Effects Of Plastic Film And Straw Mulching On Soil Aggregate Carbon Distribution And Enzyme Activities Of Spring Maize In Weibei Upland

To investigate the effects of different surface mulching measures on the distribution of carbon and enzyme activity in spring maize soil aggregates,this study relied on a long-term localization experiment that began in 2012.Soil aggregates in the 0-20 cm layer under straw and plastic film mulching were the main experimental objects,with non-covered soil as the control.The distribution and stability of soil aggregates,soil functional groups,soil enzyme activity,and soil nutrients were compared and analyzed to study the effects of different mulching types on the distribution of carbon in aggregates and the physical,chemical,and biological properties of the soil.This research aims to explore the effects of cover measures on soil conservation and improvement in the Wei Weibei Dryland region,providing a theoretical basis for the sustainable development of the local ecosystem.The main conclusions of the study are as follows:1.In the aggregates,the proportion of particles with a diameter of 0.25-2 mm is consistently above 50% at all stages.The proportion of particles with a diameter of 0.25-2 mm significantly increased under straw mulching treatment in the pre-sowing period,while it increased under plastic film mulching treatment during the silk stage.At the same time,the content of particles with a diameter greater than 2mm was significantly reduced.Straw mulching had the highest increase in soil aggregate mean weight diameter(MWD),reaching up to 11.84%,while the increase in geometric mean diameter(GMD)was up to 30.00%.When describing soil stability under straw mulching,GMD is a better indicator to choose.2.Compared with the uncovered treatment,both straw and plastic film mulching significantly increased the content of physically protected carbon,chemically protected carbon,biochemically protected carbon,and physically-biochemically protected carbon in soil aggregates of spring maize in dryland.The highest increases were 31.03%,81.12%,40.44%,and 75.13%,respectively.Meanwhile,the plastic film mulching significantly reduced the content of physically-chemically protected carbon,with decreases of 5.62%,11.36%,and 5.36%during the pre-sowing period,silk stage,and harvest period,respectively.As the growth and development of spring maize progressed,the content of physically protected carbon and physically-chemically-biochemically protected carbon in aggregates first increased and then decreased,while the content of chemically protected carbon,biochemically protected carbon,and physically-chemically protected carbon gradually increased,but the differences in carbon component content over time were not significant.3.The most abundant functional group among the four major organic carbon functional groups in the reunion body is the alkoxycarbon at 45-110 ppm,with a relative content between 38.80%-59.34%;the second highest relative content is the alkyl carbon at 0-45 ppm,followed by the aromatic carbon at 110-160ppm;and the lowest content is the carboxyl carbonyl carbon at 160-220 ppm,with a relative content of only 4.03%-21.29%.The stability of organic carbon under three different cover measures is ranked as straw mulching > film mulching > no mulching.4.During the three critical stages of growth and development,compared with the no mulching treatment,straw mulching significantly increased the enzyme activities related to carbon and nitrogen cycling in soil aggregates.The enzyme activity related to carbon cycling increased up to 27.95%,while the enzyme activity related to nitrogen cycling increased up to 36.32%.Plastic film mulching significantly enhanced the extracellular enzyme activity related to phosphorus cycling,with the maximum increase ranging from 31.14% to 42.73% across the three stages.The enzyme activity related to carbon cycling decreased with a reduction in aggregate size,while the enzyme activity related to nitrogen and phosphorus cycling initially increased and then decreased,reaching the highest value in the 0.25-2 mm size range.As the planting period progressed,the enzyme activities related to carbon and nitrogen cycling decreased initially and then increased,while the AKP enzyme activity decreased.Compared with plastic film cover and no cover,straw cover significantly increased the contents of organic carbon,total nitrogen,available phosphorus,and available potassium in soil aggregates of different sizes,with significant differences(P<0.05).Among the four size groups,the enzyme activities related to carbon and nitrogen cycling were positively correlated with the contents of organic carbon,total nitrogen,and available phosphorus,while the extracellular enzyme activity related to phosphorus cycling showed a negative correlation with these factors.In summary,both mulching and straw mulching have certain effects and effects on soil quality improvement: straw mulching can be used as exogenous carbon input to soil,improve soil extracellular enzyme activity,improve soil stability,and provide a good environment for crop growth and development.Mulching can optimize soil hydrothermal conditions and meet the needs of crop growth and development.