Alberta Soil Phosphorus Limits Project

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 Introduction | Conclusions | Recommendations | Index to final report volumes | Research publications | Acknowledgements


The application of soil amendments, such as inorganic fertilizers, manure, biosolids, and wastewater, can improve soil fertility. However, many of these amendments, particularly organic materials such as animal manure, are often applied in excess of crop nutrient requirements. A build-up of nutrients in soil can be a significant risk to surface and ground water quality.

Phosphorus is an important nutrient for optimum crop production, but the movement of phosphorus from agricultural land to surface water can cause water quality degradation through accelerated eutrophication. Livestock production has been identified as a primary source of agricultural phosphorus in surface waters. Water quality studies in Alberta showed that as agriculture intensity increased in watersheds, the amount of phosphorus increased in streams.

The Agricultural Operation Practices Act was revised to protect soil and water quality through regulation of Alberta's confined feeding operations. The regulations under this Act include manure application limits based on nitrogen, but do not include soil phosphorus limits. It is well known that manure applied based on nitrogen will result in the accumulation of phosphorus in soil, which poses a risk to surface water quality. These concerns about phosphorus led to the establishment of the Alberta Soil Phosphorus Limits Project in 1999. The objectives of the project were:

  1. To develop recommendations for phosphorus limits for agricultural land in Alberta;
  2. To determine implications of soil phosphorus limits to the agricultural industry;
  3. To identify management options for soil phosphorus limit implementation; and
  4. To develop recommendations for an action plan and a time line for implementation of limits.
The Soil Phosphorus Limits Project was implemented in two phases. Phase 1 of the project (1999 to 2002) included the collection and review of background material related to agricultural phosphorus issues, a simulated rainfall study in the laboratory, and field studies in central Alberta. The following Phase 1 studies helped define the direction of the Soil Phosphorus Limits Project.
  • Phosphorus loading effects on water quality in Alberta.
  • Assessment of how other jurisdictions in North America and Europe have approached agricultural phosphorus issues.
  • Assessment of agronomic phosphorus thresholds for Alberta crops.
  • Assessment of phosphorus water quality limits in streams.
  • Phosphorus sources and sinks in watersheds.
  • Laboratory study to assess the relationship between soil-test phosphorus levels and phosphorus in runoff from representative Alberta soils.
  • Assessment of soil-test phosphorus levels relative to phosphorus levels in the stream for an agricultural watershed.
Phase 2 (2002 to 2006) involved a series of research studies, hydrology studies, and computer modelling studies designed to:
  • Collect and assess soil and water quality data under Alberta field conditions in order to better understand the relationship between soil phosphorus and phosphorus in runoff from agricultural land;
  • Define the relative risk of runoff for Alberta's agricultural areas for use in calculating site-specific soil phosphorus limits; and
  • Determine soil-test phosphorus limits that will maintain phosphorus concentrations in runoff water below set limits.
The Phase 2 studies included the following actions.
  • Assess the relationship between soil and runoff phosphorus in eight representative microwatersheds in Alberta's agricultural area.
  • Assess the relationship between soil and runoff phosphorus in simulated rainfall runoff from manured land for representative Alberta soils.
  • Relate phosphorus sorption to phosphorus runoff characteristics, and determine saturation thresholds for Alberta soils.
  • Compare different core sampling techniques to a frame-excavation method to determine soil-test phosphorus concentrations for Alberta soils.
  • Assess the economic impacts of legislated soil-test phosphorus limits on confined feeding operations in Alberta.
  • Determine potential runoff volumes from Alberta landscapes using provincial soil and landform information, long-term climatic and hydrometric data, and hydrological modelling.
  • Determine soil-test phosphorus limits for all agricultural land in Alberta.

The following general conclusions were developed from the background information and research findings generated through the Alberta Soil Phosphorus Limits Project.

