Effects Of Different Tillage Patterns On Soil Organic Carbon And Crop Yield In Degraded Black Land

As one of the largest grain producing areas in China,the black land in Northeast China is an important part of the agricultural development in Northeast China.In recent years,due to a series of problems brought by the traditional farming mode,the soil nutrient is much lower than before,the quality of the black land farmland is reduced,and the crop yield is decreasing year by year.In order to solve this problem,conservation tillage mode with straw mulching as the main means has been carried out in various regions.This paper takes different farming modes as the starting point to explore the soil organic matter and crop yield in the study area of Changtu County,Tieling City.First,the change of land use types in Changtu County on the time scale was interpreted and analyzed.The results showed that the proportion of cultivated land in Changtu County was the highest among all land use types,but the proportion of urban land expanded by 35.57%in the 38 year time scale.The area of dry land,paddy field,forest land,grassland and water area showed a downward trend year by year.This study designed a positioning experiment in the Changtu demonstration area.There are five kinds of experimental designs:conventional tillage(straw not returning to the field),large two-ratio air-tillage(straw returning to the field),large two-ratio air-tillage(straw returning to the field),small two-ratio air-tillage(straw returning to the field),small two-ratio air-tillage(straw returning to the field),and small two-ratio air-tillage(straw returning to the field).The impact of each tillage mode on soil physical and chemical properties and crop yield was analyzed,DNDC model is also used to predict and analyze soil organic carbon content and crop yield in the next 50 years.Due to the large problems of farmers in fertilizer application and cultivation mode in Changtu County,the values of soil nutrients have been reduced.Through field experiments in the 100000 mu watershed of the degraded brown soil demonstration area in Changtu County,50 topsoil samples were sampled for physical and chemical index tests.The results of soil organic matter and total nutrients showed that the average content of soil organic matter was 16.76g/kg;The average content of total nitrogen in soil is 0.10%;The average content of total phosphorus in soil is 0.05%;The average content of total potassium in soil is 2.39%.The results of soil available nutrients showed that the average content of soil available phosphorus was 25.9 mg/kg;The average content of available potassium in soil is 128mg/kg;The average content of soil alkali-hydrolyzable nitrogen is109.7mg/kg;The average soil p H is 5.32;The average soil bulk density is 1.45g/cm~3;The average soil moisture content is 22.91%;The average soil conductivity is 59.17μs/cm;The average thickness of black soil layer is 23cm.The results of autumn crop yield showed that the minimum crop yield was 471 kg/mu,the maximum was1142 kg/mu,and the average was 753 kg/mu.The results of seedling investigation showed that the maize seedling emergence rate of the four straw returning conservation tillage modes was significantly improved compared with the conventional tillage treatment,with the increase rate between 5%and 10%.The seedling emergence rate of the small two ratio empty no-tillage maize was the highest,followed by the big two ratio empty no-tillage and strip tillage.The results of corn yield data showed that the corn yield of the four straw returning conservation tillage modes was significantly improved compared with the conventional tillage treatment,with an increase rate of 15%-29%.The conservation tillage mode has achieved remarkable results.Compared with the conventional tillage mode,its seedling rate has increased,and its yield has increased,and the two-ratio air-tillage technology mode has the best effect.The organic carbon content and crop yield in the next 50 years are predicted by DNDC model,and the research objects are conventional tillage(N),large two-ratio empty strip tillage(SS)and large two-ratio empty no-tillage(SN)tillage models.The results showed that through the root mean square error and the correlation analysis of relative coefficients,the results could better reflect the values of soil organic carbon content and crop yield in the current study area.In the next 50 years,soil organic carbon under conventional tillage(N)mode will decrease year by year;The soil organic carbon showed an upward trend under the big two ratio empty strip tillage(SS)and big two ratio empty no-tillage(SN)models,increasing to 26.34%and22.13%respectively.Returning straw to the field can effectively increase the concentration of soil organic carbon,and has a positive impact on the stability of corn crop yield.In the next 50 years,the crop yield under conventional tillage(N)mode will show a downward trend,from 780 kg/mu at the beginning to 514.3 kg/mu,with an overall decrease of 34.06%.The crop yields under the large two ratio empty strip tillage(SS)and large two ratio empty no-tillage(SN)modes both showed a trend of first decreasing and then increasing,with the decline ranges of 8.73%and10.66%,respectively.Returning straw to the field can effectively improve the yield of crops.To sum up,compared with the traditional conventional tillage mode,the conservation tillage mode of returning straw to the field plays an effective role in increasing soil organic carbon content and crop yield,and is a long-term practical farmland management mode.