Project: MLMMI 02-HERS-04
To gather and summarise existing knowledge regarding major nutrient inputs (both organic and inorganic fertilizers) and outputs in four agricultural production areas, and then to determine potential "leakage" to the environment.
Funding Partners: who have contributed to MLMMI in support of this project:
MRAC - $26,975
SDIF - $25,000
Manitoba Pork Council and industry groups - $29,025
Amount Funded: $81,000.00
Performer Funded: $0.00
Total Cost: $81,000.00
First Progres report received April 9/02
Second Progress report received Jul 15/02
Final Report due September 14, 2002; Received Oct. 16/02.
A nutrient balance model was developed for the Municipalities of Hanover, La Broquerie, Roland and Sifton in Manitoba. The model tracks and estimates all nutrient (nitrogen and phosphorous) inputs, outputs, and losses to the environment for the agricultural industry. The objectives of this study were to: evaluate the reliability of such a model at both the municipal and farm levels; determine gaps in the knowledge base necessary to implement a nutrient balance model as a planning or regulatory tool; and to provide a preliminary assessment of the nutrient balance in four municipalities that represent a matrix of high and low density crop and livestock production.
Four farms in each of the four municipalities were also used to evaluate the budget model. The purpose of these farm budgets was to further test and evaluate the many estimates of nutrient losses that naturally occur in the nitrogen and phosphorous cycles.
An extensive literature review was conducted to review previous work on nutrient budgets. The nutrient flows in an agricultural ecosystem, including inputs, outputs, transfers and losses from the plant, animal and soil pools were investigated. The literature review focused primarily on the central-northern Great Plains area of North America to ensure that the data would be applicable to soil and climate characteristics of Manitoba.
Considerable data for the municipal model was obtained from the 2001 Census of Agriculture, Manitoba Crop Insurance Corporation records, and a proprietary spatial Grain Flow Model developed by Warkentine and Associates, a local consultant with specialized expertise in the analysis of grain flows in Western Canada. Primary data for the farm-scale budgets was provided by the cooperating farmers. Extensive interviews were also conducted with fertilizer dealers to verify current fertilizer practices by crop producers in Manitoba.
The study found that in areas such as Hanover and La Broquerie, which have a significant intensive livestock industry, the importation of large quantities of nutrients in feed is contributing to a build-up of nutrients in the soil on a regional basis. Manure, however, is not the only source of nutrients that must be considered. The farm case studies confirmed previous studies indicating an excessive buildup of nutrients in soils from the over-application of chemical fertilizers is common.
Notwithstanding the apparent increase in nutrients in these municipalities due to manure, the environmental risks to water resources may not have increased proportionally. The literature review found that the loss of nutrients from fields receiving inorganic fertilizers can be greater than fields receiving manure. Both sources and transport factors have to be considered in assessing transport risk.
Better farm management practices are needed to prevent a build-up of available soil nutrients, regardless of the source of crop nutrients and the size of the farm unit. Regulations to address this issue should be consistent with this principle. Annual soil testing, for example, is practiced by approximately ten percent of producers on approximately one-quarter of their fields in any one year.
The losses of nitrogen and phosphorous to the environment comprise a significant component of the nutrient cycle. Nitrogen losses were equivalent to 35 to 79 percent of outputs, and phosphorous losses were between two and 16 percent of outputs. Some loss of nutrients is a natural part of the nutrient cycle. Further research is necessary to quantify the various losses under “normal” agricultural practices and to understand the impact of these losses on the ecosystem. Critical levels of soil nitrogen and phosphorous for various soils and topographies must be more clearly defined based on environmental risks.
In order to protect the agricultural (livestock and crops) industry and the environment, Manitoba has to conduct research to develop a comprehensive “P Index” that can be used for thresholds and management strategies on a site-specific basis considering both source and transport factors. The RM of La Broquerie would provide an excellent model to conduct site-specific research for better estimating losses of N and P, and strategies for decreasing these losses. More research is needed to better estimate losses as the combination of these losses account for a large percentage of the total outputs. Nitrogen loss research should focus on leaching and denitrification. Phosphorous research should consider losses to surface waters.
Traditional “conservation” farming practices such as grassed waterways, vegetative filter strips, and riparian areas need to be encouraged to a greater extent, as these practices minimize nutrient losses from agricultural lands.
In areas with a high density of intensive livestock operations, there appears to be an excessive use of chemical fertilizers. These nutrient imbalances can be significantly improved, however, with a reduction in fertilizer use.
Nutrient management will need to address more than just fertilizer use to address nutrient imbalances. More precise livestock feed formulations would help decrease inputs for livestock feed. The use of microbial phytase can reduce phosphorous outputs in manure by 30 to 50 percent. In addition, the use of amino acids has been applied in the Netherlands to reduce manure nitrogen content.
On a farm scale, this study revealed that detailed record keeping is required in addition to better estimates of losses to accurately model nutrient flows. Precise estimates of yields, fertilizer use, and manure application rates would increase the understanding of nutrient flow on crop and livestock farms, and provide for strategies to minimize imbalances between inputs and outputs. Regulating only nitrogen encourages N volatilization losses from manure. As these losses increase, manure application rates must also increase to meet crop N requirements. This normally results in an over-application of P, however, which accumulates in the soil. Technologies that reduce N volatilization, such as storage covers and manure injection, can significantly reduce the buildup of P in soils.
Animal manure is utilized on approximately five percent of Manitoba’s agricultural land. The study verified the beneficial impact of manure in increasing soil organic matter which improves soil structure, water infiltration and water storage capacity. Increases in soil organic matter or reductions in the rate of loss of soil organic matter were observed in Hanover and La Broquerie, in comparison to Roland and Sifton. Strategies or programs to encourage the distribution and/or application of manure on a greater land base would benefit most soils in Manitoba.