Some Physical Factors that Influence Soil Erosion and the Influence of Aggregate Size and Stability on Growth of Tomatoes

Abstract The object of this investigation was to obtain quantitative laboratory data on the primary effects and interactions of aggregate size and stability, rainfall rate, soil slope, and surface condition on soil erosion by water. Sharkey clay was treated at three rates with a modified vinyl acetate‐maleic acid compound to obtain three degrees of aggregate stability. The three soil samples were then separated into five size classes and subjected to the action of water under three different rainfall rates, three different slopes and two different surface conditions. In this study size of aggregates had the greatest influence on the erosion of soil. As size was decreased from 1,000 to 500µ size, there was a slight increase in erosion but a much greater increase occurred as size was decreased further. Surface condition, rate of rainfall and aggregate stability have a significant influence on all aggregate sizes, but slope influenced only the erosion of small aggregates. The first order interactions were significant for small aggregates but the higher order interactions were not significant for any size class. When 30% of the aggregates were water stable, the dry weight of both shoots and roots of tomato plants increased as the size of the aggregates increased. When 45% of the aggregates were water stable, however, the dry weight of both shoots and roots increased as aggregate size decreased. The integrated effect of the large aggregates of lower stability was the same as small aggregates of higher stability. It is inferred that the former reduced in size during the growth of the tomato plants. Small aggregates of the lower stability reduced in size to such an extent that the moisture intake and transmission were impaired.