Heavy rainfall events are a prime contributor to agricultural nutrient losses, with water transporting nutrients to surface water bodies. Recently applied mineral fertilizers on the soil surface are at particular risk for transport as moving water can carry fertilizer particles, as well as quickly convert nutrients into dissolved forms. Commercial fertilizers are designed to be highly water soluble for optimal agronomic performance, but that also means they can easily dissolve into water and carried from fields. Surface application of fertilizers is a viable agronomic practice, and research indicates 7-10 days are needed before natural chemical processes bind fertilizers to soil particles. Prior to this binding, fertilizers are susceptible to transport by rain events. Tillage can speed the process of binding fertilizer nutrients to soil particles, as well as removing nutrients from the soil surface and direct interaction with rain. While tillage itself increases potential erosion risks, research results have indicated when a moderate rainfall event occurs within 24 hours of a nutrient application, nutrient losses are decreased if the nutrients have been incorporated. Timing nutrient applications so that surface applied nutrients aren’t susceptible to runoff is an impactful nutrient loss mitigation strategy that improves agronomic efficiency at the same time. When heavy rains are forecasted, surface applications should be avoided, with particular care in avoiding applications to sloping fields where runoff can be exacerbated. Prioritizing applications in fields where tillage operations are planned is helpful as well. Today in the Lake Erie basin, upwards of 80% of nutrient losses are believed to stem from 10% of the nutrient loss events. By considering weather forecasts and avoiding the application of nutrients before high intensity rain events, a significant cause of nutrient losses can be avoided.
