For decades, soil acidity has been a major constraint to crop production throughout the world. However, in developed nations, the use of lime to counteract acidity in high-input agriculture over the past 50 to 100 years has led to a marked decrease in the area of acid soils under cultivation and to spectacular increases in yields. Still, in the case of deep naturally acid profiles, little amelioration of subsoil acidity has occurred, and in some cases (e.g., in Australia), neutral to alkaline subsoils have actually been acidified as a result of the failure to correct topsoil acidity [1]. In contrast, in developing nations with largely low-input agriculture and farmers able to afford only minimal applications of lime, very little amelioration of soil acidity has taken place. In fact, the condition has probably worsened in many areas.