A new scientific study indicates that the fertilizer you spread on lawns and gardens today may still be present 80 years from now. The study, published in the Proceedings of the National Academy of Sciences, is the first to measure how long nitrogen-based fertilizers persist in the field.

This study took a form of nitrogen known as nitrogen 15 (called an “isotope”) and added it to the more common nitrogen 14 in the soil. For thirty years, the scientists grew beets and winter wheat. They found that the nitrogen 15 persisted in the soil and they calculated that some of the nitrogen used at the beginning of the trial would still have been present in 80 years.

This provides an explanation of how commercial clients can reduce their use of fertilizer, and still have nitrogen runoff years later. However the study provides no key or method for unlocking that fertilizer in the soil and having plants make more thorough use of it.