Significance of agricultural row structure on the microwave emissivity of soils

A series of field experiments was conducted to extend the database available for verifying agricultural-row-effects models of emissivity. Observations were made using a truck-mounted, 21-cm, 1.4-GHz passive microwave radiometer for a range of soil moisture conditions on three bare soil plots: a flat control field, a furrowed field with row height 15 cm and row spacing 75 cm, and a furrowed field with row height 30 cm and row spacing 90 cm. An examination of model predictions for the test conditions indicated that although the composite roughness model tended to overestimate the effect of row structure on emissivity, it reproduced the observations fairly well. Both simulation results and the field measurements indicated that if an error of ±0.03 in estimating emissivity, could be tolerated, then a reliable prediction of equivalent smooth field emissivity can be made for furrowed fields with row-height/row-spacing ratio less than 0.2, which encompasses most dry-land agricultural planting practices