Strategies for Reducing Application
To make the best use of existing soil phosphorus, two main strategies can be used together.1
First, reduce phosphorus fertilizer applications until soil phosphorus levels fall to a critical point where yield loss becomes a risk. This strategy leverages the phosphorus already in the soil, which can support good crop yields for up to ten years or more. Partial reductions are often more practical than stopping fertilizer completely, as they lower the risk of yield loss.
Second, improve cropping systems to use phosphorus more efficiently. This means finding ways to help crops perform well even when soil phosphorus levels are lower. Better phosphorus management allows crops to make better use of the phosphorus already in the soil.
Tools for Utilizing Soil Phosphorus
Simply cutting back on new phosphorus applications does not fully use all the excess phosphorus in the soil. To make use of these reserves, it's necessary to unlock the less available forms of phosphorus. Tools that can help include:
- Soil test: Tailor phosphorus application rates based on soil tests taken at least every 3 years.
- Precision management: Using precise application techniques can make phosphorus use more efficient. Using recycled phosphorus sources and manures can also help and will boost soil microbial activity.
- Plant breeding: Developing crops with better root systems or lower phosphorus needs can improve the efficiency of phosphorus use.
- Fostering soil microbes: Practices such as reducing soil disturbance and using diverse cover crops can support beneficial microbes that help plants access more phosphorus.1
Challenges remain, including variations in how much phosphorus crops recover and how long it takes for phosphorus levels to stabilize in the soil.2 Current testing methods can't always identify different phosphorus forms, and other soil components, like soil organic carbon, also affect phosphorus availability.3
Soil Labs
If you want to test your soil, there are many options available. Here are labs that service Michigan:
Resources: