DEPLETION AND BUILD UP OF POTASSIUM IN A VERTISOL UNDER RICE-WHEAT SYSTEM AFTER ONE CROP CYCLE
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Date
2005
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Indira Gandhi Krishi Vishwavidyalaya, Raipur
Abstract
Depletion and build up of potassium in a Vertisol under rice-wheat
system after one crop cycle, was studied at Instructional Farm in the
Department of Soil Science, IGAU, Raipur (C.G.). The objectives of the
experiment were (i) to study the crop response to fertilizer K application in
rice-wheat cropping system, (ii) to study changes in soil K fractions
(iii) monitoring changes in K activity ratio (iv) to monitor potassium balance.
The treatments were five graded levels of fertilizer K application (0, 50, 100,
150 and 200 kg K2O ha-1) in four replication using RBD.
The amount of all fractions was higher in surface layer (0-15 cm),
than that in sub surface layer (15-30 cm). The order of dominance of
different forms of potassium in the soil were non-exchangeable K >
exchangeable K > available K > water soluble K. The overall changes in
different forms of K due to cropping after one crop cycle indicated
decreasing trends in available, exchangeable and non-exchangeable K over
initial but water soluble fraction did not show such trend. The initial value of
total K (water soluble + exchangeable + non-exchangeable K) was 2255 kg
ha-1 that increased after rice to 2290 kg ha-1 then decreased to 2123 kg ha-1
after wheat crop.
No crop response was observed in terms of yield, content and K
uptake of rice and wheat crops. This indicated that K status was sufficient to
meet the K requirement of the crops. The negative K balance after one crop
cycle indicated that crop removal exceeds K application in all the treatments.
Study on changes in K activity ratio revealed that activity ratio
increased upto the application of 150 kg K2O ha-1 at both soil depths,
however, higher K activity ratio was observed at surface layer than that at
subsurface layer.