Phosphorus as a nutrient
    1. Phosphorus is an essential nutrient in agricultural systems and is important in nutrient management to achieve optimum crop production. Soil-test phosphorus (i.e., plant-available phosphorus) levels do not need to exceed 60 ppm (about 120 kg/ha) in the top 15 cm of soil to achieve optimum growth for most crops grown in Alberta. Crops grown on soils with phosphorus levels in excess of 60 ppm generally do not respond to phosphorus additions.
    2. Most soils in Alberta are deficient in soil-test phosphorus. Analysis of soil test records from the agricultural areas has shown that most soils have soil-test phosphorus levels that are significantly below 60 ppm, which is considered the agronomic threshold level for most crops. Crops grown on these soils will benefit from addition of phosphorus. In general, soil phosphorus levels in the 1990s were similar to phosphorus levels in the 1960s for most agricultural areas in Alberta.
    3. Even though soil-test phosphorus levels are generally low, phosphorus losses from agricultural land are recognized as a significant contributor to surface water quality degradation. Livestock production systems, including cow-calf operations and confined feeding operations, are considered the primary source of agricultural phosphorus losses. For cow-calf operations, over-wintering of cattle near surface water bodies can be a significant source of agricultural nutrient loss. Manure spreading related to confined feeding operations is also a significant source of excess phosphorus in surface water.
Phosphorus in runoff
    4. Excess phosphorus in agricultural runoff appears to mainly affect water quality in streams and tributaries, and has little impact on the major river systems, such as the Bow and Oldman rivers. However, if agricultural impacts are not controlled, impacts on these major rivers could become significant in the future.
    5. Surface water in Alberta tends to have naturally high nutrient concentrations, with many streams exceeding phosphorus water quality guidelines under natural conditions. Most streams are therefore sensitive to relatively small phosphorus additions. While the amount of phosphorus lost from land is usually very small compared to phosphorus additions and the concentration in soil, these amounts can have an adverse impact on phosphorus concentrations in surface water.
    6. A large majority of surface runoff in Alberta's agricultural area occurs during the spring snowmelt. Even though runoff at the beginning of the snowmelt period occurs on fully or partially frozen ground, significant amounts of phosphorus are found in runoff water. Relatively few summer precipitation events result in significant runoff from fields, particularly those fields where forages are grown, or where annual crops have emerged.
    7. There is a direct, linear relationship between soil-test phosphorus levels and the phosphorus concentration in runoff water in the agricultural areas of Alberta. As the amount of phosphorus in the upper soil profile increases, so does the concentration of phosphorus in runoff water. This relationship holds true regardless of whether the soil phosphorus is from non-manured or manured soil.

    The standard composite core soil sampling depth of 0 to 15 cm which is currently recommended for producers to determine crop fertilizer requirements, is acceptable to compare actual soil-test phosphorus levels with the soil-test phosphorus limits.
    8. A direct relationship was found between soil test phosphorus levels and the phosphorus in simulated rainfall runoff from freshly applied manure and 1 year after manure application, although values of both variables were less with time. The relationship between soil-test phosphorus levels and phosphorus in simulated rainfall runoff from soils 1 year after manure application was similar to the relationship determined in other field-scale monitoring studies.

    9. Runoff volumes and concentrations of phosphorus in runoff water decreased with manure incorporation for the freshly-manured soils near Beaverlodge. However, manure incorporation did not have a significant effect on runoff volumes and phosphorus concentrations in runoff water at the two rainfall simulation sites near Lacombe and Wilson. A relatively small portion (less than 3%) of the phosphorus applied with manure was actually removed by runoff from the freshly-manured soils and even less was removed 1 year after manure application.
Soil-test phosphorus limits
    10. Soil-test phosphorus limits were determined for all agricultural land in Alberta. Using a hypothetical total phosphorus runoff water quality limit of 1.0 ppm resulted in soil-test phosphorus limits in the 0 to 15 cm layer that were:
      1. Less than 60 ppm for about 43% of the agricultural land base;
      2. 60 to 180 ppm for about 48% of the land base; and
      3. Greater than 180 ppm for about 9% of the land base.

    The results of this research present a number of challenges for producers, researchers, and policy makers in Alberta. If the calculated soil-test phosphorus limits (based on a total phosphorus runoff water quality limit of 1.0 ppm) were adopted as part of Alberta's Agricultural Operation Practices Act, producers on 1.9 Million ha of agricultural land would be required to maintain soil-test phosphorus levels that are below 30 ppm, which is half of the agronomic threshold of 60 ppm. Producers on 8.9 Million ha would be required to maintain soil-test phosphorus levels between 30 ppm and 60 ppm. Even crop producers who only apply commercial fertilizer at annual crop uptake rates would find it difficult, if not impossible, to operate under these soil-test phosphorus limits. It would prove even more difficult for Alberta's confined feeding operators.

    11. From a policy perspective, it is not reasonable to require that agricultural producers maintain soil-test phosphorus levels below 60 ppm, except in specific areas, such as flood plains and riparian zones, where the risk of runoff and nutrient movement to surface water is high.

