits were mainly affected by ET and TN in the semi-humid area,which indicated that coordinating SM,ST and soil nutrients could improve crop yield in semi-arid area,but SWSS and ST were not the main factors limiting crop yield improvement in semi-humid area.In addition,soil bacterial diversity was significantly positively correlated with crop grain yield in the two experimental areas,while the fungal community mainly affected WUE.In summary,the impact of farmland mulching patterns on soil main properties and maize productivity was significantly affected by climatic conditions in different dryland areas,screening appropriate farmland mulching patterns based on the major limiting factors in different regions is effective for maintaining dryland farmland productivity.Flat planting pattern with full plastic-film mulch?P?consistently increased maize grain yield in the semi-arid area and increased the grain yield to a smaller degree in the semi-humid area,so it is more suitable for cold semi-arid areas.In the semi-arid area,the yield increasing effect of flat planting pattern with full biodegradable film mulch?B?was not sustainable,and it is weaker than that of full plastic film mulching.Ridge-furrow planting pattern?R?continuously improved maize productivity and economic benefits in the semi-humid area,while it increased interannual variation of maize yield in the semi-arid area.Although the yield increasing effect of flat planting pattern with full straw mulch?S?was not as good as that of plastic film mulching,its performance was better than that of no mulching in the dry years.Considering the effect of straw on soil fertility and the consumption of soil nutrients by plastic film mulching,the combination of film mulching and straw can improve the productivity of crops and balance the soil fertility.Considering the effect of straw on soil fertility and the consumption of soil nutrients by plastic film mulching,the combination of film mulching and straw can improve crop productivity and balance soil fertility. |
PDF Full Text Request