Poultry Manure as a Fertilizer Source

Table of Contents

Prepared by
J. P. Zublena, Extension Soil Science Specialist; J. C. Barker, Extension Agricultural Engineering Specialist; and T. A. Carter, Extension Poultry Science Specialist

Publication AG-439-5
Revised May 1993 (MOC)

Last Web Update:
December 1997 (DBL)

Poultry manure is an excellent source of nutrients and can be incorporated into most fertilizer programs. Those using manures must practice sound soil fertility management to prevent nutrient imbalances and associated animal health risks, as well as surface-water and groundwater contamination. The key to successful management is to match the nutritional requirements of the crop with nutrients available in the manure. The value of poultry manure varies not only with its nutrient composition and availability, but also with management and handling costs.

Nutrient Composition and Sampling Procedure

The nutrient composition of poultry manure varies with the type of bird, the feed ration, the proportion of litter to droppings, the manure handling system, and the type of litter. Consequently, all manures should be sampled and analyzed for specific nutrient content before you apply them to the land. Waste samples, from North Carolina, can be analyzed for $4 by the North Carolina Department of Agriculture (NCDA), Agronomic Division , Plant Analysis Lab, 4300 Reedy Creek Road, Raleigh, NC 27607-6465. Other qualified private laboratories can also perform the analysis (fees vary).

Collecting a representative manure sample is essential to reliable nutrient analysis. The nutrient value of litter varies greatly within the poultry house. To reduce sample variability, collect subsamples of broiler, turkey, and duck litter in 6 to 12 areas of the house. Samples taken around waterers, feeders, and brooders should be proportionate to the space these areas occupy in the house. At each location, collect litter by digging an area down to the earth; be careful, however, not to include soil. Place the subsamples in a plastic bucket, mix thoroughly, and put 2 to 3 pounds of the mixture in a sample container. Samples from stockpiled litter should be taken from at least 6 locations around the pile, all at depths of at least 18 inches. Subsamples should be mixed and submitted as suggested for litter from poultry houses.

To increase sample uniformity in poultry manure slurries and lagoon sludges, stir them before sampling. Within an anaerobic lagoon, liquids are relatively uniform above the sludge zone; nevertheless, take several subsamples and combine them.

If you cannot have the manure analyzed, use the mean nutrient values for your specific type of poultry manure found in Tables 1 through 4. Table 5 gives the average values for the secondary and micronutrients ordinarily listed in the manure analysis report.

When using mean values for manure nutrient composition, exercise caution to avoid over- or under fertilization. Also, after several years, elements such as copper or zinc may accumulate and reach very high levels. To avoid these problems, take an annual plant tissue and a biennial soil sample to monitor nutrient levels.

Nutrient Availabilities

Except for nitrogen, the availability of most nutrients in poultry manures is fairly consistent. Nitrogen can occur in several forms, each of which can be lost when subjected to different management or environmental conditions.

Nitrogen in poultry wastes comes from uric acid, ammonia salts, and organic (fecal) matter. The predominant form is uric acid, which readily transforms to ammonia (NH₃), a gaseous form of nitrogen that can evaporate if not mixed into the soil. When it is thoroughly mixed, the ammonia changes to ammonium (NH₄⁺), which can be temporarily held on clay particles and organic matter. Thus, soil mixing can reduce nitrogen losses and increase the amount available to plants.

Table 6 lists the first-year nutrient availability coefficients for various poultry manures. Determine the available nutrients by multiplying these values by the nutrient composition values listed on the waste analysis report or in Tables 1, 2, 3, and 4. The NCDA's Agronomic Division calculates available nutrients and lists them in its report.

Application Rate

Land application rates are generally determined by matching the available nitrogen or phosphorus content of the waste to the nutrient requirements of the crop. In most cases, nitrogen requirements determine the application rate, unless the area is designated "nutrient sensitive" and indicates that phosphorus movement off-site can lead to eutrophication of surface waters. In nondesignated areas, phosphorus movement can be adequately controlled with conservation measures such as grass field borders, grassed waterways, contour planting, and reduced tillage, which minimize soil and residual manure movement. Leaching of phosphorus is extremely limited on mineral soils and should not contribute to groundwater contamination.

Nitrogen recommendations for various crops are listed in Table 7. Use these rates as guidelines with realistic yield capabilities for the crop and field. With feed and forage crops, excessive manure application can produce high nitrate concentrations, which can harm livestock (through nitrate poisoning) and promote nutrient imbalances that may lead to grass tetany. If loading rates are to be based on phosphorus, apply the amount suggested by soil-test recommendations. Because the manure may not supply adequate amounts of all the other nutrients required by the crop, be sure to take a soil test and, if necessary, supplement with commercial fertilizer.

