STEP 4   Methods and Timing for Manure Application

The method used for manure application depends on the volume and consistency of the manure, the hauling distance, fuel costs, capital costs, and existing equipment (Minnesota Department of Agriculture 1995a). Poor manure management practices include spreading manure on frozen or compacted soils, manure application in excess of crop requirements, and improper storage facilities (Davis et. al. 1997). The potential for contamination from manure is affected by characteristics of the manure, and the method and rate of application. Liquid manure applied at rates greater than the soil infiltration rate or water-holding capacity can promote runoff. Injection or incorporation of applied manure reduces runoff.

Table 1.   Predicted losses of ammonium N between spreading and incorporation of manure under various weather conditions (losses expressed as percentage of total ammonium N spread) (Adapted from Janzen 1998 and Danesh et al. 1999).

Methods of Application

Broadcasting
Broadcasting is the primary application method for solid, slurry and liquid manure (Minnesota Department of Agriculture 1995a). Application techniques include box spreaders, tank wagons, tow hoses, and irrigation systems. Broadcasting requires the least amount of energy and time, and results in a uniform application pattern. However, surface broadcasting promotes loss of N to the atmosphere, and the organic fraction decays slowly on the soil surface.

Banding
Banding is the placement of fertilizer in a concentrated layer or location (band) in the soil, commonly 8-15 cm (3-6") below the surface. Fertilizer bands can be placed with the seed, below the seed, or both. Research carried out in the Lower Fraser Valley of B.C. is consistent with European studies that showed that banding manure is more effective than broadcasting on perennial ryegrass and winter wheat, particularly in the summer (Bittman et. al. 1999a). Surface banding requires half the power of injection units to pull around the field. Also, there is no root pruning with banding, unlike injectors. Placing manure on the soil surface where it is exposed to sun and air may reduce pathogens (Bittman et. al. 1999a). To overcome the difficulties of injection into grassland, a system was developed for applying manure in bands on the soil surface underneath the grass canopy. This sub-canopy band application system chops slurry then delivers it via individual hoses to shoes that drag along the ground surface beneath the grass canopy (Bittman et. al. 1999a).

A number of studies are under way to enhance the ability of producers to apply manure to grassland (Zebarth and Paul 1997). The sub-canopy band applicator is an attachment to a liquid manure tank, which applies 5 cm (2") - wide bands of slurry to the soil surface beneath the forage grass canopy. The B.C. Dairy Producers’ Conservation Group has obtained a farm-scale sub-canopy hand applicator. Custom application has provided excellent results and has met farmer expectations (Zebarth and Paul 1997).

Injection
Injection methods are beneficial as they place liquid manure below the soil surface, eliminating both surface runoff on sloping soils, and volatilization of ammonia from the manure on any soil. However, injection can significantly increase loss of N by denitrification and leaching to groundwater.

Injection equipment can be added to liquid and slurry spreaders (Minnesota Department of Agriculture 1995a). Current injection systems do not fit well into direct seeding systems or zero-tillage operations, because they cause extensive soil disturbance (PAMI 1997a). PAMI (1997a, 1997c) has developed a high-volume slurry injection system that mounts to a standard cultivator. Sweeps provide complete coverage of manure, reducing odour. Incorporation relies on nozzles close to the ground, either ahead or directly behind a tillage tool. Crop striping also appeared to be less of a problem when compared to machines with wider row spaces. The injection system offers the following advantages:

• Maximizes the fertilizer value of liquid swine manure;
• Reduces odour during the application process;
• Reduces the potential of nitrate pollution due to over-application;
• Provides well-distributed nutrients for efficient crop use;
• Handles slurry trash such as straw, hair, and other foreign materials;
• Can operate in fields with very heavy surface residues and long stubble.

PAMI has evaluated openers for low disturbance injection of hog manure into zero till as well as pasture or forage (Hultgreen and Stock 1999). One of the openers tested, the Yetter Avenger Coulter, is built specifically for manure injection, and was among the best of the systems tested in terms of soil disturbance, leaving sufficient stubble standing for good snow trapping (PAMI 1999).

