Distribution of forms of potassium in relation to different agroecological regions of North-Eastern India

Distribution of potassium (K) in soils is governed by the agroecological region (AERs), as the operational intensity of factors and processes of soil formation vary with AER. Therefore, we aimed at finding out the relationship between the forms of K(K forms) with AER and the association of K forms with soil properties in the North-Eastern region of India. For this, horizon-wise soil samples were collected from pedons, three each from three AERs (15 (hot sub-humid to humid), 16 (warm per-humid) and 17 (warm per-humid with less cool winter)) in the North-Eastern India. The water balance diagram for AER shows that precipitation (P) exceeds the potential evapo-transpiration (PET) from June to October, AER 16 shows almost no period when the PET is more than the P and AER 17 shows that the region experiences only a short water deficit of 100–150 mm during post-monsoon period. Soil samples were analysed for physical and chemical properties and K forms. The soils were acidic to neutral with low cation exchange capacity (CEC). The water-soluble K ranged between 0.006 and 0.144 cmol kg^?1, exchangeable K between 0.07 and 0.54 cmol kg^?1, fixed K from 16.7 to 61.3 cmol kg^?1 and total K from 17.4 to 63.6 cmol kg^?1 in soils of different horizons. Further, the results revealed that all the K forms followed the trend of AER 16 > AER 17 >AER 15. Exchangeable K showed higher correlation with clay (r = 0.519**), while fixed K with organic carbon (r = 0.390*).