Monday, December 11, 2023

Maximizing poultry manure use through nutrient management planning

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By Drs. Casey W. Ritz

& William C. Merka

Special to Poultry Times

ATHENS, Ga. — Poultry manure fertilizer contains all the essential nutrients required for crop production, and its value as an organic fertilizer and a source of plant nutrients has been recognized for centuries. Even with its beneficial effects on plant growth, however, manure constitutes only a small percentage of the nutrients applied to cropland when compared to commercial fertilizer.

Poultry manure fertilizer is not used to its maximum potential for several reasons, including:

(a) Lack of information on its value as a source of plant nutrients,

(b) Failure to recognize how and where to use it, and

(c) Lack of recognition of its economic value.

This article provides current information about the appropriate application and most effective use of poultry fertilizer. It will also help poultry producers develop a simple nutrient management plan that meets permitting authority standards.

Quantity of fertilizer

Georgia’s poultry industry produces large quantities of poultry manure. Georgia’s yearly poultry production is estimated at 1.3 billion broilers, 12 million commercial laying hens, 11.8 million broiler breeder hens and 12 million replacement pullets. The manure these birds produce is a valuable by-product with a potential gross value of more than $60 million.

For each pound of feed consumed, a chicken will produce approximately 0.5 pound of fresh manure with a moisture content of about 75 percent. The manure rapidly loses water due to evaporation, and the final product typically has a moisture content of 20-40 percent, depending on bedding type and quantity, bird concentration, watering equipment and ventilation systems.

Manure production can vary substantially with management programs, so on-farm records are the most accurate means of determining manure production for each operation. Manure production estimates are as follows: 2.5 pounds per broiler, 20-30 pounds per commercial layer, 44 pounds per broiler breeder, and 8 pounds per replacement pullet.

Fertilizer composition

Poultry litter from floor-raised birds (broilers, turkeys, broiler breeder pullets) consists primarily of droppings and bedding (usually wood shavings or sawdust). Feathers and waste feed make up the remaining litter components. Poultry manure consisting of only fecal droppings is associated with caged layers and broiler breeders. Liquid manure from some laying hen operations is typically stored in lagoons — biological digesters in which bacteria decompose organic matter into gases, liquids and sludge.

Poultry litter and manure vary in both physical and chemical composition. Factors affecting composition include: type of birds raised, number of birds per unit area, feed nutrient density, bedding material type and amount, time in use and other management factors. Environmental factors during production and storage and post-production handling methods also influence poultry manure composition.

It is often necessary to stockpile poultry litter when producers clean out their facilities. The litter should be placed in a structure that will prevent surface or groundwater contamination. Generally, stockpiled litter will go through some degree of composting. As a result, the level of certain plant nutrients, especially nitrogen, will change. Broiler litter nutrient quality has been improved by housing multiple flocks prior to cleaning out the poultry house. It is now customary to produce four to six flocks per year followed by an annual clean-out.

Based on average nutrients, a ton of poultry litter has an estimated value of $41. A 20,000-bird broiler house will produce approximately 150 tons of litter per year (6 flocks) with a potential gross value of $6,150. A flock of 14,000 breeder hens will produce approximately 150 tons of manure (50 percent dry weight basis) per year with a potential gross value of $4,300.

The cost of transporting poultry litter varies. Litter removed from a broiler house is usually very bulky (67 cubic feet per ton), increasing its transportation cost per pound of nutrient. The average delivered cost for commercial operators is $20 per ton of broiler litter; thus, litter can provide an economic benefit for many growers if it is effectively marketed.

Fertilizer application

To maximize poultry litter’s nutrient value, incorporate it into the soil immediately after spreading. Forty to 70 percent of the total nitrogen is available during the first six weeks. The remaining nitrogen will be slowly released as organic residues decompose and may require more than one growing season. For optimum utilization, use poultry fertilizer to meet as much of the crops’ phosphorus and nitrogen needs as possible, then use commercial fertilizer to furnish other nutrients to the levels needed as indicated by a soil test.

Phosphorus in chicken manure is predominantly in organic form and becomes available much more slowly than nitrogen, being directly related to the rate at which the manure decomposes and its binding qualities within the soil.

Potassium is present in chicken manure as both an inorganic salt in the excretions from the kidneys and in the living and dead cellular material in the feces. All forms of potassium in manure are readily available in most cases but may be rapidly lost by leaching if not incorporated.

Many other elements are present in chicken manure in small quantities. Little is known about the rate of release of these elements, but essentially all become available through decomposition. These elements are not thought to significantly affect either plant fertility or environmental factors.

In addition to being an excellent source of plant nutrients, poultry fertilizer can increase the soil’s water infiltration rates by improving its structure. On a short-term basis, poultry fertilizer can also increase the soil organic matter content.

Poultry fertilizer can be successfully used on many crops. A successful utilization program includes the following:

(1) Obtaining a soil test for application fields.

(2) Calculating crop nutrient requirements.

(3) Obtaining manure nutrient analysis.

(4) Ensuring proper application rates.

To prevent excessively applying poultry fertilizer and potentially contaminating surface and ground water, prepare a nutrient budget worksheet for each field or crop. Contact your county Extension agent for assistance generating site-specific field budgets.

As indicated previously, the actual nutrient profile of a particular manure sample may vary. Having your manure analyzed for its true plant nutrient content is recommended. Armed with this and appropriate soil test information, you and your county agent can decide on the best plan of action to use poultry fertilizer for your individual cropping needs.

Record keeping

Keeping accurate records of all your poultry and commercial fertilizer uses and off-site transfers is an essential component of a working nutrient management plan. On-farm field applications and off-site manure transfers should be recorded. Such records can help to validate your use of appropriate BMPs (best management practices) and environmental stewardship practices on the farm should the environmental impact of your farm ever be called into question.

Drs. Casey W. Ritz and William C. Merka are Extension poultry scientists associated with the University of Georgia in Athens, Ga.

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