EFFECT OF CLAY CONTENT AND AGGREGATE SIZE ON AVAILABILITY OF SOIL WATER TO TOMATO PLANTS

Abstract

Water availability in St. Bernard sandy clay loam, Chateauguay silty clay loam and Ste. Rosalie clay soils was determined. The criterion of water availability was growth rate, measured as an increase in leaf area as a fraction of existing leaf area, of tomato plants grown in a controlled environment room. At a given soil suction, growth rate was higher in the two soils high in clay content than in the medium textured St. Bernard, and was dependent upon aggregate size. Differences in hydraulic conductivity and water retention properties accounted for most but not all the differences in growth rate–soil suction relationships. In the two soils of higher clay content, growth–soil suction relationships of undisturbed soils were not materially different from those in sieved aggregates.Oxygen diffusion rates at least as low as 10 × 10 −8 g cm −2 min −1 over short periods were adequate for maximum growth and did not appear to influence availability of water.