| The problem of “shallow,solid,and small”in the plough layer has limited to the ability of storing and supplying fertilizer in The Lime Concretion Black Soil and the continuous increase of crop yield.In order to identify the effects of subsoiling depth on topsoil properties,crop growth,crop yield and water use efficiency and to provide insight for establishing the suitable subsoiling depth in Lime Concretion Black Soil.A long-term field experiment with four treatments of subsoiling depth of 30 cm(SS30),40 cm(SS40),50 cm(SS50)and 60 cm(SS60)and rotary tillage(RT)as a control was carried out with the field contrast design between 2014 and 2015,to study the effects of different subsoiling depth on soil property,crop growth,crop yield and water use efficiency.The results were as follows:1.Subsoiling could significantly reduce soil compaction,increase soil moisture content,increase soil porosity,make soil three-phase R value more suitable,and improve soil physical properties effectively.Among the different depths of subsoiling,SS60 was the best.Compared with RT,the average soil compaction of SS60 cm decreased by 17.9%,the the average soil moisture of SS60 increased by 14.1%..SS60 cm reduced the soil three-phase R value in the 15-60 cm soil layer by 52.6%.The soil porosity in 15-40 cm layer of SS60 increased by 135.4%.2.Subsoiling changed the distribution and content of nutrients in soil.Different depths of subsoiling had different effects on different soil layers.In winter wheat period,the nutrients in 15-60 cm layer of SS40 was the highest.The soil organic matter,total N content,available P content and available K content of SS40 was 27.3%,18.6%,54.1% and 12.8% higher than RT respectively,but there was no significant difference between SS30.In summer maize period,the soil organic matter content and total N content in 15-60 cm layer of SS50 was the highest,and it was 18.7% and 33.0% higher than RT respectively.The soil available P content and available K content in 15-60 cm layer of SS60 was the highest,and it was higher 35.8% and 11.3% than RT respectively.There was no significant difference between SS50 and SS60.3.Subsoling could significantly promote the soil respiration rate,and the impact on the summer maize was greater than the winter wheat.Subsoiling also changed soil microbial community composition.In winter wheat period and summer maize period,the average soil respiration rate of subsoiling was 24.11% and 41.3% higher than that of RT respectively.Among the different depths of subsoiling,SS60 was the highest in winter wheat period,and it was 39.7% higher than RT;SS60 was the highest in summer maize period,and it was 63.7% higher than RT.In 0-15 cm layer,the percent of Proteobacteria in subsoilng was lower than RT.Subsoiling increased the percent of Proteobacteria and Actinobacteria in 30-40 cm layer,and increased the percent of Actinobacteria in 40-50 cm layer,and increased the percent of Acidobacteria in 50-60 cm layer.4.Subsoiling could increase the crop biomass and crop nutrient accumulation.,promote root growth and increased yield.Among the different depths of subsoiling,the winter wheat biomass of SS40 was the highest,it was 29.5% higher than RT,but there was no significant difference with SS30;the summer maize biomass of SS50 was the highest,it was 13.2% higher than RT,but there was no significant difference with SS40.Root length,root volume,root surface area,and root dry weight density of SS40 was the highest in winter wheat period,but there was no significant difference between SS30 and SS40;Root length,root volume,root surface area,and root dry weight density of SS50 was the highest in summer maize period,and its difference with others were significant.The winter wheat yield of SS30 was the highest,and the summer maize yield of SS50 was the highest.The total crop yield of SS30 was the highest,it was 12.2% higher than 12.2%,but there was no significant difference in crop yield between SS30 and SS40.5.Subsoiling increased water use efficiency and economic benefits.The water use efficiency in winter wheat period,summer maize period and whole year of subsoiling was significantly higher than that of RT,Compared with RT,the water use efficiency in winter wheat period of subsoling increased by 10.8%,the water use efficiency in summer maize period of subsoling increased by 7.0%,the water use efficiency in whole year of subsoling increased by 8.7%.In winter wheat period,the water use efficiency of SS30 was the highest,it was 15.7% higher than RT,but there was no significant difference between SS30 and SS40;In summer maize period,the water use efficiency of SS50 was the highest,it was 16.0% higher than RT,and its difference with others were significant;In whole year,the water use efficiency of SS50 was the highest,it was 12.7% higher than RT,but there was no significant difference between SS30,SS40 and SS50.Subsoiling improved economic efficiency,SS30 and SS40 had the most economic benefits,it was 16.6% and 14.8% higher than RT respectively.Therefore,the suitable deep depth of The Lime Concretion Black Soil is 30-40 cm. |
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