THE OCCURRENCE AND PREDICTION OF CLODS IN POTATO RIDGES IN RELATION TO SOIL PHYSICAL PROPERTIES

Abstract

Summary Clod crushing resistance, bulk density, moisture content, and size distribution, together with fifteen bulk soil physical properties, were determined at thirty sites. Regression analyses indicated that the plasticity index of the soil is the principal property affecting both the clod crushing resistance and the yield of clods. Other less closely related properties are not always consistent in their effect between clod size ranges. A‘clod factor’ was derived from the product of the clod crushing resistance and the weight of clods in the ridge for each soil. The clod factor is linearly correlated with plasticity index ( r = 0·587, P = 0·002) and a clod factor > 1000 was found for soils with a plasticity index greater than about 5. Harvest observations suggest that where the clod factor exceeded 1000, the efficiency of a mechanical potato harvester was reduced.