Agricultural Field Shape Descriptors As Predictors of Field Efficiency for Perennial Grass Harvesting: an Empirical Proof

Perennial grasses can serve as a material for bioenergy, biomaterials, animal feed or bedding, or other purposes. Researchers suggest that planting perennial grasses on marginal parts of agricultural fields can provide sustainability benefits; however, planting the marginal areas may result in complex shapes and changes to field areas and thus be difficult to harvest. Harvesting costs can be a limiting factor in widely adopting perennial grasses, so the more efficient the machinery operations are, the more viable perennial crops become for farmers and bioenergy stakeholders. This study explores the relationship between field shape and size and empirically derived harvesting efficiency to support assumptions relative to predicting harvesting cost, greenhouse gas (GHG) emissions, labor demands, and other factors impacting willingness to cultivate energy crops, which can be impacted by field efficiency. Switchgrass (Panicwn virgatum L.) mowing data were used in the study. The regression analysis showed that the natural log transformation of the perimeter-to-area (P/A) ratio was the most accurate predictor for field efficiency (FE) (R-2 = 71%) among shape descriptors as it takes both field size and shape into account. Optimizing field designs that combine annual crops and perennial grasses for lower P/A ratios will decrease operation costs and, thus, improve the rate of practice adoption of perennial grasses in agriculture.