Effect of parent material, natural available soil boron, and applied boron and lime on the growth and chemical composition of lucerne on some acidic soils of the Central Tablelands of New South Wales

Abstract

Fifteen acidic soils (0-1 5 cm), three from each of the five main parent materials in the Central Tablelands of New South Wales, were collected for a glasshouse experiment. The hot water soluble boron content of these soils and some other related soil properties were measured. Boron at nil and 1.5 ¦g/g air-dried soil and lime at nil and 670 ¦g/g air-dried soil in a factorial combination were applied to the soils. The effects of the treatments on the performance of lucerne (Medicago sativa cv. Hunter River) grown on these soils were studied. Boron application tended to increase the production of lucerne dry matter on sandstone, shale and slate, and granitic soils, but not on basaltic or alluvial soils. Also, it increased the boron concentration in the leaves of lucerne grown in all soils and consequently, reduced the calcium to boron ratio. The boron levels that produced 90% of the maximum yield and below which boron deficiency symptoms were manifested by the plants, were 0.34 ¦g/g in air-dried soil and 25 ¦g/g in oven-dried leaves. There was a linear correlation (r = 0.98) between the hot water soluble boron content of the untreated soils and the boron concentration in the leaves. The hot water soluble boron content of the soils derived from sandstone, shale and slate, and granite was much lower than the basaltic or alluvial soils and were nearly equal to or below the determined critical level. Although liming had the tendency to induce the symptoms of boron deficiency, the effect of lime was greater than boron in increasing the yield. The role of lime in eliminating the problems of these acidic soils and hence promoting the yield of lucerne is discussed.