Potassium Dynamics and Response to Applied Potassium in Paddy-Paddy and Sunflower Bengalgram Cropping System Under Vertisols in TBP Command Area
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Date
2011
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UAS Dharwad
Abstract
soil samples of dominant cropping system of TBP command area for
physico-chemical and mineralogical properties of the soils, quality and distribution of
different forms of potassium, potassium reserves in textural fractions and its fixation.
Field experiments were also conducted to study the response of applied potassium in
paddy-paddy and sunflower-bengalgram sequence with farmer’s participation. The
soils are low in water soluble K, medium to high in exchangeable K, which ranged
from 78 to 238 mg kg-1 in surface and from 103 to 265 mg kg-1 in subsurface layers.
The non exchangeable K varied between 342 to 602 mg kg-1 and 374 to 631 mg kg-1 in
surface and subsurface layers, respectively. The amount of lattice K content in surface
horizons varied from 2.90 g kg-1 to 9.88 g kg-1 and 3.25 to 11.0 g kg-1 in subsurface
layers of both the cropping sequence. The total content ranged between 3.38 to 10.56
and 3.89 to 11.0 g kg-1 in surface and subsurface horizons, respectively. The different
forms of K were positively correlated with each other in soils of paddy-paddy
sequence indicating its dynamic equilibrium compared to soils of sunflowerbengalgram
sequence where no dynamic equilibrium exists between different forms
of K. The soils of paddy-paddy sequence had higher K fixation compared to soils of
sunflower-bengalgram sequence. The mineralogy of soils revealed the dominance of
smectite in the clay fraction in both cropping sequence. The paddy, sunflower and
bengalgram crops have responded to potassium application in both kharif and rabi
seasons in a cropping sequence involving paddy-paddy and sunflower-bengalgram.
The potassium balance sheet was negative in soils of both the cropping sequences.