Theresia K. Lavergne

Animal waste is not necessarily waste at all and can be a valuable resource in agriculture. The nutrients nitrogen, phosphorus and potassium in animal waste can be recycled into other facets of agricultural production.

The articles in this issue of Louisiana Agriculture illustrate how LSU AgCenter scientists provide research-based information that helps livestock, dairy and crop producers utilize nutrients produced on their farms in environmentally-conscious ways. Much of the animal waste research conducted by LSU AgCenter scientists focuses on the poultry and dairy industries. The poultry and dairy industries produce their commodities in confinement and collect their wastes in various ways. Thus, managing the nutrients (waste) produced by these animals is an important aspect of produc   tion, and the articles within this issue address the means of treating the waste for re-use, alternative methods of handling animal waste to ensure its safety when re-used, and the methods of re-using animal waste.

The poultry industry is the largest animal agriculture industry in Louisiana, and broiler production is the major component of this industry. Almost 1 billion pounds of broiler meat are produced in Louisiana each year. Commercial broilers are produced in 11 parishes including Bienville, Claiborne, Jackson, Lincoln, Natchitoches, Ouachita, Sabine, Union, Vernon, Webster and Winn. The gross farm value of poultry production is approximately $600 million each year, with the total value (including value-added) exceeding $1 billion. Broilers are produced in total confinement housing, and there are approximately 2,000 broiler houses in Louisiana. These broilers produce more than 178,000 tons of litter (manure and bedding material) each year. The litter is used as fertilizer for pasture and hayfields.

The dairy industry also is an important animal agriculture industry in Louisiana. Approximately 273 million pounds of milk are produced by more than 20,000 cows in 14 parishes. Three parishes in southeast Louisiana and one parish in northwest Louisiana produce more than 93 percent of the total milk in the state. The gross farm value of milk amounts to about $39 million each year, with the total value of the industry exceeding $110 million. Primarily, Louisiana’s dairy industry is a pasture-based system, but a small percentage of the industry is in total confinement systems. These mature dairy cows produce more than 311,000 tons of waste (feces and urine) a year, and more than 102,000 tons of this waste is captured in confinement systems and during holding periods. This waste is utilized as a fertilizer for pastures and other crops.

With a combined total of 280,000 tons of poultry and dairy waste produced in Louisiana each year, producers must handle animal waste in an environmentally-friendly manner. If not handled properly, water runoff from land that animal waste has been improperly applied to or stored on can reduce surface and groundwater quality by introducing excessive levels of nutrients such as nitrogen and phosphorus, organic matter and pathogens into the environment. The excessive runoff of these nutrients into our waterways can result in degradation and contamination, which could make waterways unsafe for swimming and fishing. Even more severe, high levels of nutrients (nitrogen and phosphorus) can lead to excessive algal growth in waterways that can cause hypoxia and fish kills.

Articles in this issue provide data on the effectiveness of best management practices (BMPs), which are implemented to minimize the effect of production agriculture on water quality. Also, these researchers provide information on reducing soil phosphorus when animal wastes are applied to land over time.

Poultry diets can be formulated to result in less excretion of total phosphorus by the broilers fed those diets. The inclusion of the enzyme phytase in broiler diets allows nutritionists to reduce the amount of total phosphorus in broiler diets without negatively affecting growth performance, while reducing the total amount of phosphorus excreted by the broilers. Thus, the total phosphorus in their litter is reduced.

The level of phosphorus in diets for dairy cows also is a concern related to phosphorus excretion. Thus, researchers are evaluating the effects of reducing the phosphorus in lactating dairy cow diets, and they have reduced phosphorus excretion by as much as 30 percent.

Best management practices help keep waterways from becoming impaired. LSU AgCenter researchers recommend that producers implement a 20-foot buffer (unfertilized zone) – for land with a zero to 5 percent slope – along waterways when they are applying poultry litter as a fertilizer to maintain good water quality. In addition, restricting the access of cattle or other animals from waterways will help protect water quality.
 
Much of the waste produced by poultry and dairy is utilized as fertilizer for pasture or hayfields. Research in the LSU AgCenter has focused on litter application rates and uptake of phosphorus by several different grasses. In general, the trends indicate that yields of grasses increase with an increased level of litter application. Phosphorus removal from the soil by the harvested grass increases, too.

Poultry litter is a valuable fertilizer for cotton production. Researchers have reported that cotton yields increased as the application of poultry litter increased from zero to 4 tons per acre.

Alternative methods of treating animal waste are being developed by LSU AgCenter scientists, and these methods may generate revenue for producers. Researchers are separating dairy manure from bedding sand with a self-cleaning screen, which allows the bedding sand to be reused. Also, this separator reduces the waste going into lagoons. Furthermore, these researchers have been working to develop a solar still to dry wet dairy manure, as well as poultry litter. By drying the manure and litter, bacterial contamination can be reduced, and the dry material is a safer fertilizer.

Another LSU AgCenter animal waste project is a lime-precipitation system that removes phosphorus from dairy parlor wastewater and destroys pathogens. The result is water that is practically odor-free and clear, while the phosphorus is separated and can be removed from the farm. Also, a Dairy Waste Treatment Evaluation System, built by the LSU AgCenter, can remove pollutants from wastewater by physical, chemical and biological means. Both systems produce a product low in nutrients or pathogens, which reduces the possibility for dairy waste to contaminate waterways.

The economics of dairy lagoon cleanout and the economics of moving animal wastes off a farm and transporting them to other locations where the waste can be utilized also are included herein. The availability of a federally funded cost-share program for dairy lagoon cleanouts provides a financial benefit in the form of nutrients for producers’ fields and crops. And, the models for economic feasibility of transporting dairy manure and poultry litter indicate that the value of the nitrogen, phosphorus and potassium can still be realized when transported as far as nine miles for dairy manure utilized on hay fields, and as many as 22 miles for poultry litter utilized for crops such as corn, cotton, sorghum or wheat.

The Louisiana Cooperative Extension Service serves an important role in the AgCenter’s animal waste efforts. Extension agents take the research-based information to agricultural producers through farm visits and at field days, as well as through bulletins and extension publications. The Louisiana Cooperative Extension service is the link between the research scientists and the agricultural producers who can implement the developments and discoveries from the LSU AgCenter.
 
Much of the research within this issue was funded through a Tillage, Silviculture and Waste Management grant provided by the U.S. Department of Agriculture. This federal assistance is critical to conducting this research, and Louisiana’s congressional delegation was instrumental in helping obtain this money for our agricultural producers.

Through research-based information developed by LSU AgCenter scientists, agricultural producers can improve their environmental stewardship, reduce the impact of agricultural production on the environment, and utilize the valuable nutrients in animal waste.

Theresia K. Lavergne, Associate Professor, School of Animal Sciences, LSU AgCenter, Baton Rouge,

(This article was published in the spring 2010 issue of Louisiana Agriculture.)