As you figure out how much fertility to add to your fields this year, make sure you're including nitrogen that is left over from previous cover crops and compost / manure applications. You may need less nitrogen than what is recommended on your soil test. What is a nitrogen credit? There are two basic categories of fertilizers: inorganic and organic. Organic in this case does not mean USDA certified organic, but rather any fertility source that is bound in carbon. Organic sources of fertility include things like manure, composted manure, compost, cover crops, fish meal, etc. When nitrogen is bound in an organic form, it takes a while to mineralize, or become usable by plants. In some cases, it can take 1-2 years. Farmers should take this into account when making fertility plans to avoid over-fertilizing. Calculating nitrogen credits from cover crops If you planted a cover crop in the fall, you are likely going to receive some nitrogen from it this spring. Legume cover crops can pr...
