This lost nitrogen is not available for plant growth, and has been identified as a possible air quality contaminant contributing to acid rain. Manure solids spread on frozen or snow-covered soil have a high potential for runoff and resulting pollution. If manure is surface-spread on long slopes or areas with high erosion potential, strip cropping, diversions and other conservation practices can reduce runoff, nutrient loss and pollution. Manure should not be surface applied to soil near wells, springs, sinkholes, terrace tile inlets, wetlands, or on slopes adjacent to streams, rivers or lakes. In Missouri, cool-season grasses such as fescue are commonly used as manure utilization areas.
Manure is usually surface-applied without incorporation.
While this practice does not necessarily maximize nutrient conservation because of volatilization, pollution potential is no greater than with practices involving incorporation as long as manure is applied at the proper rate and soil conditions. However, runoff from a rainfall event immediately following surface application can transport nutrients from the field into surface waters. Subsurface application Water pollution potential can be decreased, and the amount of manure nitrogen available to plants can be increased, by working manure into the soil either by tillage or by subsurface injection. A soaking rain with no runoff has approximately the same effect as incorporating manure. Similarly, irrigation of lagoon effluent with no runoff is equivalent to incorporation.