Effects Of Different Tillage Patterns On Soil Physical Properties And Crop Yield Under Cropping System In Dark Loessial Soil

The Weibei Highland located in the south of the Loess Plateau has scant water resource and unequal seasonal distribution of precipitation,which adversely affects the growth of winter wheat and spring maize.Dark loessial soil is the main cultivated soil in the Weibei Highland.However,soil compaction and the decreased regulation capacity of water,fertilizer,gas,and heat in dark loessial soil are becoming increasingly serious.Therefore,screening reasonable cropping systems and tillage patterns to maintain good soil structure and improve water storage for increasing crop production is receiving more and more attention.In this study,a night-year?2007-2016?fixed-site experiment in the Weibei Highland,with six tillage treatments under conditions of wheat-maize rotation and maize-maize rotation was set up.In mid-June 2016,soil samples were collected to study the effects of conventional tillage?CT/CT?,no-tillage?NT/NT?,subsoiling tillage?ST/ST?,no-tillage/subsoiling tillage?NT/ST?,conventional tillage/no-tillage?CT/NT?and conventional tillage/subsoiling tillage?CT/ST?on soil bulk density,soil moisture content and the distribution and stability of soil aggregates.The aim of this study was to screen suitable wheat cultivation and tillage patterns for dryland farming in Weibei dryland area via exploring the relationship between wheat yield,soil water use efficiency?WUE?,and soil physical properties.The experimental study results are as follows:?1?The effects of different tillage patterns on the soil bulk density and soil moisture content were different.Under the conditions of wheat-maize rotation and wheat-wheat rotation system,soil bulk density in the NT/ST and NT/NT treatments was significantly higher than that in CT/CT treatment;ST/ST significantly decreased soil bulk density of 20-35 cm soil layer by 6.7%and 7.0%relative to CT/CT.Under wheat-maize rotation system,compared to CT/CT treatment,NT/ST significantly increased soil water content in 0-50 cm soil layers,however,in the wheat-wheat rotation system,NT/ST had lower water content than CT/CT treatment in 10-50 cm soil layer.Under the wheat-maize rotation system and wheat-wheat rotation system,soil water content in the NT/NT treatment was significantly higher in the surface soil than other treatments,compared with CT/CT treatment.Soil water content of the ST/ST treatment in the 10-35 cm soil layerwas significantly higher than that in CT/CT treatment.In view of different cropping systems,the average bulk density and soil water content in the 0-50 cm soil layer under wheat-maize rotation system were higher than that under wheat-wheat rotation system,in which the difference in soil water storage was no significant.The soil water storages in the NT/ST,ST/CT,CT/NT,and NT/NT treatments under wheat-maize rotation system were significantly higher than that under wheat-wheat rotation system,but ST/ST and CT/CT treatments show opposite results.?2?The effects of different tillage patterns on the distribution and size of soil aggregates were different.Under wheat-maize rotation system,the WR_0.25.25 content of the NT/NT and NT/ST treatment was higher than CT/CT;in 35-50 cm soil layer,the MWD values of NT/NT and ST/ST treatments were significant 26.5%and 32.4%higher than CT/CT treatment.Under wheat-wheat rotation system,NT/NT,ST/ST and NT/ST treatments all increased soil WR_0.25content and MWD value,but reduced the proportion of aggregate destruction?PAD?,except for20-35 cm soil layer.Overall,the content of soil water-stable aggregate with the particle size>0.25 mm(WR_0.25)in the wheat-wheat rotation system was lower than that in the wheat-maize rotation system,and the content of mechanical stable aggregate with the particle size>0.25 mm was higher than that of the wheat-maize rotation system.The MWD values of the water-stable aggregate in the wheat-maize rotation system were higher than those in the wheat-wheat rotation system.?3?The effects of different tillage patterns on wheat yield and WUE.The yield and soil WUE of NT/ST treatment were higher than other treatments.Compared with CT/CT treatment,crop yield and soil WUE of NT/ST treatment were increased by 19.3%and 7.1%,respectively,in the wheat-maize rotation system.Under wheat-wheat rotation system,crop yield and soil WUE of NT/ST treatment were increased by 14.3%and 29.4%,respectively.Under the two cropping systems,soil WUE of the wheat-maize rotation system was higher than that of wheat-wheat rotation system.?4?Relationship between soil physical properties,yield and WUE under different tillage patterns.Under wheat-maize rotation system,crop yield was positively correlated with WR_0.25in 20-35 cm soil layer and soil water content in 10-20 cm,20-35 cm and 35-50 cm soil layer,but was negatively correlated with PAD in 20-35 cm soil layer.Additionally,soil WUE was positively correlated with the soil water content in 10-20 cm,20-35 cm and 35-50 cm soil layer.However,under wheat-wheat rotation system,crop yield was positively correlated with WR_0.25in 35-50 cm soil layer,but was negatively correlated with PAD in 35-50 cm soil layer and soil water content in 20-35 cm soil layer.Additionally,in 10-20 cm soil layer,soil WUE was positively correlated with soil bulk density,soil water content,WR_0.25 and MWD,but was negatively correlated with PAD.Comprehensively,NT/ST,NT/NT treatment increased soil aggregate content and stability,improved soil structure,and improved crop yield and soil WUE under different tillage patterns,in which NT/ST treatment had the best effect.Moreover,compared with wheat-wheat rotation system,the wheat-maize rotation system improved soil water content,water-stable aggregate,crop yield and soil WUE.