Utilization and limitations of soil health metrics in Missouri corn production decisions

Abstract

Soil health benefits are widely acknowledged but empirically-vetted connections to agronomic outcomes remain absent. Therefore, recommendations for on-farm soil health assessments and interpretation remain ambiguous. Empirical connections to two major outcomes remain absent, specifically row crop productivity and fertilizer recommendations. This dissertation investigates potential benefits from incorporating soil health indicators with established phosphorus (P) and potassium (K) fertilizer recommendations, evaluates links between soil health indicators and corn grain productivity, and identifies optimal sampling depths and regional sensitivity to common conservation practices for seven unique soil health indicators. All results and conclusions derive from a dataset collected over three seasons (2018-2020) including 446 sample locations collected from 101 Mid-Missouri commercial row crop systems. Current P and K fertilizer recommendations accurately identified where fertilizer improved yield with 42 and 34 percent accuracy, respectively. No significant or measurable benefit occurred from incorporating soil health indicators with established P and K soil nutrient analysis when identifying nutrient deficiencies. Investigations into general productivity discovered an empirical relationship between potassium permanganate oxidizable carbon (or POXC) and grain yield. This relationship identified a POXC value of [greater than] 415 mg kg soil-1 where corn productivity was optimized. Further, POXC outperformed all other established soil analyses in predicting corn grain yield. Finally, regional sensitivity analysis of soil biological indicators of soil health identified important environmental and soil properties to consider when interpreting soil health assessments in Mid-Missouri. Recommendations were unique for each soil health assessment, with specific conservation practices and optimal sampling depth. In total, these results provide the needed groundwork connecting soil health with agronomic outcomes to support on-farm soil health interpretations.