Characterization of dairy slurry in Southern Chile farms

In this study 50 slurry samples were collected from commercial dairy farms located in the South of Chile during 1995-1997. Samples were analyzed for dry matter, pH, organic matter, available and total macro nutrients (nitrogen, phosphorus, potassium, calcium, magnesium and sodium), available and total micronutrients (zinc, iron, manganese and copper) and total aluminum. Results showed that the dry matter content in dairy effluents was low, with 62% of the samples being < 4% DM. This reflected the large volumes of water that the storage received. A great variation in nutrient content was observed in the analyzed samples, probably reflecting differences in feeding regimes, use of wash water, rainfall and age of slurry at the time of sampling. In general, the concentration of macro and micronutrients was low. In the present study, the dry matter in the slurry proved to be a good indicator of some nutrients in the samples analyzed. Positive correlations (p < 0.001) were obtained between dry matter content and total phosphorus (r(2) = 89%), total calcium (r(2) = 87%), total magnesium (r(2) = 82%), available phosphorus (r(2) = 75%), ammonium nitrogen (r(2) = 68%), total potassium (r(2) = 64%), available potassium (r(2) = 60%), total nitrogen (r(2) = 55%), total zinc (r(2) = 74%), total manganese (r(2) = 64%) and total iron (r(2) = 62%). Data from this study could be used as a guideline to estimate nutrient contribution from dairy slurry when applied to farmland.