THE EFFECTS OF SALT AND BORON ON GROWTH OF WHEAT

Wheat (Triticum aestivum L. cv. Warigal) was grown in a glasshouse in deep pots (0.125x0.125x1.2m) containing sieved solonized brown soil (calcixerollic xerochrept) comprising 0.2 m sandy loam topsoil above 0.6 m treated calcareous sandy loam subsoil and a base layer of light clay 0.26 m thick. The subsoil was treated with a mixture of salts (0, 13, 39, 75 mmol(c) kg-1) and with boric acid (0, 20, 38 and 73 mg B kg-1) in factorial combination. The soil was initially watered to field capacity and water use was determined by regularly weighing the pots. The soil was allowed to dry gradually during the season, but the weights of the pots were not permitted to fall below that corresponding to 17% of the available water holding capacity of the soil. Tillering, dry weight of shoots and grain, and root length density were determined. Water-use efficiency was calculated with respect to total dry weight and grain production. Salt decreased tiliering, dry matter production, grain yield, root length and water-use efficiency (total dry weight): it increased sodium and decreased boron concentrations in the plants. Boron decreased dry matter production (but not tillering), grain yield, root length and water-use efficiency (total dry weight and grain yield): it increased the concentrations of boron and decreased the concentration of sodium in the plants. At the concentrations of salt and boron used (which cover the range normally encountered in subsoils in much of Upper Eyre Peninsula), boron had more deleterious effects on wheat than did salt. Yield was depressed by salt at concentrations of sodium in the tissue commonly found in field-grown plants.