In situ Rapid Estimation of Nutrients and Organic Matter in Swine Slurry by a Hydrometer

Swine waste is an important source of plant nutrients and organic matter thus it has been widely used as an organic fertilizer. However, careless spreading of livestock slurry increases the risks of soil, water, and air contamination. Therefore, in situ, rapid, simple, and inexpensive characterizations of slurry parameters are important for its proper use and to mitigate environmental risks. In this study we explored the significance of correlation models between physio-biochemical parameters and relative density (RD) of swine slurry. Slurry samples were collected from 46 commercial swine farms in South Korea and were characterized in terms of various physio-biochemical parameters and nutrients. Interestingly, considerable variations were observed in the analyzed parameters. However, linear correlations were observed between RD and total nitrogen (TN), ammonia nitrogen (NH3-N), total phosphorous (TP), total potassium (TK), iron, manganese, calcium, magnesium, sodium, total solids (TS), volatile solids (VS), total suspended solids (TSS), total dissolved solids (TDS), chemical oxygen demand (CODCr), biochemical oxygen demand (BOD5), and bacteria with coefficients of determination (R2) of 0.83, 0.61, 0.79, 0.67, 0.64, 0.64, 0.57, 0.55, 0.48, 0.90, 0.86, 0.65, 0.61, 0.67, 0.55, and 0.45, respectively. This method can provide a rapid (time 20-30 s) and inexpensive (a simple hydrometer costs ~US$2) tool for indicating changes in manure quality and thus can facilitate a good estimate of nutrients and organic matter when laboratory analyses are not readily available.