When, where, and how to treat your landbase with organic manure
By Loretta Sorensen
If the cost pencils out, applying manure to pastures is likely to increase forage yields.
But analyzing costs is just the first step in preparing to apply manure to a pasture. Other key activities in a successful application include:
- Soil testing
- Manure analysis
- Determining application rates
- Controlling the rate applied
- Documenting when and where manure is applied
Iowa State University Assistant Professor in Ag & Biosystems Engineering, Daniel Andersen, encourages landowners to “be sure you understand how and where to apply this ancient fertilizer.”
“Your state’s Department of Natural Resources, Department of Environmental Quality or County Extension Services are helpful in identifying application regulations for your location,” Andersen says. “Across the nation there’s great emphasis on water quality, and it’s extremely important to thoroughly understand and comply with water quality regulations.”
While there are some manure application regulations that apply nationwide, laws vary from state-to-state and can vary within different counties.
Producers using nutrient management plans are required to complete soil testing on distribution sites every few years. While sampling soil to see what nutrients it contains isn’t absolutely required for a small distribution, it can be helpful in determining the effectiveness of manure application.
“Soil sampling can be valuable if you’re targeting specific areas of a pasture and want to verify that you’re not over applying nutrients,” Andersen says. “If you’re not soil sampling before applying nutrients every few years, it’s probably not a big risk, unless you’re regularly applying manure to a site over 15 to 20 years.”
Diet, housing, manure storage types, environmental conditions, management techniques and treatment practices all affect nutrient content. Manure sampling is helpful in determining nutrient cost if it’s being purchased and to assist in defining application rates. (See Andersen’s “How to Sample Manure for Nutrient Analysis” at store.extension.iastate.edu/Product/How-to-Sample-Manure-for-Nutrient-Analysis.)
Andersen’s research has revealed that some nutrient quality is naturally lost during storage, and the type of storage also affects nutrient quality. His studies have also documented that manure accumulation and the storage process affects nutrient content. Daily scrape and haul facilities retain between 65% and 80% of nitrogen; manure pack facilities retain between 60% and 80% of nitrogen; open lots retain between 45% and 60% of nitrogen. Under floor pits retain between 70% and 85% of nitrogen and anaerobic lagoons retain between 15% and 30% of nitrogen.
Haul times, as well as being costly, also affect nutrient value, all of which means that testing content is necessary to determine nutrient cost and application rates. Testing helps identify high levels of nutrients like phosphorus, which typically occurs in cattle manure. Andersen advises carefully fertilizing pastures and fields, and using legume mixtures to help balance the fertility manure provides.
Technological advances make it much easier to haul manure, but if a haul is too long, it reduces the value as well as increasing application expenses. Andersen’s research has shown that haul length can be further than often believed and remain economically viable.
Tested haul lengths include: Swine slurry, 5 to 20 miles; dairy slurry, 2 to 13 miles; beef solids, 9 to 20 miles; layered manure, 16 to 34 miles and turkey litter, 13 to 19 miles.
When to apply?
The timing of nutrient application is important for numerous reasons. Avoiding runoff is critical in order to comply with nutrient application regulations and to avoid losing the benefits of the manure.
“Early spring or fall are typical application times for row crops,” Andersen says. “For a small grain like oats or wheat, there may be a summer application window after harvest. The window of time for applying manure to a pasture is much larger than for row crops, but application should be made during the growing season. The one time everyone should avoid is ice-covered or snow-covered soil, which leads to significant runoff and loss of nutrient quality.”
For irrigated pastures, since most available soil nitrogen is either taken up by plants or lost through environmental processes, fertilizing can be beneficial. Soil sampling would be very beneficial to accurately assess any other nutrient deficiencies. Avoiding over irrigating and late spring grazing will contribute to the benefits of manure application on irrigated pastures.
In contrast to commercial fertilizer, manure, when properly distributed, has potential to increase soil carbon and reduces atmospheric carbon levels. It also reduces soil erosion, runoff and nitrate leaching. Use of manure also lowers energy demands for natural gas-intensive nitrogen fertilizers.
