Studies of the interaction of nutrients and toxic substances in soils of different acidity levels have shown that liming will raise the pH, increase the calcium supply and lower toxic levels of manganese and aluminum to tolerable amounts. When the pH of soil reaches 5.5, water soluble manganese is increased as compared with more alkaline soils. As the pH approaches 5.0, aluminum toxicity enters the picture. The amount of lime added should be regulated since an excess can induce deficiencies of iron, magnesium and other nutrients.