Grid Sampling or Conventional Sampling to Guide Site Specific Recommendations of Phosphorus and Potassium in Small Crop Fields in West Virginia.

Grid sampling cause significant nutrient redistribution (less in some field areas, more in others), relative to conventional (single composite for entire field) sampling.

We hypothesize that not all the fields need to be grid sampled.

Materials and Methods

33 fields between 5 and 47 acres where sampled (average size 21 acres)

The grid cell size varies between 1 and 2.25 acres (average of 1.8 acres)

33 fields with 3 to 16 cells (average of 10 cells/field).

Soil samples were analyzed for soil test P (STP) and soil test K (STK) by Mehlich I extraction; “Field-average” STP and STK was independently acquired by conventional soil sampling (single composite field sample).

Assumptions: 1 to 2.25 acre grid size may not capture all management-relevant variation

Conclusions:

Grid sampling was usually beneficial, but pre-sampling to identify candidate fields is useful.

Grid sampling tends to benefit most fields as nutrient addition/nutrient removal brings average STP and STK values close to recommendation thresholds.