Large intact soil slabs for studying the effects of soil and plant properties on surface runoff

A system is described for the collection and preparation of large (0.5 t) slabs of soil from the held for use in studies of surface runoff. Sample collection involves insertion of a steel-cutting frame to the chosen depth, followed by under-cutting by a hydraulically driven base-plate. In the laboratory, the slab is mounted on a frame with an adjustable slope. The cutting frame is replaced by a retention box that allows monitoring of surface runoff and soil water content after applications of wastes and simulated rainfall. Measurements of flow rate, velocity and depth on the soil. surface enable characterization of surface hydraulic resistance. Nondestructive measurements of soil surface roughness can be made before and after runoff tests, and soil structural attributes are determined after collection of appropriate intact samples from the soil slab. The general applicability of the slab collection and monitoring methods are discussed in the light of experience gained with both grassland soils and arable soils. (C) 1999 Silsoe Research Institute.