(Beyond Pesticides, July 1, 2010) A recent study by Seong Park, Ph.D., published in the Agronomy Journal, demonstrates that manure generates higher economic returns than anhydrous ammonia, a synthetic fertilizer. Dr. Park, a research economist with Texas AgriLife Extension Service found no significant difference in yield between organic and chemical nutrient sources.
The long-term experiment conducted in the Oklahoma Panhandle compares the use of pig and beef manure to anhydrous ammonia in irrigated corn fields. The region has seen rapid growth of animal population and density. The use of animal manure for fertilizer not only reduces or eliminates the need for synthetic fertilizers, it also significantly reduces waste management costs.
Dr. Park found anhydrous ammonia to be the most costly source of nitrogen, due to purchase price, which is not normally required when using beef or swine manure. Swine effluent had the lowest application costs since it can be applied through existing irrigation equipment. The only additional cost would be equipment to pump effluent from the lagoon where it is stored to the center pivot. Beef manure and anhydrous ammonia require application machinery. Beef manure is however a more economical choice if it is being transported to crops on another farm. Swine effluent is too bulky to be transported to other producers.
In addition to lower costs the use of organic fertilizer may result in healthier soil. Manures contain important micronutrients. Dr. Park found that throughout his experiment plots treated with manure had higher soil pH than plots treated with anhydrous ammonia. Continued application of anhydrous ammonia can actually lead to acidification causing reduced yield.
A 2009 study comparing manure from conventional and organic dairy cows shows manure from organic diary operations may replenish soil nutrients and potentially protect nearby water sources by reducing the runoff of agricultural pollutants. Cows on organic dairy farms generally consume feeds fertilized with manure instead of synthetic fertilizers. Researchers believe organic management may improve the rate at which nutrients in the manure are converted into forms readily taken up by crops. Researchers found the manure from organic farms had more types of phosphorus that are slower to dissolve. Slow release fertilizers are more likely to be taken up by crops and less likely to be washed out of fields becoming a source of nutrient pollution in nearby water bodies.
A related study conducted by the Agricultural Research Service (ARS) shows chicken litter, an organic fertilizer composed of chicken manure and bedding material, has advantages over chemical fertilizer. Previous studies only considered the amount on nitrogen, potassium, and phosphorus when determining the economic value of chicken litter, but a recent study conducted by ARS agronomist Haile Tewolde and colleagues looks at the value of chicken litter as a soil conditioner. A soil conditioner is a material added to soil to correct deficiencies and improve plant growth and health. The researchers found peak cotton yields to be 12% higher with organic fertilizer than peak yields with synthetic fertilizer.
For small organic gardens, composting can be a safe alternative to harsh chemical fertilizers.
Organic agriculture relies on natural sources of fertilizer such as manure, instead of potentially dangerous chemical sources. When used as a fertilizer, manure is turned from a hazardous waste product into a resource. Beyond Pesticides supports organic agriculture as effecting good land stewardship and a reduction in hazardous chemical exposures for workers on the farm. The pesticide reform movement, citing pesticide problems associated with chemical agriculture, from groundwater contamination and runoff to drift, views organic as the solution to a serious public health and environmental threat.