P-Based Manure Mangement Tools: Strategic Vs. Tactical.

Dr. Bundy’s career spanned the evolution of phosphorus (P) management from a focus solely on agronomic concerns to our initial attempts to address water quality goals. 

Twentieth century P management primarily focused on strategic decision making to meet agronomic goals; soil testing assessed the soil nutrient status for plants as the basis for P fertilizer application.  Soil testing technology is easily implemented into a work-force with minimal training and soil testing interpretations are conveyed at a level most farmers and farm employees can understand. 

Early in the twenty-first century P Indices were deployed in most US states as a strategic planning tool to identify fields or P applications that were likely to result in high P losses and/or P concentrations in edge-of-field runoff.  Unfortunately, the use and interpretation of P Indices is typically much more technically demanding than soil testing.  Many P Indices require an estimate of erosion derived from the USDA Natural Resource Conservation Service (NRCS) decision support tool, RUSLE2.  Use of this tool requires extensive training that few farmers and manure applicators possess.  Phosphorus Indices remain largely a specialized tool used by animal feeding operations that are required to use them because of regulations or as a requirement of voluntary cost-share programs.

High profile events such as the Toledo, OH drinking water ban emphasize that scrutiny of agricultural P management will likely intensify in the future.  As a group we must revisit our strategies for managing manure and fertilizer P.  I put forth two challenges:

1. Revisit our soil testing recommendations and integrate an awareness of water quality concerns into the rationale and risk assessment of target soil test levels;

2. Identify appropriate strategies for farmers and their employees to address both strategic and tactical decision making needed for limiting P applications’ impact on water quality.