In addition to monitoring nutrients, be sure to maintain an adequate soil pH, which will help to maximize crop yields and nutrient availability and promote the decomposition of organic matter. The biological conversion of organic matter to nitrate is an acid-forming process. Take annual or biennial soil samples to monitor pH changes. When livestock wastes are applied at agronomic rates, high salinity (excess salt) has not been a problem, given normal amounts of rainfall in North Carolina.

A worksheet to help you determine land application rates is included at the end of the text.

Timing and Uniformity of Manure Applications

To minimize nitrogen losses, apply manure as near as possible to planting time or to the crop growth stage during which nitrogen is most needed. Surface water and groundwater contaminations are greater in areas of high rainfall and when manures for spring crops are applied in fall or winter. For coarse-textured soils, manures should be applied frequently and at low rates throughout the growing season because such soils have a high water infiltration rate and a low ability to hold nutrients. Unused nitrogen can therefore be lost by leaching.

Exercise caution when applying lagoon liquid by irrigation on crops undergoing stress (for example, corn during an extended drought). A heavy coating of manure solids on the leafy vegetation can cause ammonia burn. Except in extreme cases, this damage is usually short term and does not significantly reduce yields. With concentrated lagoon liquids, use several small applications rather than one large dose.

Whether poultry waste is applied by manure spreaders or irrigation systems, you must apply it uniformly. A lack of uniformity leads to nutrient excesses and deficiencies, lower yields, and variable crop moisture at harvest time.

Acreage Requirements for New Facilities

Whenever manure or lagoon liquid samples are available for analysis, they should be used to determine application rates and acreage requirements. When you are planning new facilities, however, the average values can help determine approximate acreage requirements for a poultry operation of a given size. Table 8 gives minimum acreage requirements for various nitrogen fertilization rates. This table can be used to estimate the minimum acreage required to use all of the manure.

Suppose that a producer is interested in building two broiler houses with a combined 50,000 bird capacity/growout. The producer is planning to spread this litter on a bermudagrass hay field capable of producing 6 dry tons per acre. From Table 7, the bermudagrass will require 300 lb nitrogen per acre (6 tons x 50 lb N/dry ton). How many acres of bermudagrass would be needed for the entire year's waste? Using Table 8, under surface broadcast column 300, we find that each 1,000-bird capacity would require 0.65 acre for land application of broiler litter. For a 50,000-bird growout operation (0.65 x 50), the producer would need 32.5 acres for a year's worth of litter.

Value of Manure

When comparing manure to commercial fertilizers, convert total manure nutrients to available nutrients by using the availability coefficients. Consider the following example. Analysis of the available nitrogen, phosphorus (P₂O₅), and potassium (K₂O) content in a broiler litter sample that will be incorporated shows that it contains 43 pounds of nitrogen per ton, 62 pounds of phosphate per ton, and 37 pounds of potash per ton. If the current fertilizer prices for nitrogen, phosphate, and potash were as follows: $0.23 per pound of nitrogen; $0.22 per pound of phosphate; and $0.12 per pound of potash as potassium chloride. One ton of broiler litter would be worth the following:

(43 x $0.23) + (62 x $0.22) + (37 x $0.12) = $27.97 per ton

This value would not cover hauling, handling, or application costs, nor would it include the value of other essential nutrients available in the manure. In addition, it assumes that the soil test has recommended each nutrient, when, in fact, many may not be needed. Nutrients not needed should not be considered when you assess the manure's value.

Land Application Worksheet

Farmer Jones is preparing to spread broiler litter on a field and incorporate it within two days to supply nutrients to his corn crop. Last year, he grew soybeans in the field.

His corn-yield goal is 140 bushels per acre, and he has decided to apply the equivalent of 140 pounds of nitrogen per acre (Table 7). His land is not subject to erosion, is not in a nutrient-sensitive watershed, and has grassed borders and waterways to further reduce the potential of runoff.

Farmer Jones used a starter fertilizer on his corn crop at a rate to supply 10 pounds of nitrogen per acre and 34 pounds of phosphorus per acre. He intends to supply the rest of his nitrogen needs by applying broiler litter with a litter spreader and incorporating it within two days.

How much litter does he need to spread in order to meet the nitrogen needs of his corn crop? Will he need to supplement the crop with additional potash or phosphate to satisfy his soil-test recommendations of 50 pounds per acre of each nutrient? The answers are given in the following worksheet. Use Table 9 to estimate available nitrogen carry-over from legumes.

The authors wish to acknowledge the assistance and cooperation of the North Carolina Department of Agriculture's Agronomic Division in the analysis of samples and the development of the data used in this publication.