|Soils, Crops and Fertilizer Use: A Field Manual for Development Workers (Peace Corps, 1986, 338 p.)|
|Chapter 11: Liming soils|
Avoid raising the pH by more than one full unit at a time, and don't raise it much above 6.5. It may only be necessary to raise the pH up to 5.5 to 6.0 for best yields of most crops. Overliming can be worse than not liming at all because:
· Raising the pH above 6.5 increases the likelihood of micronutrient deficiencies (except for molybdenum), especially in the case of iron and manganese.
· Phosphorus availability starts declining above a pH of 6.5, due to the formation of relatively insoluble compounds with calcium and magnesium.