Seedling growth on Mulga soils and the ameliorating effects of lime, phosphate fertilizer and surface soil from beneath poplar box trees.

Abstract

Phosphate fertilizer, lime (CaCO3), and soil from beneath poplar box trees (Eucalyptus populnea) were incorporated into the surface of an acid sandy red earth (mulga soil) in pots. The effect of these treatments was studied on the growth rate and yield of seedlings of 7 exotic pasture species, Cenchrus ciliaris cv. Biloela, C. ciliaris Q10087, C. ciliaris Q10077. Schmidtia pappophoroides, Eragrostis curvula CPI 30379, Anthephora pubescens and Stylosanthes fruticosa, plus 3 native species Monachather paradoxa, Digitaria ammophila and Aristida armata. Phosphate fertilizer significantly increased growth rates and yields on all soils of all species except E. curvula, S. fruticosa, M. paradoxa and A. armata. Lime, sufficient to raise the pH from 4.8 to 7.7, only slightly improved plant growth overall, although the effect was significant on the three C. ciliaris lines in the absence of added phosphorus. Box surface soil significantly increased growth rate and size of C. ciliaris, especially the cultivar Biloela, and to a lesser extent that of A. pubescens, M. paradoxa and .T. pappophoroides. This improvement in seedling growth on soil from beneath box trees could be at least matched by the addition of phosphorus to mulga soil. Yet the shoots of seedlings growing in box surface soil appeared deficient in phosphorus, indicating a lower availability to plants of such phosphorus than chemical tests would indicate. Evidence in research literature indicates that the results obtained point to aluminium toxicity as being a major factor limiting seedling growth of C. ciliaris on mulga soils.