Nutrient variations from swine manure to agricultural land

OBJECTIVE: Swine manure in Korea is separated into solid and liquid phases which are composted separately and then applied on land. The nutrient accumulation in soil has been a big issue in Korea but the basic investigation about nutrient input on arable land has not been achieved in detail. Within the nutrient production from livestock at the national level, most values are calculated by multiplication of the number of animals with the excreta unit per animal. However, the actual amount of nutrients from swine manure may be totally different with the nutrients applied to soil since livestock breeding systems are not the same with each country. METHODS: This study investigated 15 farms producing solid compost and 14 farms producing liquid compost. Composting for solid phase used the Turning+Aeration (TA) or Turning (T) only methods, while liquid phase aeration composting was achieved by continuous (CA), intermittent (IA), or no aeration (NA). Three scenarios were constructed for investigating solid compost: i) farm investigation, ii) reference study, and iii) theoretical P changes (ΔP = 0), whereas an experiment for water evaporation was conducted for analyzing liquid compost. RESULTS: In farm investigation, weight loss rates of 62% and 63% were obtained for TA and T, respectively, while evaporation rates for liquid compost were 8.75, 7.27, and 5.14 L/m(2)·d for CA, IA, and NA, respectively. Farm investigation provided with the combined nutrient load (solid+liquid) of VS, N, and P of 117.6, 7.2, and 2.7 kg/head·yr. Nutrient load calculated from farm investigation is about two times higher than the calculated with reference documents. CONCLUSION: The nutrient loading coefficients from one swine (solid+liquid) were (volatile solids, 0.79; nitrogen, 0.53; phosphorus, 0.71) with nutrient loss of 21%, 47%, and 29%, respectively. The nutrient count from livestock manure using the excretion unit has probably been overestimated without consideration of the nutrient loss.