Status and Change in Chemical Properties of Polytunnel Soil in Korea from 2000 to 2012

Chemical properties of agricultural soils in Korea have been investigated at four-year interval in order of paddy, polytunnel, upland, and orchard soils since 1999; polytunnel soils were investigated over the whole country in 2000, 2004, 2008, and 2012. Polytunnel soils were taken from the surface (0-15 cm) and subsurface (15-30 cm) at 2,651, 1,274, 1,374 and 1,374 sites in all provinces of South Korea. One hundred sampling sites located in more than 400 m altitude were additionally investigated in 2008 and 2012. Average of soil chemical properties in 2012 except Jeju province were 6.6 for pH, 3.2 dS m -1 for EC, 37 g kg -1 for organic matter (OM), 1,049 mg kg -1 for available (Avail.) phosphate, 1.58 cmolc kg -1 for exchangeable (Exch.) K, 10.6 cmolc kg -1 for Exch. Ca, and 3.3 cmolc kg -1 for Exch. Mg. Except pH, averages of all chemical properties exceeded the upper limit of optimal range. The median values except pH showed a lower value than the averages. The pH, OM and Exch. Ca had slightly increased from 6.3 to 6.6, from 34 to 37 g kg -1 , and from 7.7 in 2000 to 10.6 cmolc kg -1 in 2012, respectively. The order of sample ratios exceeding the optimal range were Avail. P2O5 (83%) > Exch. Ca (80%) > Exch. K (70%) > Exch. Mg (65%) > EC (55%) > OM (48%) > pH (29%) in 2012. The order of sample ratios below the optimal range was OM (25%) > Exch. K (25%) > pH (20%), Exch. Mg and Avail. P2O5 (9%) > Exch. Ca (6%) in 2012. The excessive proportion of pH, Exch. Ca, Exch. Mg and OM slightly increased, while the insufficient proportion of those decreased. Approximately 55% of polytunnel soils exceeding EC 2 dS m -1 was evaluated with salt accumulated soils having the risk of growth disorder of crops. Nutrient contents in polytunnel soils in Korea showed high level especially Avail. P₂O? and Exch. cations. Therefore, recommended fertilization based on soil testing or plant testing is needed for soil nutrient management.