Study On The Changes Of Soil Quality And Productivity In Different Years Of Cultivated Land

Unutilized land development is an important way to solve the contradiction between people and land in China and to ensure food security.The whole country and all regions attach great importance to the development and utilization of unused land.The quality of the soil determines the intrinsic production capacity of the land,and the main physical and chemical properties of the soil are an important part of the soil quality.Paying attention to the problem of soil quality in newly cultivated land,and clarifying the evolution law of the main physical and chemical properties of newly cultivated soil,it is of great significance for guiding land development and rational use of land resources.Other grassland is the main development and utilization object of the low mountain hilly area of Taihang Mountain.It is the main target of land development and utilization.The thin soil layer is an important limiting factor for its development and utilization.The implementation of guest soil engineering has become an important means to solve this limiting factor.There is a large amount of loess parent material distribution in this area,which is the main source of the guest soil.To this end,this paper takes the typical land development project area of Tang County of Hebei Province as the research area,and takes the cultivated land with different development years as the research object.Through the combination of field investigation and indoor analysis,analyzing the soil quality changes of different development years(1,3,6,10,15 and 20 years)and different soil depths(0~20 cm and 20~40 cm),and aiming at rational land development and provide theoretical basis for guiding agricultural production.The main findings are as follows:(1)The variation laws of soil chemical and microbial indicators in different development years and different soil depths were analyzed.From the perspective of different development years,the content of organic matter,total nitrogen,alkali nitrogen and total phosphorus in 0~20 cm soil layer was significantly positively correlated with the development period.There was a significant positive correlation between organic matter and total nitrogen content in the 20~40 cm soil layer.The total potassium was significantly negatively correlated with the development years in both soil layers.The correlation between pH and other nutrient indicators and development years was not significant.The results of different soil depths in the same development period indicate that the organic matter,total nitrogen,alkali nitrogen,total phosphorus and available phosphorus in 0~20 cm soil layer are higher than 20~40 cm.The difference between total potassium and available potassium in the two soil layers is small.The annual average rate of change of each indicator indicates that the organic matter and total nitrogen reached a relatively stable state after about 10 years of development,and the annual average rate of change of pH and total phosphorus was small.Soil microbial biomass carbon showed some volatility in 0~20 cm soil layer,and gradually decreased in 20~40 cm soil layer.Soil microbial biomass nitrogen showed a decreasing trend in both soil layers.(2)The variation laws of soil physical indexes of different development years and different soil depths were analyzed.There was no significant correlation between bulk density,total soil porosity,field water holding capacity,and soil mechanical composition and development years.Compared with the soil source,the bulk density of 0~20 cm and 20~40 cm soil layers increased after the development of cultivated land,and the total porosity and field water holding capacity decreased.The number of large aggregates in the soil increases,the number of microaggregates decreases,and the mechanical stability and water stability of soil aggregates increase.The soil texture is loam.Between different soil layers,the 0~20 cm soil layer has a bulk density of less than 20~40 cm,the total porosity is higher than 20~40 cm,and the field water holding capacity and water stable aggregate content are higher than 20~40cm.The cosmid,powder and sand have no obvious distribution between the two soil layers.(3)A comprehensive evaluation of soil productivity and soil quality was conducted.Both maize yield and aboveground biomass showed a trend of increasing first and then decreasing with the development years.The lowest yield of maize in the development of 3 years was 4505.68 kg/hm~2,and the highest yield of maize in the development of 10 years was 7172.51 kg/hm~2.Correlation analysis showed that the main influencing factors of maize yield and aboveground biomass were nutrient factors.The sensitivity analysis of indicators showed that organic matter,total nitrogen,alkali nitrogen,available phosphorus,available potassium,water-stable aggregates and soil microbial biomass nitrogen were sensitive to time changes.The soil quality index SQI of 0~20 cm and 20~40 cm soil layer first increased and then stabilized.The correlation analysis between SQI and yield showed that the constructed soil quality assessment model can better reflect the soil productivity level.In summary,the evolution characteristics of soil physical,chemical and biological properties and soil productivity of newly developed cultivated land were analyzed from different development years and different soil depths.Based on the sensitivity of soil quality indicators to time changes,the soil quality assessment model is constructed to comprehensively evaluate soil quality,which has important reference significance for guiding land development and agricultural production.