| Soil tillage has a direct impact on crop growth and is an effective way to improve soil quality and increase maize yield.In order to screen out the suitable tillage methods for the rain-fed area in Northeast China,a two-year field experiment was conducted with a density-tolerant maize variety（Liangyu 99）as the test material in 2020 and 2021.Four tillage methods（plow tillage（PT）,no-tillage（NT）,rotary tillage（RT）and subsoiling tillage（ST））were set up to analyze the effects of different tillage methods on soil bulk,soil porosity,maize leaf area index,maize dry matter accumulation,maize root growth and yield.The effects of different tilliage methods on maize yield increase were evaluated comprehensively.And on the basis of field experiments,HYDRUS-2D software was used to establish a soil water movement model under different tillage methods and simulate the changes of soil water under different tillage methods.The main conclusions are as follows:（1）The ST treatment was effective in improving the soil structure,reducing soil bulk and increasing soil porosity better than the PT,RT and NT treatments.The leaf area index of maize under different tillage methods showed a trend of increasing first and then decreasing,and the leaf area index of ST treatment was significantly higher than other treatments in the whole growth period of maize.The aboveground dry matter accumulation tended to increase gradually with the growth of maize,and reached the maximum value at the maturity stage.The root dry matter accumulation,root surface area,root length,root volume and root thickness of the maize showed a tendency to increase and then decrease,reached a maximum at the tassel filling stage of maize.Throughout the whole growth period of maize,the trends in dry matter accumulation and root system indexes for both years were:ST>PT>RT>NT.（2）The ST treatment increased maize yield and water use efficiency compared to other treatments.The yield of ST treatment was 666 kg·hm-2,1322 kg·hm-2 and 1752 kg·hm-2 higher than that of PT,RT and NT treatments in 2020,and 701 kg·hm-2,1144 kg·hm-2 and 1574 kg·hm-2 higher than that of PT,RT and NT treatments,in 2021,respectively.The water use efficiency of the ST treatment was 3.68%-11.88%and 2.87%-9.11%higher than the other treatments in2020 and 2021,respectively.（3）Based on the output of the HYDRUS-2D model,it can be seen that the soil profile water content fluctuated up and down with the infiltration of rainfall and evaporation of soil water,and the magnitude of fluctuation decreased with the deepening of the soil layer.The soil water content under different treatments showed that ST>RT>NT.The evapotranspiration law were the same among different treatments,with interplant evaporation showing a gradual decrease and plant transpiration showing an increasing trend followed by a decreasing trend.The transpiration and evaporation rates of the ST treatment were greater than those of RT and NT treatments.（4）The ST treatment promoted rainfall infiltration more than the RT and NT treatments,and the amount of water recharged to the soil by rainfall infiltration gradually decreased with the increase of the soil layer.The deep seepage and groundwater recharge of the ST treatment were greater than those of the RT and NT treatments.The amount of deep seepage in the field gradually increased with the increase of rainfall in the field,and the amount of groundwater recharge gradually decreased with the increase of rainfall in the field.In conclusion,subsoiling tillage can improve soil quality,reduce soil capacity,increase soil porosity,and promote rainfall infiltration.Subsoiling tillage allows maize root system to develop more into a deeper layer of soil,which promotes maize root development,and thus can absorb more nutrients and water from the soil.And subsoiling tillage increases aboveground and roots dry matter accumulation in maize,thus increasing maize yield.Therefore,subsoiling tillage is the most suitable tillage method for the study area. |
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