Effects Of Tillage Methods And Straw Returning On The Fertility Of Shajiang Black Soil And The Winter Wheat Growth

Shajiang black soil has relatively high clay content,and it is mainly composed of 2:1type montmorillonites.Due to the property of shrinkage and swelling,Shajiang black soil has low available water capacity,nutrition content,and fertility level,which is a kind of typical middle and low yield soil in China.Straw returning is an important measure to improve soil organic matter and soil structure.Different tillage measures will directly affect soil and surface layer structure.Based on the typical rainfed farmland soil,Shajiang black soil as the research object,based on long-term field experiment to study the different tillage and straw counters-field modes of soil available nutrient,soil bulk density and the change characteristics of aggregate,and its effects on winter wheat yield and nutrient availability.Field trials were set with rotary tillage(R),deep tillage(D)and no-tillage(N).Different tillage practices were designed straw returning to fields with NPK(SF),NPK balance application(F)and control(CK)treaments.The research results and progress are as follows:1.The organic matter content in surface layer(0?20 cm)of typical Shajiang black soil is about 23.80 g/kg.The alkali-hydrolyzed nitrogen,available phosphorus and potassium were 63.66?71.48,9.29?14.26,182.78?242.70 mg/kg.For this type of soil improvement needs,the content of organic matter,alkali-hydrolyzed nitrogen and available phosphorus are low,especially the last one is low,and the content of available potassium is high.2.SF treatment,especially under different tillage modes,had significantly highercontribution to alkali-hydrolyzed Nitrogen and available potassium than the balanced application of F treatment.Under no-tillage and straw returning treatment,it had little contribution to soil available nutrients due to its difficulty in decay.The thickness of surface layer and the content of available nutrients in surface layer(0?20 cm)were increased by deep tillage treatment,but the content in surface layer(0?10 cm)was significantly lower than that of rotary and no-tillage treatment.Under no-tillage treatment,available nutrients were mainly concentrated in the surface soil.3.The bulk density of typical Shajiang black soil is about 1.25g/cm~3.It has obvious intergranular condensation and developed pore distribution.Under the action of freeze-thaw alternations,the soil in spring is more dispersed and the bulk density of soil is lower.From jointing stage to maturity stage of winter wheat,the soil showed obvious cohesiveness.With the decrease of water-stable aggregate content(<0.25 mm),soil bulk density showed an overall trend of increasing.4.Straw returning and NPK balanced application reduced the content of water stableaggregates(<0.25 mm),and the soil bulk density also showed a downward trend.With the participation of organic matter,the water-stable large aggregates is helpful to alleviate the soil adhesion barrier factors caused by the cohesion of soil clay particles.In different tillage,the soil bulk density of deep tillage was slightly higher than rotary tillage because the bottom soil was compacted.5.The contents of nitrogen and potassium in winter wheat reached the highest value atthe jointing stage;The phosphorus content reached the maximum value at the wheat heading stage,which obviously lagged behind the accumulation of nitrogen and potassium in the crops.Under different treatments,the contents of nitrogen and potassium in crops,as well as the phosphorus in crops under rotation and no-tillage showed the same changes as that SF>F>CK treatment.The content of available potassium in soil was higher and the effect on its accumulation in grains was not obvious.The available phosphorus content(0?10 cm)under deep tillage treatment is low,under the condition of high crop yield,the accumulation in winter wheat was inhibited.6.Under rotary and deep tillage,there was no difference in SF and F treatment of straw yield,but grain yield was significantly higher than that of the latter.In the mode of straw returning to the field,the increase of nutrients contributed to the improvement of crop yield,but in the no-till mode,the improvement of crop yield was not obvious due to the difficulty of straw decomposing.The deep tillage nutrient content of the surface layer(0?10 cm)was lower than rotary tillage,but there was no significant difference in crop yield.Under the deep tillage mode,the crop yield was also affected by the improvement of the soil structure in the tilled layer.As a conclusion:compared with rotation,deep tillage can increase surface layer thickness,improve soil structure,promote straw decomposition and nutrient release,which is good for soil clay weight barrier factor reduction and yield increase in this type of soil.No-tillage treatment improves the nutrient content of the surface soil,but the straw stalk rot solution is difficult.Evene straw returned,the soil compaction can not be effectively improved and the crop yield was restricted.