Sugarcane and soil acidity - Why should we be worried?

Production systems which promote soil acidification are unsustainable in terms of the maintenance of the soil resource. Potential mechanisms of acidification are discussed with respect to proton generating reactions and evidence is presented to show that a gradual acidification of soils has occurred on a long term basis under sugar cane production systems. This decline in pH has been accompanied by a reduction in cation exchange capacity (CEC) and an increase in exchange acidity. Methods of remediation of both topsoil and subsoil acidity are discussed in brief. It is suggested that in order to avoid the progressive downward movement of protons due to topsoil acidification, soil pH should be maintained above 5.6. In addition, a potential cost effective method of ameliorating subsoil acidity is proposed which is based on the production of Ca(N03)z in the topsoil, its subsequent leaching into the subsoil and the preferential uptake of N03 - by sugarcane roots.