Land Application of Livestock and Poultry ManureMonday, March 12, 2012
Factors affecting the fertiliser value of manure and recommendations for application are covered by Mark Risse, Extension Engineer at the University of Georgia's Department of Biological and Agricultural Engineering, as well as practical aspects on how much manure can be applied and handling solids in liquid manure.
Livestock and poultry manures contain nutrient elements that can support crop production and enhance the chemical and physical properties of soil. Manure can be an asset to livestock and poultry operations when its nutrients are used for fertiliser.
This publication provides information on (1) the nutrient content of manures available for land application, (2) how to determine manure application rates and whether supplemental fertiliser will be needed for maximum crop production and (3) how to use management techniques to maximise the fertilization potential of farm manures.
Factors Affecting Fertiliser Value of Manure and Recommendations for Application
The type and amount of nutrients in livestock and poultry manures and the nutrients’ eventual availability to plants may vary considerably. Some factors affecting nutrient value of applied manure are type of ration fed, method of collection and storage, amount of feed, bedding and/or water added, time and method of application, soil characteristics, the crop to which the manure is applied, and climate.
Increasing levels of various elements (copper, arsenic, etc.) and inorganic salts (sodium, calcium, potassium, magnesium, etc.) in feed will increase their concentrations in manure. There is concern about the potential toxic effects to plants of high concentrations of heavy metals and salts in soil as a result of high application rates of manure to the land. Perform regular soil tests and manure analyses to monitor the balance of nutrients in the soil on your farm, especially on land receiving heavy manure applications. From an environmental standpoint, limit the rate of manure application to the needs of the crop grown on the land.
Bedding and water dilute the nutrient concentration of manure and reduce its value. On the other hand, feed spilled and incorporated into the manure increases the nutrient concentration. Excessive feed spillage and/or inadequate agitation may cause sludge build–up in liquid systems, making removal of the manure more difficult.
The type of housing and/or waste handling system you use greatly affects the nitrogen (N) concentration of manures (Table 1). Major nitrogen losses occur when manure is dried by sun and air movement or leached by rain, as is the case in open lot systems. In contrast, manure loses comparatively little nitrogen in a completely covered facility using a manure pack or liquid pit storage system. Loss of nitrogen is greatest in long-term treatment or storage systems such as oxidation ditches or lagoons.
|Table 1. Approximate nitrogen losses from manure as affected by handling and storing methods|
|Handling, Storing Methods||Nitrogen Loss*|
|* Based on composition of manure applied to the land vs. composition of freshly excreted manure.|
Phosphorus (P) and potassium (K) losses are minimal (five to 15 per cent) for all but open lot and lagoon manure handling systems. In an open lot, you can lose from 40 to 50 per cent of the manure‘s phosphorus and potassium to run–off and leaching. However, most of the phosphorus and potassium can be retained for fertiliser use by run–off control systems (setting basins, detention ponds). In lagoon systems, from 50 to 80 per cent of the phosphorus in manure can settle in the sludge layer and thus be unavailable if only the liquid portion is applied to the land.
It is possible to realise maximum nutrient benefit from manure if you incorporate it into the soil immediately after land application (Table 2). Incorporation minimises nitrogen loss into the air and/or in run–off and also allows soil microorganisms to start decomposing the organic matter in the manure, thus making nutrients available to the plant sooner. In addition, incorporation of manures into the soil minimises odour.
|Table 2. Approximate nitrogen losses from manure to the air as affected by application method|
|Application||Type of Nitrogen Manure||Method Loss|
|Broadcast without cultivation||Solid
|Broadcast with cultivation1||Solid
|* per cent of total nitrogen in manure applied which was lost within 4 days after application.
1 Cultivation immediately after application
Generally, phosphorus and potassium losses are negligible and are not affected by the method of application; however, incorporating manure minimises phosphorus and potassium losses due to surface run–off. Apply manure as uniformly as possible to prevent local concentrations of ammonium–nitrogen or other inorganic salts that can reduce seed germination and crop yields.
By applying manure just before the planting date of crops, you maximise plant nutrient availability, especially in high rainfall areas and on porous soils having rapid percolation. However, do not plant immediately after heavy manure application. Salt accumulation near the soil surface and/or a temporary excess of ammonia resulting from the break–down of organic nitrogen lower germination and reduce seedling growth. As an alternative, late fall applications may be desirable because of labour availability, field conditions, etc. Even though fall applications may result in five to 10 per cent total nitrogen loss, the extra time allows soil microorganisms to more fully decompose the manure and release its nutrients for use during the following cropping season. This is especially advantageous for solid manure that contains much organic matter.
