Characteristics of Acidity and Nutrient Changes in Red Soil After Conversion of Paddy Field to Dry Land and Vegetable Field
[Objective]The aim of this study was to analyze the characteristics of changes in soil acidity and nutrient content after the conversion of paddy fields with different parent material development into dryland and vegetable fields in Qiyang,a typical county in the red soil area,so as to provide a scientific basis for the rational use of land to prevent acidification in the area.[Method]18 sites were selected and collected from paddy fields and adjacent dryland and vegetable fields to analyze the changes of soil pH,exchangeable acid,exchangeable salt-based ions,organic matter,cation exchange,and nutrient content and their interrelationships.[Result]The pH of all the soils developed with alkaline parent material was significantly higher than that of the soils developed with acidic parent material.Soil pH decreased by 0.48 units after the conversion of acidic parent material developed paddy fields to vegetable fields;soil pH decreased by 0.74 and 0.53 units after the conversion of alkaline parent material developed paddy fields to drylands and vegetable fields,respectively.The bilinear model fit analysis showed that the soil exchangeable aluminum content increased rapidly when the soil pH was below 5.88,5.78 and 5.63 in the paddy field,dryland and vegetable field,respectively,and the increment of soil exchangeable aluminum content increased by 1.09,2.33 and 2.93 cmol(+)·kg-1 by one pH unit,respectively.Soil organic matter and total nitrogen content decreased by 11.06 and 0.42 g·kg-1,respectively,in the acidic matrices developed paddy fields converted to drylands,while no significant changes were observed in vegetable fields;soil organic matter and total nitrogen content decreased significantly in the alkaline matrices developed paddy fields converted to drylands and vegetable fields,by 13.88-17.28 and 0.57-0.71 g·kg-1,respectively.The total and effective phosphorus content of the soil increased significantly from 0.41-0.48 g·kg-1 and 26.79-28.69 mg·kg-1 after the conversion of the paddy field with alkaline parent material to dryland and vegetable field,respectively.Correlation analysis showed that soil pH was significantly and positively correlated with soil exchangeable calcium and magnesium,cation exchange,organic matter content and total nitrogen content(P＜0.01);soil exchangeable acid and aluminum were significantly correlated with effective phosphorus content(P＜0.05)and negative correlation(P＜0.01)with soil exchangeable calcium and magnesium,cation exchange,organic matter and total nitrogen.[Conclusion]Soil organic matter and total nitrogen content decreased significantly after the conversion of acidic and alkaline parent material developed paddy fields to drylands,while soil total phosphorus and effective phosphorus content tended to increase.Soil acidification was observed after the conversion of paddy fields to vegetable fields for acidic parent materials or to drylands and vegetable fields for alkaline parent materials;the increased nitrification and increased leaching of salt-based ions from paddy fields to drylands and vegetable fields might be one of the main reasons for soil acidification.
parent materialred soilconversion of paddy fields to dry land and vegetable fieldsoil aciditynutrient characteristics
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