When compost is over-applied, excess nitrogen and phosphorus can make their way to nearby bodies of water through leaching and runoff and harm the environment.
Farmers avoid this by testing their compost, much like they test their soil. Then, they use the compost's nutrient content to calculate the amount to apply based on the needs of the crops they grow. You can use the same approach in your vegetable garden.
To do this, you'll need:
- A soil test report to understand the amounts of nutrients already in your soil, and
- A compost test report to know what nutrients your compost will contribute.
Most soil testing labs also analyze compost. For example, the Penn State Agricultural Analytical Services Laboratory offers compost testing services. You can learn more and submit a sample by visiting compost testing.
Compost is commonly applied based on the plant's nitrogen or phosphorus needs. But phosphorus is often over-applied when compost rates are based on nitrogen. We'll focus on the amount of compost to apply based on the plant's phosphorus needs. This approach helps keep your plants productive while protecting the environment.
Source : psu.edu