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Because the cost of commercial fertilizers is rising, farmers are looking for alternative sources of nutrients for their crops. At the Milan No-Till Field Day University of Tennessee soil scientists Forbes Walker and Neal Eash will explore this topic in depth.

The most commonly available alternative fertilizer sources for many farmers are animal manures and poultry litters from livestock operations, biosolids (treated sewage sludge) from municipal waste water treatment operations and legume winter cover crops.

The scientists say the nutrient content of animal manures varies depending on the species and age of the animals, their diet and how the manure is handled and stored. "During the normal handling and storage of many dairy and swine manures, water is added making it difficult to estimate nutrient content without conducting a laboratory analysis. In most cases it is not economical to transport liquid manures more than a few miles from where they are produced," said Eash.

On the other hand, Walker points out that poultry litter is a relatively dry material consisting of the mixture of bedding materials and manure from the broiler operations. "A typical broiler litter will have a nitrogen (N), phosphorus (P) and potassium (K) content similar to a 2-2-2 or 3-3-3 NPK fertilizer, or around 30 pounds of plant-available nitrogen and 40 to 60 pounds of phosphorus (as P2O5) and potassium (as K2O) per ton. At current prices this represents a nutrient value of approximately $30 to $40 per ton," Walker said. Storing the litter will increase phosphorus and potassium concentrations.

Both scientists remind producers that biosolids are often available at no cost from local water treatment plants. Biosolids have to meet federal standards for pathogens and heavy metal concentrations before they can be used as fertilizer sources. Class A biosolids can be land-applied with few restrictions, whereas Class B biosolids have some use limitations. Quick lime is commonly used in the processing of many biosolids. Lime stabilized biosolids can be used as an alternative lime source, a source of organic matter, phosphorus and to a lesser extent nitrogen.

Another alternative is planting winter legume cover crops such as hairy vetch (Vicia villosa Roth) or crimson clover (Trifolium incarnatum L.). These have been demonstrated to reduce crop nitrogen needs for a following crop by up to 60 pounds of nitrogen fertilizer per acre. The costs associated with cover crops include the cost of the legume seed. An additional benefit with cover crops is the protection of soil and reduction in erosion over the winter months.

"It is important to base the application rates of alternative fertilizer materials on nutrient analyses and crop requirements determined from soil test recommendations," Eash cautioned. "Application methods should be selected that do not negatively impact the environment or the crop quality. The application of biosolids to meet crop nitrogen needs will over-apply phosphorus and may negatively impact the environment. The application of manures and poultry litter to meet crop nitrogen needs will over-apply both phosphorus and potassium, and may negatively impact forage quality through the luxury uptake of potassium."

More details on this topic will be available from the scientists on Tour G throughout the field day.

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Contact: Patty McDaniels, (865) 974-7141