Effect of long term soil fertilizer application on forms and distribution of potassium in soil under rice-cowpea cropping system

Abstract

An experiment was conducted at Zonal Agricultural Research Station, VC farm, Mandya to\rassess the effect of long term soil fertility management on behaviour of potassium with\rrespect to different forms and distribution pattern in rice-cowpea cropping system. Soil of the\rstudy area belong to sandy loam texture having initial pH (6.28), EC (0.14 dSm-1), CEC (9.60\rcmol (p+) kg-1), MWHC (20.70%) and bulk density (1.67 g cc-1). The organic carbon (0.34 %),\ravailable nitrogen (163 kg ha-1), available potassium (134 kg ha-1) were low and medium in\ravailable phosphorus (29.20 kg ha-1). Results indicated that the water soluble K content of\rsoils varied from 8 to 16 mg K kg-1 in the surface layer and 5 to 14 mg K kg-1 in the sub surface\rlayer in the plots treated with different fertilizer, manure and their combinations. Exchangeable\rK also ranged between 59 and 116 mg K kg-1 in the surface layer and 58 to 98 mg K kg-1 in the\rsub surface layer. The non-exchangeable K content ranged from 111 to 874mg K kg-1 and from\r160 to 880 mg K kg-1, respectively in the upper and the lower layers. The total K content variedfrom 792 to 3017 mg K kg-1 at 0-15 cm depth and from 874 to 3318 mg K kg-1 at 15-30 cm depth.