Temporal Frequency of Soil Test Information Effects on Returns to Potassium Fertilization in Cotton Production
Harmon, X.L., C. Boyer, D. M. Lambert, and J. A. Larson.  2017.  Journal of Agricultural and Applied Economics, 49,2: 251-272.

Abstract:
Little research exists on the optimal temporal frequency between soil tests, given empirical data on potassium (K) carryover and its interaction with cotton yield. We evaluate how decreasing the temporal frequency between obtaining K soil test information affects the net present value (NPV) of cotton production. Monte Carlo simulation was used to determine NPV for cotton production using five soil test schedules ranging from soil testing annually to every fifth year. NPV of returns to K was maximized at $7,580/ac. when producers updated soil testing information every 2 years, which was $2/ac. per year greater than annual soil testing.