AgriLife Research economist: Manure provides higher (economic) returns than chemical fertilizers

June 28, 2010

AgriLife Research economist: Manure provides higher returns than chemical fertilizers

By: Kay Ledbetter, 806-677-5600
Contact(s): Dr. Seong Park, 940-552-9941, scpark@ag.tamu.edu

VERNON – No significant differences in corn yield were found between organic and chemical sources of nutrients, but a Texas AgriLife Research economist said manure generates higher economic returns than anhydrous ammonia.

Dr. Seong Park, AgriLife Research economist, recently had his research published in the Agronomy Journal. The work was from studies he conducted in the Oklahoma Panhandle while at Oklahoma State University and finalized while in his new position at Vernon.

The long-term experiment involved the use of pig and beef manure on irrigated corn fields, he said. The testing was conducted in part due to a rapid growth of animal population and density in that region, as well as the northern part of the Texas Panhandle.

Park said when swine manure, which is normally stored in open-air lagoon systems, is properly applied and the economics figured, the effluent can be used as manure with minimal environmental and nuisance concerns.

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The art and practice of composting is an ancient one – dating back thousands of years. The ancient Romans and Greeks deliberately piled animal manures and soil in such a way as to aid in decomposition. The Bible also speaks of it. The value of crushed bones, wool waste, wood ashes and lime is spoken of in old Arabic manuscripts. The Medieval church preserved the knowledge and composting continued through the Dark Ages, Renaissance and in the New World by the native Indian tribes and early European settlers.

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Composting: A Greenhouse Gas Mitigation Measure

Ton for ton, composting reduces GHG emissions from organics management over any other management option.

Compostable organics make up 30% of California's overall waste stream, contributing over 12 million tons annually to our state’s landfills. In landfills, this material undergoes anaerobic decomposition and produces significant quantities of methane, up to 80% of which is not captured by a landfill gas system. Composting, on the other hand, is a fundamentally aerobic process, and well managed compost facilities do not produce any methane. Composting offers an environmentally superior alternative to landfilliing organics that eliminates methane production, provides a series of http://www.cawrecycles.org/issues/food_composting">economic and environmental co-benefits, and has a substantial impact on greenhouse gas reduction.

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Fact Sheet

Cover Up with Compost

Natural decomposition processes in landfills emit “landfill gas.” Approximately half of that landfill gas is methane, the second leading greenhouse gas emitted in the United States. Landfill methane emissions are of national concern because they are the largest source (approximately 33 percent) of anthropogenic methane emissions in the United States.

Using Compost as a Landfill Cover

In 1998, Austrian scientists Marion Humer and Peter Lechner published the results of research indicating that landfill operators could reduce methane emissions by using compost as a landfill cover. Since then, EPA has worked with Waste Management, Inc. to test the concept in the United States.

Compost provides an excellent environment for the methanotrophic bacteria that oxidize methane. Under test site conditions, compost covers have been found to reduce methane emissions by as much as 100 percent. The covers offer the possibility of controlling these emissions in a cost-effective manner. This is particularly promising for small landfills, where landfill gas collection is not required and where the economics of landfill gas-to-energy projects are
not attractive.

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Composting and Anaerobic Digestion

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Anaerobic digestion

Anaerobic digestion is the process of breaking down organic matter in an oxygen-free environment to generate gas. The gas produced in the process is biogas, a combination of methane and carbon dioxide. The methane can then be burned for energy. The material that remains after digestion (digestate) should then be composted aerobically to complete the process and produce a valuable soil amendment.

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C. Soil Amendments

Soil amendments may be incorporated into agricultural soils used for leafy greens production to add organic and inorganic nutrients to the soil as well as to reduce soil compaction. Soil amendments can contain animal manure or can be composed primarily of plant materials. Soil amendments that contain animal manure are of concern because human pathogens may persist in animal manure (particularly aged manure or inadequately composted soil amendments) for weeks or months (Refs. 10, 11 ) and even longer under certain conditions (Refs. 12-14 ). Proper composting of animal manures via thermal treatment will reduce the risk of potential human pathogen survival. However, the persistence of human pathogens in agricultural soils depends on many factors such as pH, temperature, soil type, and native microflora and continues to be under extensive investigation (Refs. 15-18 ). Leafy greens may be contaminated through contact with contaminated soil amendments if soil amendments containing human pathogens are applied after plant emergence. Field soil contaminated with human pathogens may also provide a means of leafy greens contamination. Therefore, establishing suitably conservative pre-plant intervals, appropriate for specific regional and field conditions, is an effective step towards minimizing risk (Refs. 19, 20 ).

