Soil Hydrology Overview

This data reflects both the quality of the soil structure, the amount of water available for growth and the ease by which these soils are able to be irrigated. The data indicates how much water is available for vigorous tree and fruit growth, as well as how much water is available for tree maintenance and survival. This data can also be used to better schedule irrigation, and compare irrigation requirements between soils.

The topsoil (A1 horizon) appears to be moderately compact with a bulk density of 1.37 g/cm³, however all other measures indicate the a1 horizon to be a very well structured soil. The saturated hydraulic conductivity at 500 mm/hr is excellent, and the drainable porosity at 7.9 % is close to the desired value of 10 %. Whilst the topsoil may appear moist it only holds 10.4 % or 18.7 mm soil moisture for rapid plant growth. However, the topsoil has a substantial ‘reservoir’ of tightly held moisture at 19.5 % or 35 mm to support slow growth and survival without irrigation.

Field observation indicated the B21 horizon or upper subsoil to be reasonably well structured and in moderate condition. However, the laboratory analysis indicates it to be denser and more compact than expected. For a clay loam it has a very high bulk density at 1.60 g/ cm³, lacks drainable porosity at only 3.2 % and is likely to have low hydraulic conductivity. In terms of water relations most water is either unavailable at 22.5 mm or tightly held at 18.5 mm with only 8.8 mm being available for rapid plant growth (RAW). The B22 horizon is similar to the B21 horizon, with similar bulk density, similar water holding capacity, but slightly less drainable porosity, and slightly less readily available soil moisture.