    If 60 ppm were to become the minimum soil-test phosphorus limit (except for very high risk areas), what potential impact could this have on surface water quality? The answer is dependent on the overall development expectations for each watershed. With the exception of a few regions, most agricultural watersheds in Alberta are predominantly occupied by crop producers, who generally apply phosphorus in the form of commercial fertilizers, and only at annual crop requirements. At present, only about 5% of Alberta's agricultural land base receives manure on a regular basis, and confined feeding operations generally occupy a relatively small part of most watersheds. It is unlikely that any watershed will be developed to the extent where soil-test phosphorus levels in all Agricultural Region of Alberta Soil Inventory Database soil polygons reach the soil-test phosphorus limit. Most watersheds will have a mix; some areas where levels soil-test phosphorus exceed the soil phosphorus limit, and other areas where soil-test phosphorus levels are less than the soil-test phosphorus limit. As a result, the impact on surface water quality should therefore not be unduly compromised.
Phosphorus management
    12. It is recognized that regardless of the soil-test phosphorus limit, whether it is 40 ppm or 200 ppm, the same soil management system will have to be applied at some point in time to ensure that the limit is not exceeded.

    Ultimately, all producers will have to develop a nutrient management plan that balances phosphorus inputs to the land with phosphorus crop uptake or loss.
    Economic impacts

    13. Beef confined feeding operations generate the highest concentrations of manure per hectare of associated land. This was followed by hog operations, with dairy operations having the lowest concentrations. The most significant cost associated with manure management in Alberta is related to transportation and spreading, and ranges from $1.45/tonne to $13.33/tonne.

    14. If soil-test phosphorus limits are applied to confined feeding operations in Alberta, a substantial increase in the amount of land will be required for spreading manure. Transportation and spreading costs may increase by 24 to 128% depending on the average increase in distance that the manure needs to be hauled.

    15. Sustainable manure management in Alberta is essentially a transportation issue. There is more than enough cultivated land available to agronomically handle all of the manure generated by the confined feeding industry. More importantly, these lands would benefit from the additional nutrients and organic matter contained in manure. However, there are often large distances between the receiving land and the confined feeding operations, which can pose a significant financial burden to livestock operators.

    16. While soil-test phosphorus limits will increase manure handling costs for all confined feeding operations, the most significant concerns will occur in geographic areas of the province with large livestock concentrations. Much of the existing land base in these areas already has high soil phosphorus levels, and new un-manured land is not available within a reasonable distance. Long-distance manure transportation, or development of alternative management (composting) or uses (bio-energy) will have to be considered.
Beneficial management practices
    17. There is limited testing in Alberta to assess the economics, effectiveness, and practicality of proposed phosphorus management beneficial management practices. However, there are several beneficial management practices that producers can apply that will not only reduce the likelihood of phosphorus runoff losses, but will also improve the health of riparian areas and aquatic ecosystems.

Legislated soil-test phosphorus limits should not be implemented at this time
The adoption of soil-test phosphorus limits cannot be supported at this time, even though it is recognized that the agricultural industry will need to move towards a phosphorus strategy that balances soil phosphorus inputs with outputs. Adequate time should be provided for the agriculture industry and governments to work together to develop the technologies and follow-up programs and policies that will allow producers to effectively manage phosphorus in the long term.

In addition, further research is required to:
  • Develop and test equipment and technologies that can economically apply manure at rates that meet annual crop phosphorus requirements and reduce loss of manure nutrients during application;
  • Develop and assess environmentally effective beneficial management practices that producers can economically and practically implement; and
  • Determine maximum phosphorus limits for runoff from agricultural land and receiving streams and rivers.
The implementation of soil-test phosphorus limits may result in significant financial hardship to Alberta's intensive livestock industry, particularly the beef feedlot industry. Additional research and policy analyses are needed to develop alternate methods of managing excess manure from existing operations.

Regulation of soil-test phosphorus limits should be reviewed in 5 to 7 years to assess legislation requirements
Many jurisdictions in Canada and the United States are moving towards more regulation of the agricultural industry to minimize phosphorus losses to surface water systems. Alberta will need to assess the progress of the agricultural industry in developing and implementing a more sustainable phosphorus management strategy. Progress towards development of a sustainable phosphorus management system should be reviewed in 5 to 7 years.