For sandy or coarse-textured soils, manures can best be applied frequently and at low rates throughout the growing season to provide environmental protection and maximum plant growth. Soils with more than 10 per cent slope should not have manure applied or if applied, use injection of liquid manure into sod.
Not all manure nutrients are readily available to a crop in the year of application. To be used by plants, nutrients in manure must be released from the organic matter in a water-soluble form. Manure nitrogen is in ammonium (inorganic) and organic forms. Potentially, plants could use all of the ammonium–nitrogen in the year of application. Nitrogen in the organic form, however, must be ‘released’ before plants can use it. In other words, the organic nitrogen must be converted to ammonium (NH4)+ or nitrate (NO3)- before it can be used by plants. Approximately 75 per cent of the total nitrogen will be available to crops during the year of application with the remainder carried over and available the next cropping season.
However, the rate of availability of nitrogen is largely influenced by soil, climate, etc. In contrast, nearly all the phosphorus and potassium in manures are available for plant use during the year of application.
Table 3 shows the pounds of nutrients excreted annually by various livestock per 1,000 pounds liveweight. The nutrient content of manure from your farm might differ considerably from the values presented here. These figures can, however, serve as a guideline for planning purposes. Nutrient analysis of the manure is highly desirable.
|Table 3. Annual pounds of nutrients in manure as excreted per 1,000 pounds liveweight|
|Dairy Cow||Beef Feeder||Swine Feeder||Laying Hen||Broiler|
|Elemental P and K conversion can be made as follows: to convert P2O5 to elemental P, multiply by 0.44; and to convert K2O to elemental K, multiply by 0.83.|
Determine How Much Manure Can Be Applied
You can only determine the exact amount of nutrients available for land application from your operation by laboratory analysis. But you can use Tables 1, 2 and 3 to calculate the approximate nutrient value of your manure from Table 3, then subtract storage and handling losses (Table 1) and application losses (Table 2) to get the nutrients available at time of application. With these figures you can estimate the amount of manure to apply to a given crop area and whether your crop will require additional commercial fertiliser.
If you know the quantity of nutrients available from your operation per year, you can determine how much land is needed for manure disposal. Table 4 gives nutrient needs for various crops. Apply to the land at such a rate that the amount of available nutrients does not greatly exceed the amount removed by the growing crop.
|Table 4. Approximate N, P2O5 and K2O utilization by various crops|
|Crop||Yield/Acre||Nutrient Uptake, lb/A*|
|Corn (grain)||150 bu
|Bermudagrass (Hybrid)||6 tons
|Sorghum/Sudan Hybrid||8 tons||360||122||466|
|Grain Sorghum||6,000 lb||225||63||180|
|* Figures given are total amounts taken up by the crop in both the harvested and the above-ground unharvested portions. These numbers are estimates for indicated yield levels taken from research studies, and should only be used as general guidelines.|
A swine producer has a 1,000–head finishing operation (averaging 125 pounds weight per animal) in an enclosed confinement building. Liquid manure is collected in a lagoon. If the manure is spread by irrigation annually on land producing 150 bushels of corn per acre, how many acres are required for maximum fertiliser utilisation?
Determine the nutrient needs of the crop. From Table 4, for 150 bushels of corn: N = 225 pounds/acre, P2O5 = 80 pounds/acre, K2O = 215 pounds/acre.
Determine the nutrient value of manure from Table 3. Pounds nutrient/year/animal unit in manure as excreted: N = 164, P2O5 = 124, K2O = 132. Reduce nitrogen value 80 per cent for storage losses (Table 1) and 30 per cent for application loss (Table 2). This means only 23 pounds of N/1,000 pound animal unit are available for crop utilisation. At 125 pounds/head, the number of 1,000–pound animal units = 1,000 head × 125 lbs/head divided by 1,000 lbs/animal unit = 125 animal units.
To determine total pounds of each nutrient available, multiply unit values by number of animal units:
P2O5 = 62 × 125 = 7,750 pounds*
K2O = 66 × 125 = 8,250 pounds*
* Assumes 50 per cent recovery with little or no agitation of the lagoon.
Determine number of acres required for maximum nutrient utilisation. Divide total pounds of each nutrient (from Step 2) by pounds of that nutrient required per acre (from Step 1).
