Effects Of Tillage And Fertilization On Composition Of Organic Carbon Pool In Dark Loessial Soil Of Weibei Hiagland

Weibei highland is a typical rainfed agricultural area of the Loess Plateau.As an important grain production base in Shaanxi province,the soil is classified as dark loessial soil and winter wheat is one of the main food crops.The traditional tillage method is mainly ploughing,which causes severe disturbance to soil,resulted in a series of problems such as soil erosion,serious loss of soil organic carbon due to mineralization and degradation of soil quality.In recent decades,no-tillage,subsoiling and other tillage methods have been applied in the area widely,but the effects of different tillage measures on soil properties,especially soil organic carbon,need to be further studied.This paper is based on a field experiment with different tillage measures in dark loessial soil on Weibei highland?started in 2007,samples were taken in 2016?,and the experiment was conducted with six tillage measures under straw returning and 3 fertilizer levels?balanced fertilization,conventional fertilization,and low fertilization treatment?in winter wheat single cropping system.The tillage measures included no-tillage-subsoiling?NS?,subsoiling-conventionaltillage?SC?,conventional tillage-no-tillage?CN?,no-tillage?NN?,subsoiling?SS?,conventional tillage?CC?.This study investigated the effects of tillage methods and fertilization on soil organic carbon storage and wheat yield,carbon sequestration rate,the content of organic carbon fractions and the distribution ratio.With a view to understanding the relationship between soil organic carbon storage and tillage measures,this paper provided a theoretical basis for the optimization of tillage measures in Weibei highland in Shaanxi Province.The results were as follows:?1?The effect of tillage measures on soil organic carbon.Under the condition of straw returning,the carbon sequestration rate of all treatments of0⁵0 cm soil layer was positive,which showed that the organic carbon was net fixed.The organic carbon content,storage and carbon sequestration rate of 0⁵0 cm soil layer were higher under balanced fertilization than low fat and conventional fertilization.Under 3 kinds of fertilization,Compared with conventional tillage?CC?,the soil organic carbon storage and carbon sequestration rate of rotational tillage?NS,SC and CN?and SS treatment were increased,and the maximum increment was found to be in the treatment of NS under balanced fertilization,respectively 50.63 t.hm^-22 and 153.69 kg.hm^-2.a^-1.From different soil layer,Under 3 kinds of fertilization,Compared with conventional tillage?CC?,the measures of NN mainly increased the SOC content and carbon sequestration rate of 0¹0 cm soil layer by 29.92%⁴6.84%and 239.71%²9.92%respectively.The measures of rotational tillage?NS,SC and CN?and SS not only improved the soil SOC content and carbon sequestration rate of 0¹0 cm soil layer,also improved the soil SOC content and carbon sequestration rate in the soil layer below 10 cm.?2?Effects of tillage measures on soil organic carbon fractions.Compared with conventional tillage?CC?,the measures of rotational tillage?NS,SC and CN?,NN and SS increased the content of soil active organic carbon,and soil easy oxidized organic carbon?EOC?,particulate organic carbon?POC?,microbial biomass carbon?MBC?,water-soluble organic carbon?WSOC?were increased by 4.82%²1.74%,9.37%³5.58%and 9.37%⁴0.35%and 5.04%³0.64%in 0¹0 cm soil layer,respectively;and the measures of rotational tillage and SS also increased soil active organic carbon accounted for the proportion of the total organic carbon.From different soil layer,Under straw returning and3 kinds of fertilization,Compared with conventional tillage?CC?,the measures of rotational tillage,NN and SS mainly increased the content of soil active organic carbon in 0¹0 cm soil layer,in>10 cm soil,rotational tillage,NN and SS treatments changed the active organic carbon content with different level,and NN was basically characterized by reducing effect,rotational tillage and SS treatments pEOCessing performance is increased.Under 3 kinds of fertilization,Compared with conventional tillage?CC?,the content of hardly oxidized carbon?HOC?and minberal-bound organic carbon?MOC?were increased by the measures of rotational tillage?NS,SC and CN?,NN and SS in 0⁵0cm soil layer,the maximum increment was found to be in the treatment of NS,by10.39%¹8.23%for HOC and by 13.69%¹8.23%for MOC,respectively.From different soil layers,compared with conventional tillage,the resistant organic carbon content of rotational tillage?NS,SC and CN?,NN and SS treatments were increased significantly in the 0-10cm soil layer,while there was no significant change in the soil layer below 10cm.?3?Effect of tillage measures on soil carbon pool management index?CPMI?.Effect of tillage and fertilization on soil carbon pool management index and their interaction were significant.From different soil layer,Under straw returning and 3 kinds of fertilization,Compared with conventional tillage?CC?,the measures of rotational tillage?NS,SC and CN?,NN and SS mainly increased CPMI in 0¹0 cm soil layer;in>10 cm soil,the CPMI of rotational tillage were characterized by increasing trend,NN treatment was basically characterized by reducing effect on CPMI,and SS increased CPMI in 35⁵0 cm soil layer.In0⁵0 cm soil layer,compared with conventional tillage?CC?,the CPMI of NN treatment had no obvious change,but rotational tillage and SS treatment increased CPMI,and the CPMI of NS treatment was highest.?4?Effect of tillage measures on wheat yield and the apparent humification coefficient of straw.The wheat biomass and yield were higher under balanced fertilization than low fat and conventional fertilization.Compared with conventional tillage?CC?,the wheat biomass and yield of rotational tillage?NS,SC and CN?and SS treatment were increased,NN treatment had no obvious change,and the maximum increment was found to be in the treatment of NS,by 8.97%¹3.63%for wheat biomass and by 12.17%⁸.97%for wheat yield,respectively.Under straw returning and 3 kinds of fertilization,the average apparent humification coefficient of straw in conventional tillage?CC?treatment was 10.12%,which was lower than that in the treatments of NN,SS and rotational tillage?NS,SC and CN?.Compared with conventional tillage,the measure of NS increased the sharpest,88.68%¹23.55%.In general,based on soil carbon pool and wheat yield,the tillage of NS under balanced fertilization was the most suitable measure for Weibei highland.