Manure is a valuable source of plant nutrients but also a potential pollutant. Manure has the potential to negatively affect surface water quality (from pathogens, phosphorus, ammonia, and organic matter); ground water quality (from nitrate); soil quality (from soluble salts, copper, arsenic, and zinc); and air quality (from odors, dust, pests, and aerial pathogens).
In addition to manures, commercial fertilizers, other waste products, plant residues, and green manures applied to the land can contribute to environmental problems due to excess nutrients, both at the site of application and in surface and ground waters. Nutrients from all sources need to be accounted for and managed in any production system to sustain our farms and protect the environment. Problems can arise hundreds of miles from these sources. For instance, excessive use of nitrogen fertilizers in the Mississippi and Missouri river basins is thought to be the major cause of the hypoxia problem in the Gulf of Mexico. Although nitrogen and phosphorus are the major environmental offenders, poorly managed fertilizers, wastes, and organic materials can lead to a buildup of nutrients as salts, and the release of toxic compounds such as sulfides and sulfites, boron and selenium salts, and heavy metals. Non-nutrients, such as arsenic, lead, and mercury, can also come from fertilizers and manures.
Animal manures can also be a source of pathogens, antibiotics, and other bioactive compounds such as endocrine disruptors (estrogens).
For centuries, animal manure has been recognized as an excellent source of plant nutrients and as a soil "builder" because of its contributions to improving soil quality. When compared to more conventional fertilizer, manure properly applied to land, provides environmental benefits, including: reduced nitrate leaching; reduced soil erosion and runoff; increased soil carbon and reduced atmospheric carbon levels; reduced energy demands for nitrogen and phosphorus fertilizers, which is a limited resource; and improved productivity of cropping systems.
Manure contains most elements required for plant growth including nitrogen (N), phosphorus (P), potassium (K), and micro-nutrients. But, it is manure’s unique combination of these nutrients with organic carbon that provides its value to crop production and the environment. First, manure (N) is more stable than (N) applied as a commercial fertilizer. A significant fraction of manure (N) is stored in an organic form that is slowly released as soils warm. Commercial fertilizer (N) is applied in either a nitrate or an ammonium (easily converted to nitrate) form. Nitrate (N) is very soluble and mobile and, early in the growing season, it contributes to leaching during excess precipitation or irrigation. Manure's slow transformation to crop available forms is better timed to crop (N) needs, resulting in less leaching potential.
In addition, some manure (N) is released very slowly, often not becoming available until the second or third year after application, thus providing long term benefits. High soil organic matter content is considered a measure of a productive soil. Most nutrients that enter the plant root zone are involved in a range of microbial processes during their conversion to plant-available forms. Manure’s organic carbon provides the energy source for the active, healthy, soil microbial environment that both stabilizes nutrient sources and makes those nutrients available to crops. Manure has the ability to reverse or return soil organics backto their original level before cultivation. From a nutrient perspective, manure contributes to improved soil structure, water infiltration and greater water-holding capacity. Increased manure application rates produced greater reductions in soil erosion and runoff. During years when manure is not applied, a residual benefit of past manure application is measurable.
Historically animal manures have been handled as a solid, and were either deposited directly to pasture, (by the animals) or collected (along with the bedding used in the animal shelter) and applied to land as a crop nutrient. As the number of animals on farms has increased, the need for more efficient methods of manure management has also developed.
Manure from animals is a very wet, bulky material, containing as much as 90% water. Of the 10% that is dry matter, much of it is carbon. The manure handling system can impact the characteristics of the animal waste stream. Water-based waste management systems may have a liquid stream with greater than 98% moisture, while manure scraped from open lots can contain a very high percentage of soil. As a result, the nutrient content of the manure is a very small portion of the weight/volume. Hauling nutrients to cropland in the form of manure can get very expensive compared to hauling the same amount of nitrogen or phosphorus in the form of commercial fertilize.
PureAg has developed a methodology to liquefy and biodegrade the nutrient load and deliver the process water to a pivot. The combination of aeration and inoculants can liquefy a lagoon in a mater of days, and can completely remove the winter storage component most growers and dairyman are facing. The bio availability of the nutrients and the ease of handling make this process very attractive to a cost conscious farmer.
These treatment techniques include nutrient reduction (primarily nitrogen and phosphorus), odor reduction, volume reduction, and adding value to the manure. There may be additional benefits to these manure treatment technologies beyond the primary treatment goals such as the reduction of emissions of particulate matter or greenhouse gases.
We would love to explore your manure management issues and design you a solution. Sample water quality results and references are available on request.