The influence of texture, structure and clay mineralogy on the soil moisture characteristic

Abstract

The relative importance of texture, structure, organic matter and clay mineralogy to the nature of the soil moisture characteristic is examined for an extensive group of Australian soils using numerical classification and diagnostic methods.The presence of pedality, particle size composition and grade of structure were the soil properties most consistently associated with differences between the groups of soils with similar moisture characteristics. By association, field texture was shown to be a useful property. Although the presence of pedality and grade of structure were important, the shape and size of ped had only weak associations with differences in the soil moisture retention.Montmorillonite, iron oxide, vermiculite and quartz were the minerals in the clay size fraction which appeared to be important if they were present. In contrast, the presence of illite did not show any strong associations with a particular position or form of the moisture characteristic.The soil moisture characteristic was successfully modelled as a power function. It appears that being able to group and classify the soil moisture characteristic and then to provide a description of these groups both in terms of soil properties and model parameters is a valuable means of developing simple predictive models for field soils. The error of our predictions for 44 horizons based on this simple approach appears to be only marginally larger than that encountered in conventional laboratory methods, and in view of soil heterogeneity it is argued that following further development these predictions may be adequate in many hydrological and agricultural applications.

Comparison of irrigation scheduling strategies for achieving water use efficiency in highbush blueberry

“…In the present study, midday leaf water potential never fell below (0.66 MPa and mid-morning stomatal conductance consistently moderated between the lowest measurement of 260 mmol m (2 s (1 and the highest of 396 mmol m (2 s (1 and no significant differences were observed between treatments for leaf water potential or stomatal conductance. The apparent absence of a physiological response to the water deficit may be explained by the possibility that actual RAW was greater than that estimated using the model of Williams et al (1983). It is also possible that plants were accessing water deeper than the estimated 40 cm effective rooting depth.…”

“…Soil bulk density measured from 36 soil cores taken from within soil mounds averaged 1.0 g cm (3 (between 10 cm and 40 cm depth) and 1.1 g cm (3 under soil mounds (between 40 cm and 100 cm depth). Applying the soil moisture characteristic model of Williams et al (1983); soil group 7), the theoretical drained upper limit was estimated at 0. (Marsh & Rixon 1991;Batten et al 1994;Bell et al 2005).…”

Evaluation of the SMOS-Derived Soil Water Deficit Index as Agricultural Drought Index in Northeast of Brazil

“…It is well known that the amount of clay and sand has an important influence on the soil water dynamic [22]. In fact, soil water retention is strongly correlated to the clay content [78]. In this context, one could suppose that clay soils may show positive values of SWDIS, in spite of the presence of severe drought conditions (i.e., AWD << 0), leading to values of correlation near to zero or negative when the AWD and SWDIS are compared.…”

Subsoil constraints in Vertosols: crop water use, nutrient concentration, and grain yields of bread wheat, durum wheat, barley, chickpea, and canola

“…8), which shows the robustness of the model in determining CLL on Vertosols with these subsoil constraints. There may be significant differences in other soils due to texture, structure, and clay mineralogy (Williams et al 1983), nutrient deficiency (Ritchie 1981), and the positive and negative influence of various soil biota.…”