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
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.