FDA recommends:

• Refraining from use of raw animal manure with any leafy greens crop.


• Refraining from using biosolids as a soil amendment for any leafy greens crop.


• Verifying that any soil amendment that does not contain animal manure has documentation (e.g., ingredient list, statement of identity, or letter of guaranty) from the producer or seller stating that it is manure free.


• Implementing management plans which ensure that the use of soil amendments will not pose a significant potential human pathogens hazard (e.g., timing of applications, storage location, source and quality, and transport).


• Verifying the time and temperature process used during the composting process to ensure that the potential of human pathogens being carried in the composted materials is reduced, controlled, or eliminated as applicable to regulatory requirements.


• Maximizing the time interval between the soil amendment application and time to harvest.


• Implementing practices that reduce, control, or eliminate likely contamination of leafy greens fields that may be in close proximity to on-farm stacking of manure.


• Using soil amendment application techniques that control, reduce, or eliminate the likely contamination of surface water or edible crops being grown in near-by fields.


• Segregating equipment used for soil amendment applications such as compost or using effective means of equipment cleaning and sanitation before subsequent use.


• Minimizing the proximity of wind-dispersed or aerosolized sources of contamination (e.g., water and manure piles) that may potentially contact growing leafy greens or near-by edible crops.


• Obtaining compost from commercial suppliers that maintain temperature monitoring and turning records.


• Obtaining compost from commercial suppliers that have and provide documentation of written standard operating procedures (SOPs), to prevent cross-contamination of finished compost with raw materials through equipment, runoff, or wind.

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2.0 Good Agricultural Practices for Manure Management

Growers should follow good agricultural practices for handling animal manure to reduce the introduction of microbial hazards to produce. Such practices include processes, like composting, that are designed to reduce possible levels of pathogens in manure. Good agricultural practices may also include minimizing direct or indirect manure-to-produce contact, especially close to harvest.

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Probably the first compost formula was the one introduced and developed by Marcus Cato, a Roman scientist, statesman, and general all-round farmer who lived and lectured on agriculture some two hundred years before the Christian era. At least, I think Cato's compost formula is the first that history records. Until the fall of Rome, the teachings of Cato were the last word in farm management. There is little doubt that this old Roman was one of the world's greatest agriculturists. Many of our modern agricultural discoveries were advocated by him.

Cato was a strong believer in compost as the soil builder. Indeed, one gets the idea from his writings that he considered compost making and compost fertilization indispensable if one expected to hold one's land to a high production level. Farm animals were kept as much for what they could supply to the compost pits in the way of manure as for any other purpose.

Cato's method of compost making required two deep, covered pits, one to hold the finished fertilizer, the other to take the stuff as it came from the barnlot or field. On the larger estates the pits were in charge of men who were thoroughly versed in the science of compost making. As a first step in getting the materials ready for the pit, Cato directed that everything should first be scattered in the corrals or used as bedding in the animal stalls, to be trampled under the feet of the livestock. Treating the vegetable materials in this way did two very important things: the trampling broke up the roughage and insured quicker disintegration in the pits; also the spongy material collected the liquid manure which otherwise would go to waste. After this initial treatment, the ingredients went into the pit, where they remained a year. During this period the stuff was turned periodically to bring about uniform disintegration and assure against loss from firefanging.

One of Cato's most interesting -- and certainly progressive -- agricultural principles was that the raw materials must always be composted before being inculcated into the soil. This, he claimed, saved the plant roots from having to do a lot of extra work that was not directly connected with the production of crops. He wanted plant food materials served ready for immediate consumption. No raw manures or other undecayed ingredients should ever be applied directly to the soil.

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