Potassium quantity intensity parameters of soils under predominantly rainfed mango (Mangifera indica) orchards

摘要

A study was carried out to establish the quantity intensity relationship of potassium (K) in soils under mango orchards. Equilibrium activity ratio of potassium (AR(e)(k)) in mango orchard soils ranged from 1.20 x 10(-3) (S4) to 41.30 x 10(-3) (S9) (mole L-1)(0.5). AR(e)(k) was significantly and positively correlated with available forms of K, K saturation percentage, Labile potassium (K-L) and potassium held on specific sites (K-X) and negatively correlated with free energy of exchange (-Delta G). Nearly 80 per cent of the mango growing soils recorded PBC0K (potential buffering capacity of potassium) values of < 75 cmol (+) kg(-1)/(moles L-1)(0.5) with least being 5.1 cmol (+) kg (-1)/(moles L-1)(0.5). The PBC0K was positively and significantly correlated with cation exchange capacity (CEC). The Delta K-0 (K on non-specific sites) values for mango growing soils varied from 0.069 to 0.248 cmol kg(-1) of soil. K-X ranged from 0.019 (S6) to 0.522 (S9) cmol kg(-1) of soil. The Delta K-0, K-L and K-X shared a positive correlation with different forms of K and K saturation percentage. Considering the free energy of exchange concept, majority of the soils were deficient in potassium content. The negative relation of Gapon selectivity coefficient (K-G) with easily available forms of K confirms that increased K selectivity will decrease its presence in solution and easily exchangeable pools. Leaf K was positively and significantly correlated with Delta K-0 and PBC0K, whereas no relation of leaf K was observed with forms of K indicating that QI approach gives a better insight into fruit K requirements.