Abstract:
Aluminium toxicity is the major factor limiting
crop production in the acidic soils and the usual
practice of alleviating aluminium toxicity is liming* /
The present investigation was carried out to find out
the distribution of water s dluhle and exchangeable
aluminium in the acidic upland soils of Kerala and
to test the suitability of exchangeable aluminium as
an index for liming them* It was further programmed
to find out the growth, yield and nutrient uptake
pattern of two acid sensitive crops namely cowpea and
fodder maize in soils under different levels of exchangeable
aluminium brought out by the use of different
levels of lime*
Chemical analysis of eighty soil samples
representing the five major upland soil types of Kerala
viz* laterlte, alluvial, red loam, sandy and forest
a oil have indicated the highest amount of exchangeable
aluminium and percentage aluminium saturation in the
laterite soils*
The soil with 3 high level of exchangeable
aluminium and percentage aluminium saturation was
selected for conducting a pot culture experiment to
test the suitability of using exchangeable aluminium
as an index of liming* The exchangeable aluminium
content of this soil was maintained at different levels
by applying different levels of lime and the performance
of these crops in this soil was compared by
making biometric observations and by chemically analysing
plant and soil samples*
From the results of the study it was seen that
higher levels of exchangeable aluminium adversely
affected the growth, yield and nutrient uptake In
cowpea and fodder maize*
Maintenance of exchangeable aluminium at
1*26 me/100 g with a corresponding percentage aluminium
saturation valua of around 30, by the use of 500 kg
lime/ha appeared to be the optimum for maximising the
yield of cowpea* But in fodder maize this level of
lime was found to be insufficient and complete elimination
of aluminium toxicity appeared to be essential
for maximising production*
Since the critical levels of exchangeable
aiuainiua appears to be different for different
crop3, it is desirable that lias levels to reduce
exchangeable aluminium to such a critical level alono
be applied. The results of the present study thus
point to the advantage in adopting the exchangeable
aluminium level of soil as a better index of liming
for various crops grown in the upland acidic soils of
Kerala.
