Fertility Of Acid Soils
Published 1991 · Chemistry
Soil acidity is represented by a set of factors that affect plant growth, aluminium toxicity being the most important. Lime requirement can be defined as the amount of lime necessary to reduce soil acidity, most commonly to a pH value near neutrality, but in some cases only to neutralize exchangeable aluminium. Since there are wide differences of crop tolerance to soil acidity, these definitions are often not satisfactory. A better alternative is in terms of the specific requirements of crops. In highly weathered soils this means, for many crops, liming to pH values much higher than those reached by neutralizing exchangeable aluminium. Subsoil acidity is normally not considered in liming practices, but it might restrict root growth because of calcium deficiency or aluminium toxicity. Direct neutralization of subsoil acidity is in general, not possible, but improvement of the root environment is possible by leaching salts through the soil profile, to increase calcium content and reduce aluminium activity in the soil solution. The salts can originate from liming of the surface soil or by application of gypsum. As a result of the amelioration of acid subsoils, the uptake of water and nitrate-nitrogen by crops can be enhanced.