Chemical Changes in Agricultural Soils of Korea: Data Review and Suggested Countermeasures

Abstract

The monitoring of chemical properties, including heavy metals, in soils is necessary if better management and remediation practices are to be established for polluted soils. The National Institute of Agricultural Science and Technology initiated a monitoring study that investigated fertility and heavy metal contents of the benchmarked soils. The study covered paddy soils, upland soils, and horticultural soils in the plastic film houses, and orchard soils throughout the Korea from 1990 to 1998. Likewise,4047 samples of paddy and 2534 samples of plastic house in 1999 and 2000 were analyzed through the Soil Environment Conservation Act. Soil chemical properties such as pH, organic matter, availablephosphate and extractable calcium, magnesium and potassium contents, and heavy metal contentssuch as cadmium, copper, lead, zinc, arsenic, mercury, and cobalt contents were analyzed. The studyshowed that the average contents of organic matter, available phosphate, and extractable potassiumrapidly increased in plastic house soils than in upland or paddy soils. Two kinds of fertilizer recommendation systems were established for the study: the standard levels by national soil average data for 77 crops and the recommendation by soil test for 70 crops. Standard nitrogen fertilizer application levels for cereal crops changed from 94 kg/ha in 1960s, 99 kg/ha in 1970s, 110 kg/ha in 1980s to 90 kg/ha in 1990s. The K₂O-fertilizer also changed from 67 kg/ha in 1960s, 76 kg/ha in 1970s, 92 kg/ha in 1980s, andonly 44 kg/ha in 1990s. In rice paddy fields, the average contents of Cd, Cu, Pb, and Zn in surface soils(0–15 cm depth) were 0.11 mg kg⁻¹(ranged from 0 to 1.01), 4.70 mg kg⁻¹(0–41.59), 4.84 mg kg⁻¹(0–66.44), and 4.47 mg kg⁻¹(0–96.70), respectively. In the uplands, the average contents of Cd, Cu, Pb, Zn,and As in surface soils (0–15 cm depth) were 0.135 mg kg⁻¹(ranged from 0 to 0.660), 2.77 mg kg⁻¹(0.07–78.24), 3.47 mg kg⁻¹(0–43.00), 10.70 mg kg⁻¹(0.30–65.10), and 0.57 mg kg⁻¹(0.21–2.90), respectively. In plastic film houses, the average contents of Cd, Cu, Pb, Zn, and As in surface soil were 0.12 mg kg⁻¹(ranging from 0 to 1.28), 4.82 mg kg⁻¹(0–46.50), 2.68 mg kg⁻¹(0–46.50), 31.19 mg kg⁻¹(0.19–252.0), and 0.36 mg kg⁻¹(0–4.98), respectively. In orchard fields, the averagecontents of Cd, Cu, Pb, Zn, As, and Hg in surface soils (0–20 cm depth) were 0.11 mg kg⁻¹(ranged from 0–0.49), 3.62 mg kg⁻¹(0.03–45.30), 2.30 mg kg⁻¹(0–27.80), 16.60 mg kg⁻¹(0.33–105.50),0.44 mg kg⁻¹(0–4.14), and 0.05 mg kg⁻¹(0.01–0.54), respectively. For polluted soils with over thewarning content levels of heavy metals, fine red earth application, land reconsolidation and soilamelioration such as lime, phosphate, organic manure, and submerging were recommended. For the countermeasure areas, cultivation of non-edible crops such as garden trees, flowers, and fiber crops; landreformation; and heavy application of finered earth (up to 30 cm) were strongly recommended. Landuse techniques should be changed to beharmonious with the environment to increase yield andincome. Soil function characteristics should betaken into account.