Changes of Chemical Properties in Upland Soils in Korea

Soil testing is one of the major strategies for establishing sustainable agricultural practice as it analyzes nutrient contents of soil and determines the amount of nutrients required for crop growth. Soil testing for the field cultivating regional major crops in Korea has been conducting by National Academy of Agricultural Science (NAAS), provincial agricultural research & extension services and agriculture technology centers since 2000. 1,006,227 soil samples were analyzed and uploaded on Korean soil information system (http://soil.rda.go.kr) from 2003 to 2013. Soil pH has changed from 6.1 to 6.2. Organic matter (OM), available (Avail.) phosphate and exchangeable (Exch.) K have decreased from 24 to $23gkg^{-1}$, 541 to $399mgkg^{-1}$ and 0.90 to $0.72cmol_ckg^{-1}$ between 2003 and 2013, respectively. Especially, Exch. Ca contents decreased to $5.7cmol_ckg^{-1}$ in 2009 and increased to $6.2cmol_ckg^{-1}$ in 2013. Ratios of optimal ranges for cropping were 48% for pH, 22% for OM, 26% for Avail. phosphate, and 23, 16, 22% for Exch. K, Ca and Mg in 2013. Ratios of optimal ranges for pH increased and low ranges for OM, Avail. phosphate and Exch. K increased. Frequency distribution was 64% for pH 5.5~7.0, 65% for OM $10{\sim}30gkg^{-1}$, 48% for Avail. phosphate under $300mgkg^{-1}$ and 23, 29, 22% for Exch. K 0.2~0.6, Ca 4.0~6.0 and Mg $1.0{\sim}1.5cmol_ckg^{-1}$.