Abstract
In an elimination study on an acidified reddish brown sandy loam Oxisol the level of Ca was found to be inadequate for normal plant growth. Relative to Ca uptake, the uptakes of Fe, Mn and Al were high and associated with poor growth. Furthermore the level of N was extremely low, owing to continuous N oxidation and leaching during acidification. This resulted in poor growth and a high uptake of heavy metals relative to Ca, as found with Ca deficiencies. Nitrate-uptake may become so limited under these conditions that the uptake of Ca can be detrimentally affected. Although the availability of Mo declined with increasing acidification, it is clear thatMo is not limiting as regards NO3-reduction and that it must have some other function(s). It appears that Mo is involved in the uptake of NO3 which has an important bearing on the Ca nutrition of the plant and on its ability to grow under otherwise unfavourable conditions.
