Investigating Heavy Metal Levels of Greenhouse Soils Using Long-Term Livestock Manure

The use of eco-friendly compost, such as livestock manure, has increased due to the environmental pollution of chemical fertilizers. However, many farmers use livestock manure and inorganic fertilizer together, leading to excessive soil nutrients. Also, livestock manure includes heavy metals, so the long-term use of livestock manure could increase heavy metal levels, particularly in greenhouse soils. Therefore, this study aims to investigate heavy metal concentrations in greenhouse soils using long-term livestock manure. The soils were collected from 24 greenhouses applying livestock manure for 5 - 32 years in Gyeongnam province, Korea. The chemical characteristics and heavy metal concentrations of the soils were analyzed. As a result, soil pH, organic matter, available phosphorus, and exchangeable-Ca, Mg, and K of most soils were higher than the average values of greenhouses in Gyeongnam. The As, Cd, Cr, Cu, Ni, Pb, and Zn levels of the studied soils also exceeded Gyeongnam greenhouses’ average values. Moreover, Zn concentrations of three greenhouse soils were 394.4 mg kg-1, 305.3 mg kg-1, and 323.2 mg kg-1, which exceeded the Korean Zn threshold of 300 mg kg-1. The levels of Cu in these three soils showed higher values than in other soils, so the accumulation of Cu and Zn was mainly concerned with applying livestock manure. Thus, the soils using long-term livestock manure would be recommended for regular monitoring for food safety.Copper and zinc concentrations of 24 soils collected from greenhouse using manure compost (red line: Korean threshold value, blue line: average of Gyeongnam greenhouse soil).