The maximum soil-test phosphorus limit for Alberta should not exceed 200 ppm.
The soil-test phosphorus limits calculated in this study show that the soil-test phosphorus limits can theoretically be greater than 600 ppm for some very limited areas within watersheds. Values in this range are many times the agronomic threshold limits for crop production, and may pose significant environmental risks that are as yet unknown. A number of states in the United States including Arkansas, Delaware, Ohio,Oklahoma, Michigan, Texas and Wisconsin have identified maximum soil-test phosphorus levels of between 150 to 200 ppm. These states recognize that soil-test phosphorus levels in excess of 200 ppm have the potential for unacceptable phosphorus losses in runoff that exceed any reasonable crop requirement concerns.

A maximum allowable soil-test phosphorus level of 200 ppm (about 400 kg/ha) for Alberta will encourage more efficient use of nutrients, and will ensure that watersheds, or parts of watersheds, cannot be considered as “phosphorus disposal sites”. In addition, since manure contains many other substances in addition to phosphorus (e.g. nitrogen, bacteria, and metals), there is concern that allowing very high concentrations of phosphorus to accumulate in the soil profile increases the risk of surface water and groundwater problems by the other substances.

Design and implement management systems for high risk and sensitive landscapes.
While broad-based legislation should not be enacted at this time, special consideration should be given to high risk riparian and flood plain zones. These areas are considered to be critical phosphorus source areas and sensitive ecosystems within any watershed, and should be treated differently than other landscape zones. Higher loss rates of phosphorus applied to these landscape zones are expected, and given the close proximity to streams and rivers, a greater percentage will end up in surface water. Phosphorus should, therefore, only be applied at annual agronomic rates, which generally excludes any form of manure application. Any nutrients applied to these high risk landscape zones should be incorporated into the soil profile through banding, placement with the seed, injection, or tillage.

Develop, test, and demonstrate beneficial management practices that work in Alberta
Alberta's agricultural industry will need to shift towards a more sustainable management program that balances soil nutrient inputs with nutrient outputs in order to minimize agriculture's impact on surface water and groundwater quality. Alberta Agriculture and Food, in partnership with the agricultural industry, should accelerate the development and field testing of beneficial management practices that can be financially and practically implemented by producers, and that will be environmentally effective in reducing phosphorus losses to surface water.

Implement an education and awareness program for phosphorus management
Most Alberta producers are interested in applying beneficial management practices that will minimize agriculture's impact on the environment. Adoption of these practices is more likely to be accomplished if producers are informed of the issues and understand their options for improving management practices. Alberta Agriculture and Food , in partnership with the agricultural industry, should accelerate the development of education and awareness programs that will provide objective, science-based phosphorus management recommendations that producers can implement for their specific operations. The education and awareness program should also work with crop producers throughout Alberta to promote the significant advantages of using manure as a nutrient source.

Develop and implement a manure management incentive program for Alberta livestock producers
Implementation of soil-test phosphorus limit regulations could result in significant financial hardship to Alberta's intensive livestock industry, particularly the beef feedlot industry. Having an adequate land base to spread manure within a reasonable distance from the feeding operation is already a challenge for many confined feeding operations. If the industry is forced to move towards a phosphorus-based manure management program, even greater land base challenges will occur. These challenges will be greatest for those geographic regions where the historical development of confined feeding operations resulted in feeding operations being located relatively close to each other. Providing a transitional funding support program will reduce manure applications on existing land by promoting the transportation of excess manure greater distances. In addition, it will promote the significant benefits of manure to a greater area of cropland in the province, and reduce overall phosphorus losses to streams and rivers.

Alberta Soil Phosphorus Limits Project: Index to Final Report Volumes

Volume 1: Summary and Recommendations

Volume 2: Field-scale Losses and Soil Limits
  • Relationships Between Soil-test Phosphorus and Runoff Phosphorus in Small Alberta Watersheds
  • Calculation of Soil Phosphorus Limits for Agricultural Land in Alberta
Volume 3: Soil Sampling, Manure Application, and Sorption Characteristics Volume 4: Economics and Management Volume 5: Background Information and Reviews Research Publications

The following papers have been published in peer-viewed journals based on research work from the Alberta Soil Phosphorus Limits Project.

Casson, J.P., Bennett, D.R., Nolan, S.C., Olson, B.M., and Ontkean, G.R. 2006. Degree of phosphorus saturation thresholds in manure-amended soils of Alberta. Journal of Environmental Quality 35:2212-222.

Little, J.J., Nolan, S.C., Casson, J.P., and Olson, B.M. 2007. Relationships between soil and runoff phosphorus in small Alberta watersheds. Journal of Environmental Quality 36:1289-1300.