The Aerway manure applicator was developed at the Agriculture and Agri-Food Canada in Agassiz, B.C. in cooperation with Holland Hitch of Surrey, B.C. for spreading liquid manure (Alberta Agriculture, Food and Rural Development 1999b). Rotating knives make a small furrow in the ground where the manure is released at ground level. With the knives spaced 15 cm (6") apart, the manure is applied more evenly and with less soil disturbance than injection equipment and with a reduction in odour. The Aerway can be used on cultivated land, pasture or zero-till cropland, and currently is being tested in Alberta.

Pipeline manure injection systems (sometimes called hose-drag systems) describe systems that inject manure into the soil using a tractor-powered implement connected by a long flexible hose to a pump and an irrigation pipeline. Pipeline manure injection systems can reduce nutrient loss and control odour, but they are costly (PAMI 1997a). The significant costs involved might be justified if a group of producers jointly purchased a system. An operation with approximately 250 dairy cows or 13,000 to 14,000 finished pigs per year is at the break-even level in terms of affording a hose drag system (Wehrspann 1998). Custom applicators will charge on average .006 to .0117 cents (US) to pump manure up to a mile (Wehrspann 1998).

Table 2.  Advantages and Disadvantages of Various Application Methods (Dutton and DeLuca 1996).

Special Considerations for Various Types of Manure

Table 3 summarizes manure management operations and the associated equipment or process required for solids, slurries and liquids.

Table 3.  Components of manure handling system for various types of manure (Manitoba Agriculture 1994)

Solid Manure
Solid manure (containing more than 16% solids) and semi-solid manure (containing 11-16% solids) can be transported to the field in an open spreader or dump truck. Slurry waste (about 4-10% solids) requires handling with special pumping equipment, such as tank wagons or pump and pipeline systems.

Care should be taken to apply manure at the correct rate, and uniformly across the field. Operate the application equipment so that spray drift does not enter a watercourse or leave the property. Reduce soil compaction by not driving repeatedly over the same areas of the field with heavy loads of manure (Minnesota Dept. of Agriculture 1995a). The use of rapid-transport trucks with wide or flotation-type tires results in less soil compaction under a variety of soil conditions (Sutton 1994). Another application alternative is the large self-propelled semi-truck tanker units used to haul large volumes of manure to distant fields, where the liquid manure is loaded into smaller machines for field application.

Liquid manure
Liquid manure should not be applied at rates that bring the soil to field moisture capacity, because this promotes surface runoff or leaching (Johnson and Eckert 1995). Slurry should be injected into the soil immediately, to reduce the risk of nutrient loss, odour problems, and water pollution. (Minnesota Dept. of Agriculture 1995a).

The B.C. Ministry of Agriculture, Fisheries and Food (1993) recommend that equipment used for the spreading of dairy manure should:

• be of tight construction so manure will not spill from it during transport,
• be operated in such a manner that the wheels do not carry manure onto public roadways, and
• be filled in such a manner that manure does not spill from the sides of the equipment creating unsanitary, messy conditions.

They also stipulate that manure irrigation equipment should have all connections securely fastened to avoid leaks that could cause contamination.

The rapid expansion of the hog industry has encouraged the development of improved systems for managing liquid manure. Improvements included improved rate and uniformity of application; development of ramps close to the ground with drag hoses, multiple splash plates close to the ground; duck-foot, knife, or disk incorporators; and low pressure or gravity applicators (Barnett 1997).

Special consideration must be given to soil characteristics if you choose to pump your manure (Minnesota Dept. of Agriculture 1995a and 1995b). Runoff or ponding of manure may occur from poorly drained soils. On sloping terrain, manure application rates should be less than the soil infiltration rate to prevent runoff.

As manure is pumped from a holding area, the nitrogen level in the manure remaining in the holding area decreases and the phosphorus level increases. The TR 6000 manure injection truck monitors the available N, P and K at the time of pumping and application. Additional chemical fertilizer can be added to the flow to meet predetermined requirements of nutrients on a per hectare or acre basis for each field, and this can be controlled by GPS. The manure is injected with sweeps deep enough so that odour is not an issue. According to the Western Producer (1999), use of the TR 6000 to apply liquid hog manure imparts a savings of about $42/ha ($17/ac) over the cost of using chemical fertilizer, whereas the savings when conventional equipment are used are only $17/ha ($7/ac). Broadcasting imparts a saving of $40/ha ($16/ac), but odour and nutrient losses are important issues.