The efficiency of surface application of lime under a no-tillage system is doubtful, particularly with regard to subsoil acidity and to methods of lime requirement determination. A field experiment was carried out on a dystrophic Dark Red Latosol (Haplortox) from Ponta Grossa, Paraná, Brazil, from 1993 to 1998, to evaluate the extent of downward movement of lime applied on the surface under a no-tillage system, and the effect on crop rotation grain yields. A randomized complete block design was used, with three replications. The treatments consisted of dolomitic limestone, at the rates of 0, 2, 4 and 6 t ha-1, calculated to raise the soil base saturation in the 0-20 cm layer, to 50, 70 and 90%. The lime was applied in July 1993. Soybean (1993/94), corn (1994/95), soybean (1995/96), wheat (1996), soybean (1996/97), triticale (1997) and soybean (1997/98) were cultivated, in this sequence. Liming decreased H + Al concentration and increased pH, exchangeable Ca + Mg and soil base saturation up to 60 cm depth. The maximum yield (MTY) and the maximum economic yield (MEY) were obtained, at the 3.8 and 3.3 t ha-1 of limestone. The lime rate to attain MEY was that estimated by the soil base saturation method at 65%, in the 0-20 cm layer, showing this to be an appropriate method for liming recommendation on the surface under a no-tillage system. However, surface application of lime should only be recommended for soil with pH (CaCl2) lower than 5.6 or base saturation inferior to 65%, in the 0-5 cm layer.
Soil acidity; dolomitic lime; lime requirement; base saturation; no-tillage system