Surface application of lime for crop grain production under a no-till system

The effectiveness of surface application of lime to soils under a no-till (NT) system, particularly with regard to subsoil acidity, is uncertain, and long-term data is needed to determine optimum surface liming rates in this cropping system. A field experiment was performed in the period from 1993 through 2003 in Parana State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate the extent of the downward movement of surface-applied lime in a NT system, and the effect on grain yields under crop rotation. The treatments consisted of dolomitic limestone at the rates of 0, 2,4, and 6 t ha(-1), calculated to raise the base saturation in the topsoil (0-20 cm) to 50, 70, and 90%. Surface-applied lime under NT was effective in alleviating soil acidity below the point of placement, and increased the cumulative grain yield of the crops. The effects of surface liming on all three acidity-related variables (pH, Al, and basic cations) were significant at 0- to 5- and 5- to 10-cm depths from I yr onward, and also at the 10- to 20-cm depth from 2.5 yr onward, remaining consistent for a period of up to 10 yr after liming. The maximum economic yield was obtained at 4 t ha(-1) of limestone, showing that the lime rate estimated by the soil base saturation method at 70% in the 0- to 20-cm depth was appropriate for surface liming recommendation in a NT system.