Author : Sri Djuniwati Wipartono

Summary : The study was conducted to determine the clay mineral composition, potassium status, and exchange characteristics of major agricultural soils in West Java, Indonesia. Potassium availability indices, including HC1-extractable potassium (K), NH4OAc-extractable K, NaTPB extractable K, and Q/I parameter were studied using soils from Padalarang, Cipatat, Cisarua, Sukabumi, and Pelabuhan Ratu, all in West Java. The soils differed in their mineralogical and chemical characteristics. The mineralogical composition of the clay fraction showed that of the five soils contained kaolinite. However, smectite was the dominant constituent of the clay fraction on the soils. Likewise, soil from Cipatat, Cisarua, and Sukabumi appeared to contain undetermined quantities of amorphous mineral. Regarding the c hemical characteristics of the soils, Padalarang had the highest total K, HCL-extractable K, NaTPB extractable K, and highest in Gapon selectivity coefficient (K (subscript G)). For the Q/I parameter, Padalarang also exhibited the highest value of /\ K degree and potential buffering capacity of the soil for K (PBC (superscript K)) although it contained lower value of measure of the degree of availability of K (AR (superscript K) (subscript e)). However, Cipatat, the most weathered of the five soils whose clay particle largely kaolinite exhibited the lowest total K, HCL-extractable K, NH (subscript 4)OAc-extractable K values and the lowest (together with Cisarua). NaPTB-extractable K, likewise, Cipatat had the lowest AR (superscript K) (subscript e), /\ K degree, K (subscript x) and PBC (superscript K) values. These observations were expected because of the colloidal properties of kaolinite. The effect of K applied to the soils generally showed that retension of K from K (subscript 2)SO (subscript 4) was greater than from KCl. Consequently, and it was more obvious in certain soils that K uptake by two-week-old corn was greater in KCl than those in K (subscript 2)SO (subscript 4)-treated samples. The correlation of the various pair, K parameters revealed the following significant correlations: K uptake vs. NH (subscript 4)OAc-extractable K, K uptake vs. K (subscript x), total K vs. HCl-extractable K, total K vs. /\ K degree , total K vs. K (subscript x), total K vs. PBC (superscript K), HCl extractable K vs. NH (subsript 4)OAc-extractable K, HCl-extractable K vs. /\ K degree, HCl-extractable K vs. PBC (superscript K), NH (subscript 4)OAc-extractable K vs. K (superscript x), NaTPB extractable K vs. /\ K degree, NaPTB extractable K vs. PBC (superscript K) and /\ K degree vs. PBC (superscript K).