Potassium Exchange Isotherms as a Plant Availability Index in Selected Calcareous Soils of Western Azarbaijan Province, Iran

Authors : Abbas SAMADI

Pages : 213-222

View : 12 | Download : 3

Publication Date : 2006-05-01

Article Type : Research Paper

Abstract :Potassium insert ignore into journalissuearticles values(K); exchange isotherms insert ignore into journalissuearticles values(quantity-intensity technique, Q/I); and K values derived from the Q-I relationship provide information about soil K availability. This investigation was conducted to study the relationships among K Q/I parameters, available K extracted by 1 N NH4AOc insert ignore into journalissuearticles values(exchangeable K plus solution K);, potassium saturation percentage insert ignore into journalissuearticles values(K-index, %);, and the properties of 6 different calcareous agricultural soils. In addition, the relationship of tomato plant yield response to the K requirement test based on K exchange isotherms was investigated. The Q/I parameters included readily exchangeable K insert ignore into journalissuearticles values(DK0);, specific K sites insert ignore into journalissuearticles values(KX);, linear potential buffering capacity insert ignore into journalissuearticles values(PBCK);, and energy of exchange of K insert ignore into journalissuearticles values(EK);. The results of X-ray diffraction analysis of the oriented clay fractions indicated that some mixed clay mineral, some chlorite/illite clay minerals, along with palygorskite and kaolinite were present in the soils. The soil solution K activity ratio at equilibrium insert ignore into journalissuearticles values(AR0); ranged from 0.0014 to 0.028 insert ignore into journalissuearticles values(moles l-1);0.5. The readily exchangeable K insert ignore into journalissuearticles values(DK0); was between 0.044 and 2.5 insert ignore into journalissuearticles values(cmolc kg-1 soil);, which represented an average of 51% of the exchangeable K insert ignore into journalissuearticles values(Kex);. There was a significantly positive relationship between DK0 and NH4AOc-extractable K insert ignore into journalissuearticles values(r = 98, P < 0.001);. The soils showed high capacities to maintain the potential of K against depletion, as they represented very high linear potential buffering capacities insert ignore into journalissuearticles values(PBCK); [44-177 cmol kg-1/insert ignore into journalissuearticles values(mol l-1);0.5. The EK values for the check treatments ranged from -2736 to -4117 calories M-1, and, for the treatments in which 120 mg K l-1 was added, varied between -2193 and -2657 calories M-1. The percentage of K saturation insert ignore into journalissuearticles values(K-index, %); ranged from 3.8% to 10.2%. Analysis of variance of the dry matter insert ignore into journalissuearticles values(DM);, K concentrations, and K uptake of tomato plants indicated that there were no significant differences insert ignore into journalissuearticles values(P < 0.05); among the adjusted levels of K as determined by the exchange-isotherm curve.
Keywords : Readily exchangeable K, specific K sites, buffering capacity, energy of exchange, K index, availability