Composition of Equine Manure as Influenced by Stall Management

A study was conducted to compare the composition of equine manure as removed from the stall, and bedding-free manure on six horse farms. The farms ranged from a pleasure horse stable with poorly managed stalls to an intensively managed stable for racehorses. The manure characteristics measured included: moisture content, total nitrogen, total ammoniacal nitrogen, nitrate nitrogen, organic nitrogen, total phosphorous (expressed as P2O5), total potassium (expressed as K2O), calcium, magnesium, sulfur, zinc, copper, manganese, iron, total carbon, electrical conductivity (index of soluble salts), and pH. Statistical analysis indicated that stall management had a significant impact on the dry basis concentrations of all plant nutrients, carbon, organic matter, pH, and EC. It was also determined that the C:N of stall manure ranged from 23.4:1 to 48.5:1 depending on the amount of bedding used and daily management. The C:N value of equine manure was used as an indicator of the level of stall management (high, medium, low). It was determined that the concentrations of nitrogen, phosphorous, calcium, magnesium, zinc, copper, and sodium were negatively correlated with the C:N of horse manure. Average EC measurements ranged from 1.86 to 3.46 mmhos/cm. A correlation analysis, that included all metals that could be in salt form, indicated that EC was significantly correlated with the K2O content but not with sodium, calcium, or magnesium. The high C:N values of horse manure indicated that composting may be a preferred method of treatment prior to land application. However, spreading equine manure based on the agronomic rate for P2O5 for a pasture and adding fertilizer nitrogen sufficient to reduce the C:N of applied manure to 10:1 to overcome induced nitrogen deficiency may provide another alternative.