Quantity-intensity parameters of potassium in relation to uptake by Guinea-corn in representative soils of the ecological zones of Nigeria
1999
Akinrinde, E.A. | Obigbesan, G.O.
Quantity-intensity (Q-I) relation studies were often used to supplement information obtained from conventional soil tests for the estimation of potassium (K) needs of crops. With a view to ascertaining the reliability of the Q-I relation parameters for comprehensive characterization of K dynamics in typical Nigerian soils, K values derived from Q-I isotherms were related to neutral normal ammonium acetate (1 N NH(4)OAc, pH 7.0) (exchangeable) K, other soil K forms [non-exchangeable (K(ne)), exchange (K(e)), mineral K (K(m)), and solution K (K(s))] and the K uptake by Guinea-corn (Sorghum bicolor, var. LS 187) subjected to weekly cuts in Neubauer cultivation vessels. Most of the soil K (about 98%) was in the form of soil minerals while less than 1% was plant available whereas about 1% was trapped within the interlattice layers of the clay minerals (as fixed K or K(ne)). Mineral K (K(m)) content was closely related to total K(K(t)), but not to the other forms, K(ne), K(e), and K(s). A close relationship was noted between the two components of labile K (K(e) and K(s)). Except for % K saturation, the relationships between the K measurements with plant response were poor. The results of these investigations clearly demonstrate that the Q-I relation could not adequately characterize the K dynamics of these tropical soils.
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