In addition to the nitrogen, phosphorus, potassium and micronutrients manure adds to the soil, it also adds carbon.
“Organic carbon from manure is used as an energy source for the active, healthy soil microbial environment,” Andersen says. “That stabilizes nutrient sources and makes the nutrients available to crops.”
Manure organic matter contributes to improved soil structure, which means improved water infiltration and greater water-holding capacity. Those elements lead to reduced stress during dry periods, reduced soil erosion and reduced nutrient leaching.
Manure applied to the soil surface acts like crop residue to significantly reduce raindrop impact, which can detach soil particles, leading to soil erosion. Organic nitrogen has also been shown to be more stable than nitrogen applied in the form of commercial fertilizer. A significant portion of organic manure is slowly released as soils warm and plants seek nitrogen. Commercial nitrogen is mobile and soluble in water.
“When manure is applied, it must come in contact with the soil so nutrients are captured,” Andersen says. “Be sensitive to significant rainfall after application, as that could lead to leaching. To successfully apply manure, it helps to have detailed knowledge about each pasture where it’s distributed.“
The cost of manure will vary from source to source since nutrient values span a wide range. However, a range of $25 to $60 per 1,000 gallons of liquid or 2,000 pounds (1 ton) of solid manure is representative of the current market.
“You see quite a few small farms partnering with livestock producers or manure sources to contract for applying manure to fields and pastures,” Andersen says. “It’s an opportunity for both parties to utilize this available resource and save some money at the same time.”
Because grazing animals leave behind much of the nutrients they consume, it’s estimated that cow manure returns between 75% and 95% of the phosphorus and potassium. It takes between 40 and 50 pounds of nitrogen to grow 1 ton of cool-season grasses and about 75% of that is lost when the grass is grazed.
To avoid a flush of extra forage growth in spring, plan to apply manure in late summer. Forage response is less but forage quantity is greater for warm season grasses than it would be if nutrients weren’t applied.
Since pasturelands don’t easily leach nutrients over winter, a fall application typically loses less than 5% of the nutrients by spring. Pastures with a significant percentage of legumes may not need the nitrogen since they biologically fix nitrogen for their own use and provide some to grasses.
Application could be split into two or three applications throughout the growing season to stimulate pasture production from early to mid-June through early to mid-August.
Over-feeding an area can have a negative impact on subsequent forage, so it’s important to work with a specialist to pinpoint appropriate application rates.
“Most universities have an Extension specialist who can assist in determining general application rates,” Andersen advises. “They can also provide information about a preparing a written contract that outlines responsibilities of the buyer and seller, who agrees to pay for what and who’s liable in the event of a spill.
“Make sure the application consistently hits the specified rate,” Andersen adds. “With today’s equipment, manure is routinely hauled from the source farm to where it’s needed.
Composting – large scale(Source – Imperial Compost, Brawley, CA
Manure from the feedyard is trucked to the composting facility where it is dumped in rows.
Water is then added to the rows by truck or sprinklers. Moisture content must be raised to and maintained at 40% for optimum microbial activity. Through the respiration process, the microbes give off heat and CO2. The temperature rises to 131 degrees Fahrenheit to begin the composting process.
At this point, each composting row is mechanically mixed every three days for 8 turns. This turning reduces the particle size to increase the rate of break down, and aerates and mixes the windrow to manage the temperature and oxygen levels.
Oxygen levels must be maintained at a minimum of 5% to support aerobic microbial activity. When there is adequate oxygen present, the process does not produce objectionable odors.
To complete the composting process, the compost windrow is sprayed with water to create an exterior crust to seal in the interior moisture so that the final phases of organic decay may be completed.
Imperial Compost’s uniform, consistently high quality compost requires from 60-120 days from process start to finish.
Advantages of Composting
- After three days of composting
at 131° F, Escherichia coli, Salmonella and Listeria
monocytogenes are no longer present.
- Reduction in fly larvae.
- Stops weed seed germination