Submitted to: American Forage and Grassland Council Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/15/2003
Publication Date: 4/29/2003
Citation: Schmidt, K.M., Russelle, M.P., Sheaffer, C.C., Christians, C.J. 2003. Risks from high manure application before pasture restoration. American Forage and Grassland Council Proceedings. p. 233-237. Interpretive Summary: Livestock manure has the potential to be a beneficial resource to farmers when applied to land that will be seeded with a mixture of perennial grasses and legumes. The benefits to the land and plants include increased soil organic matter, a readily available supply of essential plant nutrients, such as nitrogen, phosphorus, potassium, and micronutrients, and added moisture-holding capacity. The benefits to the dairy farmer include reduced need for commercial fertilizer and an economical way to utilize the manure. However to reap these benefits, farmers must be circumspect in their management practices. The manure is best incorporated into the soil to prevent the loss of nitrogen gases to the atmosphere, loss of nutrients in runoff, and limit the odors associated with manure. Excessive application rates of manure pose serious risks, including buildup of nitrate to toxic levels in forage, imbalances of nutrient supply that can cause livestock disorders such as grass tetany, and, if the nutrients are in such high supply that forages cannot absorb them, runoff of nutrients may occur, polluting waterways. This research was conducted on a site where too much manure had been applied and showed that serious economic consequences can occur even when care is taken during grazing. When managed properly, incorporating livestock manure before planting pastures can produce cost savings for farmers and even result in enhanced environmental quality.
Technical Abstract: Livestock producers are faced with difficulties in applying manure uniformly, and occasionally may be tempted to apply excessive rates in areas adjacent to farmsteads. We studied the effect of excessive manure application to a silt loam soil on a 3-acre field that was subsequently seeded to a pasture mix. Large losses of soil nitrate occurred, presumably by leaching. Grass tetany was a risk for livestock grazing grasses in the mixture. The more serious problem was forage nitrate. Three ewes died of nitrate poisoning after selective grazing during the second growing season after manure application. Although forage nitrate concentrations had fallen to an average of 1,400 ppm, some weeds contained more than 8,000 ppm nitrate-N. Manure 'disposal' can harm the environment, forage quality, and livestock health. These results also may apply to potential problems on out-wintering sites, where excessive manure accumulates.