Abstract:
Among the essential plant nutrients, potassium (K) is considered as a major nutrient
that affects most of the biochemical and physiological processes in plants. Supplying
naturally available K to plants through a special compost mixture would eradicate
the requirement of chemical fertilizers such as Murate of Potash. This study is
focused on producing a special compost mixture (Super Compost) that contains a
significantly higher amount of potassium in available forms. The study was carried
out according to the Randomized Complete Block design, using farm waste
inoculated with rich natural microbial cultures extracted from virgin soils. The
treatments used are: compost, compost + 10% feldspar, sterilized compost + 10%
feldspar (control), compost + 10% feldspar + microbial culture from Sinharaja soils,
compost + 10% feldspar + microbial culture from Kalthota soils, compost + 10%
feldspar + microbial culture from Sri Pada soils and compost +10% feldspar +
compost tea. To each mixture, feldspar was added at a rate of 10% of the weight of
the compost pile. Available K was analyzed by a flame photometer using the
digestion method. A pot experiment was conducted with nine treatments for the
MICH3 variety of chilli and the BG250 variety of rice to evaluate the effect of
different compost mixtures on plants. It was clearly evident that the potassium
feldspar and natural microbial cultures significantly increased the available K
content in compost (P<0.001). The highest level of available K was detected in the
treatment with the microbial culture from Sinharaja (50g/l) followed by the
treatment with the microbial culture from Kalthota natural forest (5g/l). The
response to the microbial cultures from Sri Pada (50g/l) was late. However a jump
in available K was observed in the 12th week, for this compost with feldspar. Chilli
yield was significantly increased by the compost treated with feldspar (3Kg/30Kg)
and microbial culture from Sinharaja (50g/l). Both panicle formation and tillering
of rice were significantly increased by the same compost. Microbial cultures taken
from Sinharaja (50g/l) and Kalthota (50g/l) natural ecosystems are effective
microbial cultures in solubilizing potassium from feldspar.
