Potential effect of land-leveling on soil fertility in a Brazilian rice soil

Land-leveling to improve water management in lowland rice (Oryza sativa L.) production is becoming common in many countries. This technique exposes subsoil by removal and deposition of surface soil from high- to low-lying areas. The potential effect of land-leveling on soil fertility was studied in samples from an alluvial soil at depths of 0- to 5-, 5- to 15-, and 15- to 25-cm. Levels of soil cation exchange capacity; dilute acid-fluoride extractable P; DTPA extractable Cu, Mn, and Zn; exchangeable K; hot-water soluble B; and organic matter decreased with soil depth; whereas, soil pH increased with depth. Relatively low amounts of dilute acid-fluoride extractable P, exchangeable K, and DTPA extractable Zn occurred in the 15- to 25-cm layer of the soil. These data indicate the high likelihood that K, P, and Zn deficiencies would occur in rice grown on the subsoil that was exposed by land-leveling.