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Research Identifies Environmentally Sustainable Management Practices to Improve Pasture Productivity

by 5m Editor
30 July 2007, at 8:21am

CANADA - A research project underway southeast of Winnipeg is shedding new light on the value of swine manure fertilizer when applied to pasture and hayland.

The multi-disciplinary project is a collaborative effort involving university researchers, industry and the federal and provincial governments which is exploring best management strategies to improve the productivity and environmental sustainability of grassland pasture systems.

The work is being coordinated by the University of Manitoba’s National Centre for Livestock and the Environment on a quarter section of land located just southeast of La Broquerie, Manitoba. A team of researchers is evaluating the effect of swine manure fertilizer on hay and pasture yields and quality, the impact on the productivity of the cattle that consume the forage, and several environmental sustainability considerations including nutrient loading and movement, pathogen movement and greenhouse gases.

Swine Manure Offers Readily Available Source of Plant Nutrients

“Many of our pastures and our haylands in Manitoba are what we would classify as native or unimproved pasture which are relatively nutrient deficient,” explains Dr. Kim Ominski, an associate professor with the U of M’s Department of Animal Science.

She notes the expansion of the hog sector in Manitoba has created a potential source of nutrients in the form of liquid hog manure. She explains that the benefits of adding nutrients are well known and now researchers are looking at the benefits of those nutrients when provided in the form of hog manure. The question that is now being asked is: “Is the production system sustainable?”

One aspect of the study compares the effect of three different treatments: no manure applied, manure applied in the spring and in the fall and manure applied in the spring only. The forage produced is removed as harvested hay or through grazing cattle.

Forage Yields and Livestock Productivity Increases

Dr. Ominski observes, “From a productivity perspective we’re seeing significant increases in both forage and animal productivity.”

She estimates forage yields at the site have increased between two and a half to three fold allowing a substantial increase in the number of grazing days per hectare.

She also indicates that they are seeing significant increases in the number of kilograms of live weight of animal removed from the system – easily a three to three and a half fold increase in live weight gain.

Nutrient Loading and Movement and Greenhouse Gas Emissions Monitored

A second aspect of the study examines the level of manure nutrients, primarily nitrogen and phosphorus, remaining in the soil or going into the ground water and at the emission of greenhouse gases, including nitrous oxide and methane, into the atmosphere from soil and from dung and urine.

Dr. Mario Tenuta, a soil ecologist with the Department of Soil Science and Canada Research Chair in applied soil ecology, explains researchers are doing extensive surface soil sampling for available plant nutrients and periodic deep sampling taking care to prevent the contamination of different soil layers sampled. As well, in conjunction with PFRA (Prairie Farm Rehabilitation Administration) and Manitoba Water Stewardship, water on the site is being monitored through a series of groundwater wells to detail incremental changes in water chemistry.

Nutrients Show Minimal Movement

Dr. Tenuta observes, “What we’re seeing is that there is an accumulation of nutrients in the very near soil surface, particularly the zero to five centimeter depth. The nutrients are really staying and sticking there. We’re finding a buildup of roots which are associated with an increase in above ground biomass as well. At depth we’re not finding nitrogen or phosphorus beyond 30 centimeters depth and we’re not finding it in the ground water at all. As for greenhouse gasses we’re finding that there’s a lot lower greenhouse gases if the manure is applied in the fall than if the manure is solely applied in the spring time.”

Dr. Don Flaten, a professor with the Department of Soil Science adds, “There’s no evidence of nitrate contamination going down into the profile or into the ground water. There’s no evidence that the phosphate is moving down into the ground water, at least at this stage.”

However he notes one nutrient that is sometimes present in hog manure that has been detected moving down is chlorine. Chlorine is not used in large quantities by a crop and it’s not degraded by microorganisms, it’s not incorporated into soil organic matter. However, chlorine is relatively inert in soil and it’s not an issue in terms of health or the environment.

Dr. Tenuta points out the manure that is being applied to this site is very high in prosperous, higher than what most producers would be using.

“It has a high solid content so what we’re trying to do is accelerate the accumulations and see what time frame it does happen and if it does happen at all. This is a very coarse textured soil so it’s the right spot to be in. We haven’t seen anything yet moving.”

Microbial Contamination and Bacterial Resistance Tracked

As well scientists are monitoring microbial contamination of groundwater and the potential for the development of antimicrobial resistance.

Dr. Denis Krause, a professor with the Departments of Animal Science and Medical Microbiology notes researchers have tracked E. coli, as well as microbial communities rich in particular kinds of antibiotic resistance from groundwater that potentially could be contributed by antibiotics used in the hog industry.

He observes, “In terms of the E. coli we find that E. coli from hog manure do not survive on pastures for very long periods of time at all. We also find that E. coli that are spread from hog manure that have been spread on pasture typically do not find their way into cattle that are grazing the pasture. We also find that there isn’t a great deal of background antibiotic resistance in microorganisms in the groundwater.”

He stresses, “They do not come from any digestive tract source. That means that there’s a huge amount of background antibiotic resistance in the environment and that’s something that we’ve seen in the literature from other research groups that is in fact quite common.”

He suggests that there are a lot of other issues going on and that there are a lot of other sources of microbial contamination in potable water sources other than the livestock industry.

“The nitrogen is not accumulating at all. The phosphorous is accumulating and we’re monitoring how many years that will be until it may be of a concern.”

Unfair to Link Hog Production to Antimicrobial Resistance

Dr. Krause insists it would be extremely difficult to point the finger solely at the hog industry as a major contributor to antibiotic resistance, either in the environment or in human medicine, because there’s already so much background antibiotic resistance, the result of antibiotic producing organisms that are typically found in soil.

Cooperative Spirit Recognized as Critical

Dr. Flaten stresses, “The collaboration and partnership effort out here is just tremendous. This project is the result of an incredible array of partnerships. Not just partnerships among scientists but between scientists and extension staff and between our private industry partners and their scientists and producer groups.”

Research Results in Environmentally Sustainable Productivity Improvements

Dr. Ominski believes the production results need to be coupled with the environmental sustainability results because, while farmers are looking to optimize productivity, they want to do so in a fashion that’s environmentally sustainable.

She notes support at this site from the commodity groups and from provincial and federal governments has been tremendous. “We view this as an opportunity for us to, in an unbiased way, look at the potential to increase productivity but ensure we're always doing it in a fashion that is environmentally sustainable.”

5m Editor