Effects Of Tillage And Straw Returning On Soil Properties At Different Depths In Semi-arid Area Of Western Liaoning

Both the plough layer and below the plough layer are important sources of water and nutrients for crop growth,while the changes of soil properties below the plough layer are relatively less concerned.It is of great significance for the sustainable development of agriculture in the semi-arid area of western Liaoning to explore the impact of the transformation of long-term rotary tillage to other tillage methods(no tillage,subsoiling and tillage)on different levels of soil quality.Based on the long-term positioning experiment of tillage and straw returning to the field(started in 2016),in the autumn of 2020,by collecting 8treatments,namely 4 tillage methods(no tillage,rotary tillage,subsoiling and tillage)and 2returning methods(straw clearing and returning),0-5,5-10,10-20,20-30,30-40 and 40-60 cm soil samples,5 soil physical,7 chemical and 4 biological indexes were measured,To explore the effects of different tillage and straw returning methods on soil properties at different levels,the influence degree of various influencing factors on soil properties,and to evaluate the effects of different treatments on soil health at different levels.The main results are as follows:1.No tillage significantly improved the soil properties of 0-5cm and 5-10 cm in the surface layer.In terms of physical properties,compared with other tillage,no tillage increased the proportion of large aggregates(25-42%).Although the soil bulk density increased by 19-32%,the field water capacity and effective water capacity increased by 12% and 22%respectively;In terms of chemical and biological properties,no tillage increased the contents of available nitrogen,phosphorus and potassium in the surface layer.The content of organic matter increased by 30% on average,and the surface microbial biomass carbon and nitrogen increased by 150% and 80% on average,respectively.Compared with no tillage,rotary tillage and tillage,subsoiling significantly improved the soil physical properties of 20-40 cm.In 20-30 cm,the soil bulk density decreased by 10-19%,the aerated porosity increased by 17-40%,and the effective water capacity increased by 3-14%;At 40-60 cm,the overall difference of each index is not significant.2.Compared with straw stubble clearing,straw returning under different tillage methods has improved most soil properties,but the effects are different between different treatments.Compared with stubble clearing,the proportion of soil large aggregates in 0-5cm and 5-10 cm of the surface layer increased by 25% and 32% respectively,the soil water holding capacity increased by 2% and 4% respectively,the content of available nitrogen,phosphorus and potassium increased by 33-70% and 28-66% respectively,and the content of microbial biomass carbon and nitrogen increased by 45-51% and 23-40%.Under the conditions of rotary tillage,subsoiling and tillage,compared with stubble clearing,the above indexes increased by only 2-13% and 2-5%,0.2-1% and 0.5-3% in 0-5cm and 5-10 cm soil layers 17-63% and 4-41%,0.2-36% and 34-36%.In the other layers,the improvement effect of no tillage straw returning to the field compared with clearing stubble is gradually reduced compared with that under rotary tillage,subsoiling and tillage.3.The interaction between tillage methods and soil depth significantly affected(P <0.001)soil properties.The interaction between tillage methods,straw returning and soil depth had the greatest impact on physical indexes,followed by biological indexes and chemical indexes.The results of soil health evaluation showed that the health score of no tillage straw returning to the field was higher in 0-20cm;The percentage of subsoiling straw returning to the field is higher in 20-40cm;In 40-60 cm,there was no significant difference in scores between different treatments.4.No tillage and straw returning significantly improved the yield and yield stability of maize.Compared with other treatments,no tillage straw returning increased corn yield by 8-11% in wet years,4-18% in dry years,42-151% in dry years and 38-144% in stability of corn yield.The yield of no tillage straw stubble clearing treatment was similar to that of other tillage methods,and even decreased.To sum up,in the semi-arid area of western Liaoning,the short-term transformation to no tillage straw mulching mode has significantly improved the surface soil properties and corn yield and stability,while the transformation to subsoiling mode has improved some deep soil properties.Although it has increased production,the effect is limited.