Volf, C.A., Ontkean, G.R., Bennett, D.R., Chanasyk, D.S., and Miller, J.J. 2007. Phosphorus losses in simulated rainfall runoff from manured soils of Alberta. Journal of Environmental Quality 36:730-741.

Nolan, S.C., Little, J.L., Casson, J.P., Hecker, F.J., and Olson, B.M. 2007. Field-scale variation of soil phosphorus within small Alberta watersheds. Journal of Soil and Water Conservation 62: 414-422.


The project team expresses its appreciation for the significant amount of funding that was provided by: the Agricultural Funding Consortium, with contributions from the Alberta Livestock Industry Development Fund, the Alberta Crop Industry Development Fund, and the Alberta Agricultural Research Institute (project number 2003C0057R); the Canada Adaptation and Rural Development (CARD) Fund; and the Alberta Environmentally Sustainable Agriculture (AESA) Council.

Funding and resources were also provided by Alberta Agriculture and Food (Resource Management and Irrigation Division, Technical Services Division, Animal Industry Division, and Plant Industry Division).

Appreciation is expressed to the many agricultural producers throughout Alberta for their support in allowing project staff to set up and operate monitoring stations on their land.

The authors are very grateful to Janna Casson, Frank Hecker, Andy Jedrych, Andrea Kalischuk, Joanne Little, Sheilah Nolan, Gerald Ontkean, and Barb Shackel-Hardman for reviewing earlier drafts of the Summary and Recommendations Report and for providing many valuable suggestions.

The Authors are particularly grateful to Bonnie Hofer of the Irrigation Branch, Alberta Agriculture and Food, for designing and coordinating the covers for the five volumes and the layout of Volume 1.

Contributions to the project were provided by the following staff from Alberta Agriculture and Food, Agriculture and Agri-Food Canada, Alberta Environment, and the University of Alberta.

Mohamed Amrani 1,2 Frank Hecker 1,5 Tim Martin 1,2 Lawrence Schinkel 1,5
Anne-Marie Anderson 2,3 Kim Hodge 2,6 Dennis Mikalson 1,5 Annette Svederus 1,2
Rod Bennett 1 Allan Howard 1,2 Sheilah Nolan 1,5 Douwe Vanderwel 1,2
Janna Casson1,5 Andy Jedrych 1 Barry Olson 1 Callie Volf 4,5
David Chanasyk 4,5 Andrea Kalischuk 1,5 Gerald Ontkean 1,5 Ralph Wright 1,2
Sandra Cooke 1,2 Larry Kwasny 1,2 Brent Paterson 1,7 Jamie Wuite 1,2
Tom Goddard 1,2 Joanne Little 1,5 Murray Peters 1,5  
Dan Heaney 1,2 Paolo Mantuna 1,2 Sandi Riemersma 1,2  
1 Alberta Agriculture and Food; 2 Phase 1 only (1999 - 2002); 3Alberta Environment;
4University of Alberta; 5Phase 2 only (2002 - 2006); 6Agriculture and Agri-Food Canada; 7Project chair.

Two Steering Committees were established during the course of the project. The Steering Committee members provided valuable advice and direction to the Technical Working Group. The support from the livestock and crop industry members is greatly appreciated.

Steering Committee (1999 to 2001)
Doug HallAlberta Environmental Sustainable Agriculture Council
Dan HeaneyAlberta Agriculture and Food
Bill MackayW.C. Mackay and Associates
Barry OlsonAlberta Agriculture and Food
Brent Paterson (Chair)Alberta Agriculture and Food
Barb Shackel-HardmanAlberta Agriculture and Food
Gary TelfordAgriculture and Agri-Food Canada
Dave TrewAlberta Environment
Joyce Van DonkersgoedIntensive LivestockWorking Group

Steering Committee (2004 to 2006)
David ChanasykUniversity of Alberta
Ray GrimsonLakeside Farm Industries Ltd.
Mike HartAlberta Egg Producers
Adrian JohnstonPhosphorus and Potash Institute
Bruce KonynenbeltAlberta Pork
Erasmus OkineUniversity of Alberta
Rients PalsmaAlberta Milk
Brent Paterson (Chair)Alberta Agriculture and Food
Barb Shackel-HardmanAlberta Agriculture and Food
Stuart ThiessenAlberta Beef Producers
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This information published to the web on December 31, 2007.
Last Reviewed/Revised on March 28, 2017.