Status and Changes in Chemical Properties of Paddy Soil in Gyeonggi Province

Abstract

The chemical properties of paddy fields in Gyeonggi province were monitored every 4 years from 1999 to 2015 in order to provide basic information for soil fertility management of paddy fields. In 2015, the soil chemical properties of paddy fields were 5.9 in pH, <TEX>$23g\;kg^{-1}$</TEX> in organic matter (OM), and <TEX>$84mg\;kg^{-1}$</TEX> in available phosphate (Avail. <TEX>$P_2O_5$</TEX>). Exchangeable (Exch.) potassium (K), calcium (Ca) and magnesium (Mg) were 0.30, 5.1 and <TEX>$1.3cmol_ckg^{-1}$</TEX>, respectively, and available silicate (Avail. <TEX>$SiO_2$</TEX>) was <TEX>$129mg\;kg^{-1}$</TEX>. In the long-term analysis, the contents of Avail. <TEX>$SiO_2$</TEX>, Exch. Ca and pH of paddy soils showed increasing tendency. However, Avail. <TEX>$P_2O_5$</TEX> and Exch. K tended to decrease, and there were no significant changes in the contents of OM and Exch. Mg. Paddy soil within appropriate pH range increased from 44% in 1999 to 76% in 2003, 84% in 2007, 63% in 2011, and 80% in 2015. But soil within appropriate range of Exch. Ca tended to decrease, showing 36% in 1999, 42% in 2003, 38% in 2007, 37% in 2011 and 32% in 2015. In case of Avail. <TEX>$SiO_2$</TEX>, soil within appropriate range increased from 14% in 1999 to 17% in 2003, 18% in 2007, 16% in 2011, and 31% in 2015. As a result, paddy fields with less in nutrient level need to be more fertilized based on soil analysis. And the application of silicate fertilizer is strongly recommended to those of paddy fields in need. Also soil management such as the cultivation of green manure crop or application of rice straw will be necessary to increase the organic matter content of paddy soil.