The scoop on compost
By Peter Darbishire
Creating compost is not rocket science, but using it requires a scientific approach to maximize its benefits.
There was a time when spreading ‘well rotted manure’ on land was seen as an easy way to reduce the pile behind the barn and, certainly, help out the crop. Then science enabled growers to balance crop nutrition with commercial fertilizer and the pile behind the barn was left to rot. Now, given our concern for the environment and a recognition that some of the old ways had their place in crop production, research is demonstrating how compost can be an important component of best management practices.
“At first it didn’t seem the economics were right to create and use compost,” comments Dr. Katherine Buckley of Agriculture and Agri-Food Canada (AAFC) in Brandon, Manitoba. Then the cost of commercial fertilizer began to increase and the environment became an issue, and agriculture came under scrutiny by some groups. As always, growers themselves wanted to be more active in preserving the environment and compost became more interesting.
|Composting can provide a portion of a crop’s nutrient requirements. Photo By Peter Darbishire.|
“Our experiments are in the eighth year and we are starting to see the possibilities for using compost effectively,” Dr. Buckley continues. “Compost works well with all crops except flax, is easier to transport to the field because volume is reduced by about 75 percent, and it does not have the odour and insect problem that comes with manure.” When a starter nitrogen application is used in conjunction with compost, according to Dr. Buckley, it can be an extremely effective crop production tool. There are microbial benefits with compost and it can restore degraded soils.
“We’ve done work on soil reclamation in the oil and gas industry and, of the combinations we examined, compost worked the best,” says Dr. Frank Larney, a researcher with AAFC in Lethbridge, Alberta. “We looked at using compost as a replacement for top soil that was removed from well sites beginning in 1997.” After four years of growing crop on the reclaimed soil the project was turned back to the land’s owner for production. In 2007, Larney and his colleagues re-examined the soils to see if the reclamation had been sustained. He expects results on these tests to be available in 2008. Using this example, he suggests that compost has some very real benefits when used on ‘at risk’ areas of fields, such as knolls and sections where erosion is a problem.
Larney and Buckley see compost as an important additive to any cropping system, particularly on marginal land, property with erosion problems and for crops that require more organic matter. However, the challenges facing growers who want to begin using compost as part of their regular crop production practices are the creation of the compost and short-term yield reductions that can occur when moving to a strategic combination of compost and commercial fertility products.
Creating compost can be simple or complex depending on the time and effort willingly expended on the operation. In the old days, manure was left to rot with no intervention on the part of the farmer. While this method will result in compost, the end product may not be desirable as weed seeds may still exist in the mix. Larney says that in order to create a uniform product that is free of weed seeds and pathogens, the mix needs to reach a temperature of 55 degrees C or better for up to two weeks. The temperature is achieved by adding oxygen to the manure by aerating it or turning it and mixing it. “Achieving the right temperature is important to create a sanitized product,” he explains.
Again, the process can be simple or demanding. A front-end loader can be used to mix the pile depending on its size; in very small operations this may be the most economical. PTO driven windrow turners that mount on a tractor can effectively turn 400 tonnes of material per hour are also available. For very large operations, such as feedlots, a self-propelled turner may be the most effective equipment to use. In the end, there is an economic balance between the time and energy required to turn the manure to create compost and the savings in reduced reliance on commercial fertilizers and the yield that can result from an improved soil profile.
“The costs of creating and using compost, rather than raw manure, can be offset by reduced transportation costs due to the large reduction in volume of material that occurs during the composting process,” Buckley explains. “The most costly part of getting into compost is developing a proper site to accomplish the task by ensuring an impermeable surface under the pile and a means to manage run-off.” Certainly, there may be some capital costs, she adds, but that will be amortized over time.
In terms of yield reductions that can occur when compost is used as a fertilizer replacement, Buckley suggests this is a short-term issue which can be managed by balancing the nutrition in the compost with commercial products. “I prefer to consider compost as a phosphorus product and not the main nitrogen source,” she says. In fact, she recommends that nitrogen be applied in conjunction with compost. “Combined with commercial fertilizer, compost nutrition can be optimized if the mixture is right.”
In an eight year crop production study conducted at the AAFC Research Station in Brandon, beef manure compost with and without starter nitrogen were compared to commercial fertilizer in the first four years of a durum wheat, flax and barley rotation. In the last four years of the study, annual and perennial forages and winter wheat were grown without any additional nutrients to determine the capacity of a compost addition to sustain crop production and develop a measure of the true value of compost. The results were not earth-shattering, but savings on commercial fertilizers were substantial.
“We did get improved yield without the use of commercial fertilizer,” Buckley explains. “The cost benefit is there, but it takes a number of years before it shows. However, the result
of using compost on poor soils is incredible and definitely worth considering.” A complete economic analysis of this particular research is being tabulated, but there is documented research that shows an economic benefit of using compost in potato production and during a one year in three application of compost in wheat or barley. So far, the Manitoba research has focussed on cereals and forage, but the next step will be an analysis of compost use with canola.
|Compost is an important additive, particularly on marginal land. Photo By Bruce Barker.|
Growers wanting to work compost into their cropping operations should follow some simple guidelines for success. Larney suggests testing for the presence and amount of nutrients in the compost, test the soil for nutrients, compare the results with the requirements of the crop being planned and then try to balance the compost’s available nutrition with the addition of commercial nutrients. “If your soil tests high with nitrogen or phosphorus, it may not be wise to put compost on that field,” he says.
“The best place for compost is land that is eroded or in need of improved organic matter.” He adds that field mapping will indicate areas in a field that would benefit from compost application. Larney views compost as a soil amendment to improve soil quality and not as a complete source of nutrition. “Compost improves the properties of soil to allow the soil to hold water and enable better access to nutrition,” he says.
Grandpa may have had the right idea about transporting the pile from behind the barn to the field, but modern technology and science have made the process much more effective. In a world obsessing about carbon foot printing and the need to produce more food, using compost may help in both those areas while maintaining a grower’s competitive edge. Considering the long-term, proven benefits of compost application on fields and the environmental sustainability that can result, the effort to make compost may be worthwhile. -end-
A compost primer
Compost is the result of manure decomposition. In nature, this will happen naturally, but farmers can speed the process by doing the following:
1. Prepare a site for composting to minimize any environmental problems. A preferred location would have an impermeable base, either hard clay soils or a cement pad. As well, some consideration for minimizing effects of run-off should be made, such as a sloped drainage ditch.
2. Pile the manure in windrows or small piles on the base.
3. Turn or mix the piles periodically to encourage decomposition.
4. Ensure a temperature of the compost of 55 degrees C for at least two weeks.
5. When compost has a dry, crumbly texture, has a low carbon-to-nitrogen ratio (13:1 to 10:1), low oxygen demand, low temperature and earthy odour, it is ready to spread on the soil.
Depending on the size of the pile or windrow, the number of times it is turned and the air temperature and amount of moisture, compost could be ready in about three months. For
more comprehensive instructions on how to make compost, the On-Farm Composting Handbook by Robert Rynk, published by Northeast Regional Agricultural Engineering Service, Ithaca, New York, is considered the ‘Bible’ of composting instruction.
For access to scanned portions of the handbook go to compost.css.cornell.edu/
OnFarmHandbook/onfarm_TOC.html. To order a copy, go to www.nraes.org and look under ‘Large-scale composting’ or call 607-255-7654. -end-
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