Difference in Biochemical Properties of Soils with Different Periods of Agricultural Practice after Conversion from Paddies to Uplands

Abstract

The intrinsic characteristics of soil can be altered by purpose of land use and its history, which would determinethe quality and health of the soil. In South Korea, along with the trend of decreasing agricultural landarea, land use conversion from paddies to uplands is being promoted to alleviate the oversupply of rice and toimprove the self-sufficiency rate of field crops. So far, in order to increase the productivity of crops after landuse conversion, various types of soil management have been applied, focusing mostly on chemical propertiesrelated to soil fertility rather than biological properties related to soil health. This study was conducted tocompare the difference in soil biochemistry of uplands with different periods of land use conversion frompaddies, and to investigate the interrelationship between these soil characteristics. In general, there weresignificant differences in chemical parameters of soils according to the period of soybean cultivation (2, 4, and10 years) after land use conversion of paddy fields. In Andong region, soil pH, organic matter (OM), totalnitrogen (T-N), available phosphate (Av. P), and exchangeable potassium (Ex. K) increased with increase inthe period of the land use conversion. Similarly, pH, Av. P, Ex. K, Ex. Ca, Ex. Mg and Org. P were the highestin the 10-year soybean growing uplands. Like the soil chemistry, soil microbial enzyme activities includingdehydrogenase (DHA), β-glucosidase (BG), alkaline phosphatase (ALP), and arylsulfatase (AS) differed bythe period of agricultural practices since the land use conversion but varying with study areas. Principlecomponent analysis (PCA) showed clear separations of the upland soils with different periods of farmingsince land use conversion that is highly influenced by soil OM and pH as well as BG and ALP in both areas. With comprehensive interpretation of all results in this study, we predicted that, in both areas, applications ofinorganic and organic fertilizers have been continuously performed, thereby improving the soil productivityof uplands converted from paddies following the land use conversion. As such, improved quality of the soilsby the land managements could result in a positive effect on the soil health, by enhancing the overall microbialabundance as well as stimulating their functions such as nutrient cycling.