Corn yield as affected by liming and tillage system on an acid Brazilian oxisol

Tillage system affects many soil parameters that may influence plant growth. This study evaluated the effect of timing on corn (Zea mays L.) yield and chemical characteristics of a Humic Hapludox (clayey, kaolinitic, goethitic, termic) under both conventional tillage (CT) and no-tillage (NT) systems. Rates of dolomitic lime, from 0 to 18 t ha(-1), were plowed into the soil in 1992 in southern Brazil; our study was conducted from 1996 through 1999. Lime rate was allocated to subplots, and tillage systems to main plots, in a split-plot design. Corn yield increased with liming in all years and was higher with CT than with NT in 2 of 3 yr. Averaged across years and systems, liming increased yield by 66%, which ranged from 4.4 to 7.8 t ha(-1). The highest average yield (7.8 t ha(-1)) was obtained at pH 6.5; yields at pH 6.0 or 5.5 were 97 and 89% of the maximum, respectively. Liming reduced soil organic matter (SOM) in both systems, but nutrients (P, K, Ca, Mg, Fe, Cu, Zn, and Mn) remained above sufficiency on all treatments. Aluminum, pH, SOM, and other nutritional parameters did not differ between tillage systems, partly because limestone was initially incorporated in all plots and partly due to dilution effects in the plow layer because sampling was not stratified in small depths. Some soil restriction impaired by absence of plowing, probably increases in bulk density, offset the benefits of NT on plant growth and was responsible for the smaller yield in this tillage system compared with CT.