WATER AND CATION MOVEMENT IN AN INDONESIAN ULTISOL

Lime and fertilizer are required to overcome acidify and soil fertilit y constraints to crop production in the highly weathered soils of Siti ung, Indonesia, The potential leaching of soil amendments is enhanced by the high annual rainfall of 2750 mm and the low effective cation ex change capacity (ECEC) of these soils, The purpose of this study was t o understand the relationship of son water hydrology to the fate of ap plied soil amendments, Internal soil water drainage (field-measured) a nd soil moisture release curves (field- and laboratory-measured) were determined to characterize the son hydraulic properties of a clayey, k aolinitic, isohyperthermic Typic Kanhapludult. The results indicated t hat 6 h after the application of 72.5 mm of wafer during a 100-min per iod, water equivalent to nearly 94% of the the applied water drained t o depths below 112.5 cm. Macropore volume accounted for 26 to 40% of t he total porosity of the top 22.5 cm of soil and 5 to 7% in the 22.5- to 112.5-cm depth, Cation movement was measured during a 2-yr period i n a field experiment that examined the effects of various rates and ti ming of K fertilization (and blanket applications of Cat and Mg) and s tover removal on soil K, Ca, and Rig pools, Results show that amounts equivalent to 1% of the K, 5% of tile Ca, and 24% of the Rig that were applied as fertilizer nutrients accumulated in the 30- to 90-cm depth . An average of 33% of the K, 26% of bite Ca, and 8% of the Mg applied as fertilizers were not accounted for in the soil or by crop biomass and probably leached below the 90-cm depth, We conclude that is diffic ult to chemically ameliorate the subsoil below the 30-cm depth and hyp othesize that macropore Bow-through the soil and a continually wet sub soil are the major factors limiting subsoil cation accumulation.