Amelioration of subsoil acidity

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Abstract
In highly weathered regions, acid, infertile subsoils limit productivity by preventing root proliferation and thereby increasing the likelihood of drought stress. An experiment on a Typic Hapludult involving surface application of gypsum and deep lime incorporation investigated the possibilities of ameliorating such subsoils. Yield responses to both treatments were highly significant and stemmed from reductions in subsoil Al and increases in Ca. Root measurements corroborated the fact that the responses were due to root proliferation in the subsoils and consequent resistance to drought stress. Redistribution of roots in the profile in ameliorated subsoils resulted in P insufficiencies being recorded despite high soil test levels of P probably the result of a relatively smaller root surface in topsoil where P had been placed. These results confirm the feasibility of using gypsum and in particular, phosphogypsum as a subsoil ameliorant.