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Manure happens – Make the most of it

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Manure happens – Make the most of it

Nutrient and soluble salts overloading can lead to environmental problems but only when manure is mismanaged.

July 2, 2008, Lethbridge, Alb. – Ground and surface water quality degradation from agricultural sources is seen by some as an increasing environmental problem. While excessive applications of manure can eventually result in nutrient, soluble salts and trace elements overloading, and can lead to environmental problems, this results only where manure is mismanaged.

“When proper manure management practices are followed, animal wastes can be utilized as a valuable nutrient resource rather than treated as a waste,” says Dr. Ross McKenzie, research scientist – agronomy, Alberta Agriculture and Rural Development, Lethbridge, Alb. “Manure is an excellent organic fertilizer containing nitrogen (N), phosphorus (P), potassium (K) and many other essential nutrients. Manure can physically benefit the soil as it adds organic matter to the soil, which improves soil tilth and structure. There is no question that adding modest amounts of manure to soil is very beneficial; however, too much of a good thing over a period of time could lead to problems.”

Intensive livestock operators must use best manure management practices (BMP) tailored to match the needs of each farm. BMP will vary from farm to farm depending on the climatic zone of the farm, the type and number of animals in confinement, the total amount of manure produced and how the manure is handled, stored and applied. BMP also depend on the amount of land available to apply manure, soil types on the farm, types of crops grown and crop yield potential. Producers must take a pro-active approach to manure management to ensure the sustainability of both their farm and the environment. Following a step-by-step approach is essential in planning best manure management practices for each farm.

“The place to start is to determine how much manure is produced by the livestock operation,” says McKenzie. “The most accurate way to calculate the amount of manure an operation produces is to weigh every truckload of manure that leaves the operation. Alternately, use an average truck weight and then count the number of truckloads of manure removed.”

Having a suitable on-farm location to store manure is the next factor to consider. For solid manure, storage capacity for up to six months is needed to accommodate the wait for appropriate application times. The storage site must be on soil with very low permeability to prevent contaminants from seeping into the subsoil and eventually the ground water. It is very important to ensure leachate from the manure piles cannot leave the storage area in surface runoff during periods of heavy rain or rapid snowmelt. In the case of liquid manure storage, seepage from the containment area must be prevented, which could entail lining containment areas with flexible membranes or other approved types of impermeable material. In all cases, surface water runoff must be diverted away from manure storage areas to prevent contamination of surface water.

“The factors of ‘where to apply the manure’ and ‘what rates to apply’ require the greatest attention,” says McKenzie. “These two factors go hand-in-hand and involve identifying the fields where manure can be applied, determining the acreage of each field and soil testing each field.”

Soil sample information is needed to identify which nutrients are deficient in each field to determine how much of each nutrient must be added to the soil to ensure adequate levels for crop growth.

Ideally, soil sampling to a depth of four feet (1.2 metres) is recommended every few years to ensure that a nutrient leaching problem is not developing. If a leaching problem is recognized, it can be dealt with before it becomes a serious concern.

“Representative manure samples should be taken each year and analyzed for total and available nutrients, specifically nitrogen, phosphorus and potassium,” says McKenzie. “When determining manure application rates, available nutrients and the portion of the unavailable nutrients that will be released from manure in the year of application must be matched to crop nutrient requirements in each field.

“It is virtually impossible to apply manure to meet exact crop requirements for all nutrients. When manure is applied based on one nutrient, other nutrients either will be over or under applied. For example, if feedlot manure is applied to meet the nitrogen requirements of wheat or barley, phosphorus will be applied at approximately three to six times the rate of crop removal. Repeated applications over a period of years will result in build up of high soil phosphorus levels.”

Most producers have applied manure based on nitrogen content, leading to a build up of soil phosphorus. Producers in this situation will have to take serious steps to draw down soil P levels and avoid manure or P fertilizer application for a period of years. To draw down the P levels, it may be necessary to only apply manure to meet P crop requirements and supplement with nitrogen fertilizer.

“When developing a long-term manure management plan, producers have to decide whether to apply manure based on N or P,” says McKenzie. “In the long-term, it is advisable to use phosphorus as the nutrient to match with crop removal rather than nitrogen.”

All the information that producers gather has to be put together to develop manure management plans. Alberta Agriculture and Rural Development has developed a new booklet – Nutrient Management Planning Guide (2007) – to assist producers with this exercise. Although it seems a daunting, it is essential in planning a manure use program and optimizing crop production.

Remember – manure happens, so make the most of it!