Significant Scope for Improvement of Soil Acidity Management in US Croplands

Robust soil pH management in agricultural lands is critically important for crop yields and can lead to significant greenhouse gas reductions in agricultural systems. However, costs and logistical constraints can limit the extent to which agricultural soil pH is actively managed. We develop two new estimates of soil pH across the conterminous United States using empirical Bayesian kriging and random forest approaches. We compare these estimated pH values against a new dataset of the agronomically recommended pH at a county level, defined by state-specific soil pH recommendations for the most prominent crop in each county. We estimate between 44–55% of cropland acres in the conterminous United States are below agronomically optimal soil pH. We couple these new estimates with high resolution pH data from six agricultural sites. We find large variability in soil acidity at the field scale, indicating that regional mapping efforts likely underestimate the need for soil deacidification.