Differences in Soil Chemistry and Microbial Community between the Upland Converted from Paddy and the Existing Soybean Upland

Abstract

Change in land use can alter soil chemical properties and microbial community composition that are greatlyassociated with the soil quality and health. In South Korea, large numbers of paddy areas have recentlyconverted to upland fields, and various types of land management are conducting to improve the soil fertilityand productivity. However, lack of studies have been reported to seek out proper soil management in uplandsconverted from paddies so far, and also there are few studies about soil microbial community and itsrelationship with soil properties in the agricultural lands. This study aimed to investigate differences in soilchemistry and microbial community structure between upland converted from paddy and existing soybeanupland and to evaluate their changes according to the cultivation periods following the land use conversion. As a result, the soil chemistry and microbial community composition varied significantly with various fertilizertreatments including non-fertilizer (NF), inorganic fertilizer (NPK), and a mixture of NPK and compost(NPKC). Additionally, variations in the chemical and biological parameters were influenced by the period offarming practices following the land use conversion. Overall, the major soil factors related to the change insoil chemistry by different fertilizer treatments; in particular, organic matter (OM), available phosphate (Av. P2O5), and exchangeable K (Ex. K). It is likely that such differences in the chemical parameters were closelylinked to the change in soil redox condition after the conversion to uplands. This may affect the formation ofsoil microbial community structure, directly or indirectly, throughout the whole treatments of this study. Theindices of abundance/richness including abundance-based coverage estimator (ACE) and Chao and alphadiversity including Shannon and non-parametric Shannon (Np-Shannon) were in the order NPCK > NPK > NF,consistently. Also, the microbial community structure at phylum level was observed in the order of Proteobacteria> Acidobacteria > Actinobacteria > Chloroflexi > Verrucomicrobia > Planctomycetes > Firmicutesin the soils of this study. Among the bacterial phyla, Acidobacteria and Bacteroidetes that are aerobic andplay a key role in nutrient cycling were found to increase their population as the cultivation period increasedafter the conversion of land use. However, despite the increase in such beneficial bacteria abundance relatedto nutrient cycling through the soil management for 3 years, it seems that the low availability of P in soils of alltreatments and severe climatic conditions adversely affected the soybean yield. Therefore, in order to maximizethe soil fertility and productivity after conversion from paddies to uplands, it is important to find out proper soilmanagement approaches for each cropland. Also, such land management should be continuously implementedby identifying environmental factors and microbial community structures that are largely related to soilquality and health improvement.