Annual pattern of soil moisture stress under sown and native pastures

Abstract

Soil moisture fluctuations were measured under a phalaris-white clover pasture and under three native pasture types in the New England region of New South Wales over a 4-year period, by means of the gypsum resistance block technique. The results indicate that large differences in available soil moisture occur at times within areas of apparently similar soil type and that these differences are reflected by the different pasture types in the area. Although the lengths of the period during which soil moisture was unavailable differed considerably under the different pastures the general pattern was similar. The months of greatest soil moisture stress were December, January, April, and May, while the period of most favourable soil moisture was from June to November. Thus although most of the rain fell during the period December to May the rain which fell from June to November was more effective in maintaining available soil moisture. The subsoil dried out more rapidly and remained dry for a longer period under the sown pasture than under the native pasture type which the area previously carried, owing to the greater rate of removal of available soil moisture from under the sown pasture. Of the three native pasture types studied, the most favourable soil moisture pattern for plant growth occurred under the Sorghum-Themeda pasture. This pasture type may be a useful indicator of areas with soil conditions favourable for the growth of productive sown pastures.