1. Speculation on an Equation for Stratification: How Reliably Can We Estimate Soil Test Values at Different Depths?

The depth to which soil is sampled in a field impacts measured soil test values. However, across the West, depth of soil sampling can vary by state, region and cropping system. What if we're interested in comparing crop responses to fertilizer application across a large scale? How do we reconcile trials that are sampled at different soil depths? This study was part of the Fertilizer Recommendation Support Tool (FRST) project, with the goal to develop equations that allowed comparison... S. Culman