Results: Native Release of Potassium (untreated soils)
Parameter
Coef. of det.
r
Illite content
0.71*
Vermicullite content
0.95**
Non exchangeable K content
0.82**
Exchangeable K content
0.88**
Cumulative native K release ranged between 21 mg K kg-1 in Nedumangad
and 103 mg K kg-1 in Dodabhavi
The release of native K is highly correlated with the amount of illite and
vermicullite and the non-exchangeable and exchangeable K content
The highest release was observed in Dodabhavi, containing the highest amount
of illite and vermiculite and the highest non-exchangeable and exchangeable
K content
Nedumangad, Tyamagondalu and Vijaypura released very low amounts of K although
they contain 20% illite. These 3 soils contain also 15-20% of amorphous material
which occur as coatings around silicate minerals and may hinder the release
of K from these soils
