The most nutrient-enriched runoff occurs when manure is surface applied to frozen or sloping land just prior to a major runoff event. 23 Various manure application methods affect nutrient runoff. Surface applied manures undergo less rapid decomposition and therefore may contain a higher concentration of contaminants. Manure incorporation will be more likely to improve soil physical condition along with decreasing runoff volume and erosion. Odor can also be an occasional problem.
Anaerobic conditions can produce odorous and toxic gases.
Thus safety precautions are required for those working around storage pits, especially during the agitation of liquid manure and under conditions of poor ventilation. 24 Odors from land application of manure under certain circumstances can produce objectionable smells. Complaints occur more frequently with land application of manures than occur as a result of odors emanating from buildings or manure storage. 25 Incorporating manure into the soil at the time of application significantly decreases odor and NH 3 emission. Although phosphorus and nitrogen are naturally occurring in surface waters and are a necessary part of aquatic ecosystems, excessive amounts of these nutrients can result in excessive aquatic plant growth and a depletion of oxygen.