Acres Required for P2O5 = 7,750 ÷ 80 = 96.8
Acres Required for K2O = 8,250 ÷ 215 = 38.4
Thus P2O5 is the acreage-determining nutrient if nutrients are fully used. Manure should be applied over 96.8 acres to assure maximum utilisation of the manure (in actual practice, phosphorus and potassium are often over–applied to allow more nitrogen application). Make up the remaining nitrogen and K2O required for production with commercial fertiliser.
Determine supplemental fertiliser needed (total needs - supplied). Since manure will be applied over 96.8 acres, the following total amounts of N, P2O5, and K2O will be required:
P2O5 = 96.8 × 80 (from Table 4) = 7,744 pounds
K2O = 96.8 × 215 (from Table 4) = 20,812 pounds
Supplemental nutrient requirements may be determined by subtracting nutrients available in manure (from Step 2) from total nutrients required as follows:
Supplemental P2O5 required = 7,744 – 7,744 = 0
Supplemental K2O required = 20,812 – 8,250 = 12,562
Solids in Liquid Manure
Flushing gutters with recycled water from lagoons can be a major obstacle when solids content is higher than pumping equipment can handle. A major handicap can occur when dairy free–stall bedding, for example, gets in the flush gutters and ultimately into lagoons. Table 5 shows typical solids content of some liquid waste handling systems.
|Table 5. Typical solids content of some liquid waste handling systems|
|VS/TS* (%)||Solid Content (%)|
|Feedlot Run–off||Less than 1|
|Dairy Barn Wash Water||Less than 1|
|Single or First Stage Swine||1/2-1|
|Cattle (no bedding)||1-2|
|Second Stage||Less than 1/2|
|Volatile Solids/Total Solids. Volatile solids will dissipate and volatilize into the air over time. Values do not include any bedding.|
The chart in Figure 1 shows the relationship of the liquid manure solids content to viscosity or consistency and type pump required.
Some additional management techniques that will help ensure safe and effective application of manure to crop–land follow:
- Incorporate manure into the soil immediately. Otherwise, apply manure to surface at reasonable distances from streams, ponds, open ditches, neighbouring residences and public buildings to minimise run–off and odour problems.
- Minimise odour problems by using common sense, especially during the summer. Spread early in the day when the air is warming up and rising rather than later when the air is cool and settling, and do not spread on days when the wind is blowing toward populated areas or when the air is still. Good management helps avoid neighbour complaints. Analysis from liquid manure varies considerably depending on the amount of dilution. Laboratory analysis is recommended for all animal waste and soil samples are recommended as well. Table 6 shows average nutrients in liquid manure.
- Apply manure to relatively level land — if slope exceeds 10 per cent, knife liquid manure into sod.
- Agitate or mix liquid manure thoroughly in pits to facilitate removal of settled solids and thus ensure uniform application of the nutrients.
- Consider irrigating with dilute manures (lagoon or run–off liquids) during dry weather to apply needed water and nutrients to growing crops.
- Wash the plants with clean water to avoid leaf burn when irrigating manure on growing crop.
- Avoid spreading liquid manure on water-saturated or frozen soils where run–off is apt to occur.
- Apply sufficient water sometime during the year to avoid accumulation of salts in the root zone of soils in arid regions.
- Use good safety measures when moving manure from tanks or pits. Because of oxygen deficiency or toxic gas accumulation, avoid entering storage structures when agitating the liquid manure.
The chemical and physical properties of soil, such as water infiltration rate, water–holding capacity, texture and total exchange (nutrient–holding) capacity also affect how much manure can be safely applied to land. Fine–textured soils have low water infiltration rates; therefore, the rate at which liquid manure, especially lagoon effluent, can be applied without run–off may be restricted to the intake rate of the soil.
Coarse–textured soils, on the other hand, are quite permeable and can accept higher rates of liquid manure applications without run–off. But because most coarse soils have a very low exchange (nutrient–holding) capacity, you may have to apply smaller amounts of manure during the growing season to minimise the chance of soluble nutrients entering ground water. Organic matter in the manure is decomposed more rapidly in coarse–textured than fine–textured soil and during warm, moist conditions rather than cold, dry conditions. However, fine-textured soils will retain the nutrients longer in the upper profile, where plants can get them.
|Table 6. Nutrients in liquid manure: approximate fertiliser value of manure – liquid handling systems|
|Animal||Waste Handling||Dry Matter||Available N||Total N||P2O5||K2O|
|%||lbs/1,000 gal of waste|
|Dairy cattle||Liquid pit
|* Lagoon – Including lot run–off water
Note: There will be little odour if manure is immediately incorporated.