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Crop Corner – Responsible Phosphorus Management

March 06, 2021

Elevated phosphorus levels in Lake Erie have become a hot topic of discussion. Although there are many factors leading to excess phosphorus in the lake, agriculture contributes significantly to the pollution. Haldimand/Niagara farms are also facing soil phosphorus levels that have been severely depleted. Proper management of phosphorus would significantly reduce the volume entering the lake, but also economically increase soil test values and crop yields. Farmers should be proactive in minimizing the amount of phosphorus leaving their fields. When phosphorus leaves a field, the money invested in the nutrient is also lost. Proper management will limit the amount of phosphorus that leaves the field, therefore not only helping the environment but also your bottom line. If proactive measures are not taken, legislation will eventually mandate farming practices. 

Manure is one of the biggest culprits of phosphorus entering the lake. A concerted effort needs to be made to manage manure better. Manure needs to start being treated like the valuable commodity that it is. Spreading manure on snow and frozen ground leads to a high rate of runoff, carrying nutrients with it. A farmer would not apply commercial fertilizer in conditions where significant runoff would occur, so why do it with manure? Manure is an excellent source of expensive nutrients, and it should be treated in such a way to maximize nutrient use.

One of the easiest ways to manage phosphorus better is through proper application. Phosphorus should never be surface applied in late fall or winter, unless it is thoroughly incorporated. Phosphorus does not move through the soil easily. When surface applied, it will remain there for an extended period of time and be susceptible to runoff. Cover crops and residue will reduce runoff and erosion, and are great tools to keep phosphorus in the field. Application of phosphorus to bare ground, prior to winter, should be limited. 

No-till or minimum-till situations require different strategies since phosphorus cannot be incorporated through tillage. Banding works best in these situations. Phosphorus is readily tied up by interactions with the soil. When this happens it cannot readily be accessed by the crop. Banding reduces this affect by concentrating phosphorus in a narrow band, reducing the volume of soil it comes into contact with. The ROI of banded phosphorus is much greater than broadcasting. Phosphorus should be banded whenever possible. One of the best ways to band phosphorus is during wheat planting. Large amounts of phosphorus can safely be placed with wheat seed. Corn can also have a lot of phosphorus fertilizer placed in a band beside the seed, while soybeans will only tolerate a small amount. Having a rotation with less soybeans will present greater opportunities to band phosphorus.  Air Seeders can also be utilized as a dedicated fertilizer application tool. Despite the slightly higher cost and time need to run a seeder over the field, it has significant benefits compared to broadcasting. The fertilizer is readily available in a band, it is safely placed below the soil surface, and application will be highly precise.

Several tools exist to safely apply phosphorus, it just takes the planning and commitment to utilizing them. If you would like to change crop management practices for better environmental stewardship and profitability, contact your Clark Agronomist for advice.