1. Soil test: When soil test P is at or below the Tri-State maintenance level (46 ppm Mehlich III or 30 ppm Bray I) those fields meet or are below current Annex 4 loading recommendations of 0.3 kg/ha (0.27 lbs/acre).  Based on recent surveys, roughly 75% of all producers regularly soil test. Regular soil testing (once every 3 years and less than 25 acres per sample) and adherence to the Tri-State Recommendation based on the soil sample analysis will reduce the potential for P loss in both surface and tile pathways.

2. Application timing: Application timing has two aspects, time between application and rainfall, and time of year. The longer the time between application and rainfall, the less the loss of P. With respect to time of year, the largest losses of dissolved P were measured during the fall and winter. Ohio Senate Bill 1 now eliminates the application of fertilizer (commercial or manure) on frozen and snow covered ground, addressing the potential for these large losses. Moderate losses were measured when application was made at or near planting. The least losses were measured when fertilizer was applied after wheat harvest. This is the period when large runoff and erosive rainfalls are least expected.  Based on the preliminary findings, we are recommending introducing small grains back into the rotation and applying fertilizer following harvest of small grains. While not popular from an economic standpoint, small grains do offer significant soil health benefits and provide a window of opportunity for applying P and minimizing loss.

3. Subsurface placement:  Incorporating fertilizer with the soil through banding or injection but also light tillage significantly reduces the potential of loss through both surface and subsurface pathways. Based on the edge-of-field studies, the recommendation is to apply P into the soil through banding or injection or incorporate through light tillage.

4.  Disconnection of hydrologic pathways:  P moves with the water. Disconnecting the hydrologic pathways minimizes the amount of P going downstream. Three recommended practices for disconnecting the hydrologic pathways are: drainage water management (DWM), replacing surface inlets with blind inlets, and increasing soil organic matter.  DWM artificially raises the tile outlet elevation during periods (fall/winter) of the year when drainage is not as critical. Blind inlets refer to replacing surface inlets with a reverse leach field reducing surface flow into the tile system. Increasing soil organic matter promotes water storage in the soil profile. For every percent of organic matter in the soil, roughly one inch of water can be stored. Holding water back and storing water in the soil profile results in less water and associated P moving offsite and into surface ditches.