Peranan Keragaman Mineralogi Lempung dalam Strategi Pernupukan P pada Tanah-Tanah Mineral Masam.

Acid mineral soils play an important role in agricultural extension in Indonesia. Major distribution of these soils are in Sumatra, Kalimantan, Sulawesi and West Papua. These soils were viewed as a marginal soil since the productivity level is low due to severely deficient in P and micronutrients. The high fixation of P presumably related to high contents of Fe and AI oxides. Soil samples were taken for every 20 cm from surface to give a total of 30 samples e.g. 14 samples from Lampung, 10 samples from West Java, and 6 samples from Central Java. The samples. Soil kaolin was concentrated from the clay fraction by removal of iron oxides in buffered dithionite-citrate-bicarbonate solution. Iron oxides were concentrated by dissolving kaolin with strong alkali solution. Measurements of P sorption by soil, kaolin and iron oxides were conducted by equilibrating 200 mg of air dry soil