Assessment of potassium status in soils under different land use systems of Assam

The knowledge on contribution of potassium (K) from different pools become pertinent for evaluating soil fertility status and providing better interpretation in near future. The present study aims to assess the soil K pools under major land use systems of Assam, viz. mulberry, sugarcane, tea and rice-mustard under three depths (0-15, 15-30 and 30- 60 cm) and categories them, based on the content of exchangeable K (Exch-K) and non-exchangeable K (NEK). In 0-15 cm soil depth, Exch-K content was highest in the rice-mustard land use system (49.7 mg/kg) whereas, NEK content were highest in the mulberry land use system (1351 mg/kg). Both Exch-K and NEK content were found to be highest under mulberry system at 15-30 and 30-60 cm depth. Mulberry and rice-mustard land use systems had higher amounts of NEK but lower in available K, thereby, need maintenance dose of K. The NEK pools were included along with Exch-K in categorising soils into nine groups for evolving better strategies to manage soil K fertility. Results revealed that most of the soils were in category with low Exch-K and NEK content. Irrespective of depths, soils from nine sites were low in both Exch-K and NEK. The third category soils with low Exch-K and high NEK had the second highest number of soils in all the depths.Thus, soils having low levels of both Exch-K and NEK, the K must be applied immediately to sustain crop productivity under different land use systems.

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