You can use the Agronomic Balance and the Crop Removal Balance for planning a phosphorus fertility plan for a field.
The Agronomic Balance is based on making sure there is enough phosphorus in the soil to provide the growing crop with enough nutrients to achieve the desired yield and crop quality. The Agronomic Balance considers the existing amount of nutrient in the soil and the likelihood of a financial benefit for additional phosphorus.
Make sure that the amount of phosphorus from all sources is not 17 kg of phosphate/ha/year (15 lbs. phosphate/acre/year) over the recommended requirements for that crop.
The Crop Removal Balance is based on ensuring that the crop can take in the added phosphorus, therefore limiting the amount of phosphorus left over after harvest to build up in the soil.
It is a good management practice to make sure that the amount of phosphorus added to the soil does not exceed 78 kg phosphate/ha/year (69 lbs. phosphate/acre/year) more than is removed from the soil when the crop is harvested. This will limit the buildup of phosphorus in the soil. The accepted buildup level is 2 mg/l of soil per year.
For some crops grown on low testing soils, the Agronomic Balance will allow for more P2O5 application to a given field. For most crops and in higher testing soils, the Crop Removal Balance will be less restrictive.
AgriSuite will evaluate historical practices to make sure nutrient applications do not exceed regulatory limits. The software also uses some conservative estimates for future practices to make sure that the current nutrient application does not lead to an exceedance in the future.
When a farm is required to follow a nutrient management plan, the regulation allows for the greater of either:
When evaluating the nutrient loading in a nutrient management strategy, OMAFRA must be sure that the farmer is able to responsibly manage the manure generated at their operation.
Experience has shown that different livestock species lend themselves to unique cropping patterns, and these cropping patterns result in varying amounts of nutrient use. For example, a dairy farm often grows corn silage and hay where much of the above-ground portions of the plant are harvested. This will remove more nutrient from the field than harvesting only the grain portion of the crop. The following chart, developed from several case studies across the province, provides a guide for determining whether a farm has an adequate land-base to manage the manure they produce. If the farm you are working with has a higher nutrient loading, you may be asked for more documentation regarding manure management.
| Species | Nutrient Loading Rate (NU/ha) | Nutrient Loading Rate (NU/acre |
|---|---|---|
| Dairy | 3.1 | 1.25 |
| Poultry | 2.0 | 0.8 |
| Other | 2.5 | 1.0 |
If you are asked to provide a nutrient balance when developing a nutrient management strategy, you can approach it in two ways.
If the one year or five-year NMP shows a P205 surplus higher than the regulatory maximums, nutrient loading is a concern. You will need to consider transferring some of the manure off the farm unit and/or finding more land to apply the manure on.
Reviewed 09/14/2023