Water and Cation Movement in an Indonesian Ultisol
- Thomas S Dierolf,
- Lalit M. Arya and
- Russell S. Yost
Lime and fertilizer are required to overcome acidity and soil fertility constraints to crop production in the highly weathered soils of Sitiung, Indonesia. The potential leaching of soil amendments is enhanced by the high annual rainfall of 2750 mm and the low effective cation exchange capacity (ECEC) of these soils. The purpose of this study was to understand the relationship of soil water hydrology to the fate of applied soil amendments. Internal soil water drainage (fieldmeasured) and soil moisture release curves (field- and laboratorymeasured) were determined to characterize the soil hydraulic properties of a clayey, kaolinitic, isohyperthermic Typic Kanhapludult. The results indicated that 6 h after the application of 72.5 mm of water during a ]00-min period, water equivalent to nearly 94% of the applied water drained to depths below 112.5 cm. Macropore volume accounted for 26 to 40% of the 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 in a field experiment that examined the effects of various rates and timing of K fertilization (and blanket applications of Ca and Mg) and stover removal on soil K, Ca, and Mg pools. Results show that amounts equivalent to 1% of the K, 5% of the Ca, and 24% of the Mg that were applied as fertilizer nutrients accumulated in the 30- to 90-cm depth. An average of 33% of the K, 26% of the 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 difficult to chemically ameliorate the subsoil below the 30-cm depth and hypothesize that macropore flow through the soil and a continually wet subsoil are the major factors limiting subsoil cation accumulation.
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