Protocol for Estimating Whole-Field Biomass Yield in a Standing Crop.

We developed an in-field method for estimating bioenergy sorghum biomass yields in a standing crop. We observe that a small number of plant yield samples gathered from spatially convenient field positions provide sufficient information to reliably estimate whole-field yields.   Our concept is grounded in spatial statistics where rapid, non-destructive biomass measurements are recorded at uniformly dispersed positions throughout a production field.   We predetermine and geo-reference a minimum of sixteen sampling positions across a field, and at each point measure and record basal stalk diameter, plant canopy width per row, average plant height, and number of plant stalks or stems per sample area.  Our test sample area dimension per position was seven meters of row for each of two adjacent rows, providing fourteen meters of row per sample position.  Each set of plant measurements is combined with a simple formula to provide one numerical value per sample position; the calculated value is closely correlated with plant biomass yield and serves as an estimate of yield magnitude.  Conceptually, a set of yield magnitude estimates for a given field functions much like an over-sampled variable or covariate where the variable in question is biomass yield.  Biomass yield measures may be performed at superior and/or inferior sample positions.  A whole-field biomass yield estimate is calculated for each yield sample and the whole-field average is estimated.  We present validation data that illustrates the reliability of our estimation method, and discuss expansion of this technique to address ground-truthing remotely sensed data.