Liquid swine manure fertilizer (LSM) replenishes micronutrients into cropland but also contributes heavy metals that accumulate and may reach phytotoxic levels. This study uses EPA soil survey methods and atomic absorption spectroscopy to analyze well-drained mildly acidic soil from a LSM-fertilized Missouri agricultural field and its surrounding non-tilled grassland for EDTA-extractable copper and zinc. Compared to a control area, the amount of copper and zinc in the field increased from 2.6 ppm to 6.1 ppm, and 4.9 ppm to 9.8 ppm respectively, over a 16 year period. This observed heavy metal buildup is significant but below phytotoxic levels. The cropland perimeter that immediately surrounds the area shows intermediate values of 3.3 ppm and 7.7 ppm Cu and Zn, respectively. This study indicates that disposal of LSM as fertilizer is a sustainable and beneficial practice in this type of setting.
