PHOSPHORUS – A FRIEND OR A FOE?
Once referred to as the "breadbasket of the world," the Canadian Prairies have faced a number of growing environmental challenges recently everything from drought to flooding, to climatic stresses and even more recently, climate change. Agriculture pushes each year towards more efficient practices for increasing production and yields all while adopting and protecting sustainable stewardship practices. But "come rain or shine," one element tends to remain the same in the Prairies - the amount of phosphorus we have, and we typically are deficient. Science can easily attribute the deficiency to the naturally occurring low levels already present in Prairie soil or perhaps attribute it to the phosphorus already tied up in chemical or biological processes where it's not easily nor readily available for crops. Either way depending on the amount of crop production required and the amount of phosphorus already available, it could be easy for some farmers miss the match between the amount removed and their supplementary applications. Phosphorus, a Farmers friend In agriculture, phosphorus can be a farmer's best friend since it is essential for crop production. Easily cautioned however if applied at an insufficient rate, poor time or even at an improper place, Phosphorus could become a serious foe and in a short amount of time. Excessive amounts of phosphorus have been known to deteriorate and impact surface and groundwater sources by interfering with the overall nutrient balance in the water quality, eventually encouraging and contributing to excessive algae growth and eutrophication (nutrient rich waters) as a byproduct. Geographically speaking areas of large, flat, low-lying fields, as characterized in most of the Prairies tends to have a lower risk for water erosion especially when combined with the "pothole" topography. Snowmelt however, can cause concerns of flooding and add to an increased runoff potential through the transportation of phosphorus. Finally identifying the source of phosphorus is yet another important factor, whether it is from vegetation, or from fresh or frozen manure, when dealing with an abundance of snowmelt. Ecological water quality and phosphorus Most of us are familiar with the idiom "when it rains it pours" and that seems to be the case when talking about phosphorus. It's a challenging element in a best management practice because trying to control phosphorus loss can be a difficult task when given the phosphorus deficient landscape of the Prairies combined with our naturally eutrophic waters. Hence why phosphorus in terms of ecological water quality is typically coined a potential "foe." Especially near Lake Winnipeg watersheds where phosphorus is a well-known producer of green eutrophic waters which affects the overall health of the lake structure and function. Simple Solutions for the Short-Term So how can Farmers effectively manage phosphorus for the environment, for their crops, and also ensure compliance within the Save Lake Winnipeg Act? Let's consider some best management practices in efforts to identify some simple solutions. Vegetative buffer strips have been effective in reducing phosphorus runoff in much of the Prairies. Although sometimes controversial research suggests that buffer strips when used as a BMP may be more effective for rainfall runoff rather than snowmelt runoff (Sheppard et al. 2006 Can. J. Soil Sci. 86:871-884). Regardless it remains a beneficial practice. Compliance in applying public policies associated with the Save Lake Winnipeg Act assists in reducing nutrient loadings, as well. Farmers can also try to balance their phosphorus applications with their phosphorus removal rates and in doing so can minimize or avoid any excessive soil test phosphorus levels. Check your soil pH, and record and monitor your soil samples. Soil pH is a primary determining factor for phosphorus availability. So try to balance low pH and high pH in the soil, because soils with a neutral pH tend to allow more phosphorus to remain (held) in soil solution. Ensure healthy soil biology including the use of microorganisms especially for the soils surrounding the root systems. Prevent erosion where possible on slopes since most phosphorus is found within the top six inches of the soil. Remember phosphorus moves with water so try to minimize phosphorus transport to nearby watercourses by reducing runoff potentials, leachate availability, and soil erosion. Monitor, record, and assess within the same year and even within the same field perhaps, your crops response to phosphorus since it is very sensitive to environmental conditions. Try to protect and restore nearby wetlands since they are Earth's natural filters. It is suggested by conservation experts that the potential impacts of climate change may affect the applicability of our floodplain approach of a "once in a 100-year flood" thereby also increasing the need for wetlands in the future. Finally, tip of my hat off to the farmers who are challenged with phosphorus and have been working with it sustainably over the years. Whether you consider it as a friend or foe, thanks for your continued patience while working to balance it. ________________________ Diana Tyner (M.Sc.) is an environmental advisor, water guru, and certified CSA greenhouse gas quantifier. She works with Canadian business, government, and non-profits to advance, science, agriculture, and economics.Read more blog post from Diana here