Behavior and status of potassium in a coastal and on inland soil
1988
Mohamed Hussien Ahmed
The soil samples studied varied in their mineralogical composition and chemical characterisitics including pH, CEC [cation exchange capacity], OM [organic matter], exchangeable K, Na, Ca, and Mg, NaTPB-extractable, total K, while the Q/I parameters of the two surface soils examined also varied. The mineralogical composition of the clay fraction of Lipa soil is randomly stratified mica and smectite while La Paz consists of smectites and vermiculite-chlorite integrade. La Paz soil had higher total K and higher amounts of "fixed" K. The lower exchangeable K content La Paz soil was due to the presence of high levels of Ca, Mg and Na which competed for adsorption site on the colloidal exchange complex. Based on the Q/I parameters of the two surface samples, the coastal soil (La Paz) has poorer K status than the inland soil (Lipa). The results of K leaching studies showed that the effect of K source and rate of application on K leaching varied with the soil and leaching number. The sequence of leachability of various sources of K appeared to be KClK2SO4KH2PO4 in both soils and the highest total K leached was observed in the Lipa soil. There was an increase in concentration of K in the leachate when the rate of application was increased in both soils. Results showed that the Ca and Mg leaching were influenced by source and level of application of K. La Paz soil exhibited greater losses of Mg at high rate due to the loss of interlayer Mg in vermiculite.
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