Abstract

                                Sixty representative surface soil samples (0-15 cm) were collected from 5 major cropping systems (viz. rice-rice, fallow-bengalgram, groundnut-groundnut maize-maize, rice-maize/mustard) covering 13 mandals in Kurnool district of Andhra Pradesh and among them 30 samples were selected for investigation based on K status. The potassium releasing characteristics of thirty soils and their relationship with plant uptake was studied. The potassium release characters were the highest in maize-maize cropping system and the lowest in groundnut - groundnut cropping system. Lower amounts of cumulative K was observed in all soils except in soils of Srinagaram and Rythunagaram under present investigation. Lower cumulative K and continuous cropping would lead to depletion of soil K reserves and result in K deficiency. All investigated soils recorded less constant rate K than critical value indicating that these soils had low supplying powers to plants. Among the K release i.e cum- K and step K obtained with boiling 1N HNO3 showed maximum positive and significant correlation with dry matter, K content and K uptake while constant K showed minimum correlation.

Key words : Step-K, Constant-K, Cumulative-K, Dry matter, K content and uptake.