Phosphorus in the Lake Erie Basin: How Can We Better Manage Our Fertilizers?.

In recent years, algal blooms have become an increasing nuisance, and in large part have been blamed on agricultural contributions. Over the last three decades, conservation efforts have been focused on the adoption of no-tillage or conservation tillage practices. These efforts have worked to decrease total phosphorus loading; however, soluble phosphorus (the most bioavailable component of phosphorus) loadings have increased in recent years. Indeed, if improperly managed, continuous no-till will result in surface applications of phosphorus fertilizers with no incorporation, which in turn leaves the fertilizer vulnerable to losses through runoff. Conventional wisdom suggests that phosphorus only leaves fields through surface runoff processes; however recent results suggest that almost 50% of the phosphorus that leaves fields in the Lake Erie Basin is through the subsurface drainage tile network. Many farmers have provided anecdotal evidence that no-till fields have healthier soils, and thus can be farmed with lower soil phosphorus levels. When yield maps are coupled with maps of soil test phosphorus level in a field that varies from 11 to 92 kg/ha, there is no correlation between soil test phosphorus and yield for either soybean or corn. This particular farmer uses no-till practices and applies a starter fertilizer containing phosphorus in the seed row. In other applications, high end nutrient management planners alter seeding rates, hybrids, and nutrient application rates based on soils and topography within the field. Phosphorus loadings contribute to Lake Erie eutrophication; however producers are learning to better manage phosphorus to optimize crop production with environmental protection.