Abstract
The effects of soil chemical changes on soybean root growth, mineral nutrition and grain yield, as a result of surface application of lime under no-till (NT), are still under discussion. A field trial was carried out on a loamy dystrophic Typic Hapludox at Ponta Grossa, Paraná State, Brazil, using a completely randomized block design with three replicates, in a split-plot experiment. The main plots received four dolomitic lime rates applied on the surface (0, 2, 4, and 6 Mg ha-1) in July 1993. In the subplots, two dolomitic lime rates were reapplied on the surface (0 and 3 Mg ha-1) in June 2000. After nine years, liming increased pH, exchangeable Ca2+ and reduced exchangeable Al3+ as well as soil Al3+ saturation down to a 60 cm depth. Re-liming, after two years, also provided soil acidity amelioration to a 60 cm depth. Soybean total root length per soil surface area (0-60 cm) decreased with the surface lime application under NT. The reduction in soil exchangeable Al3+ with liming did not change Al concentrations in the soybean roots and leaves. Surface-applied dolomitic lime under NT brought an increase in Ca and Mg concentrations and a decrease in the Mn level in both soybean roots and leaves. Soybean grain yield was not influenced by surface liming because of the decreased Al toxicity and because root growth was stimulated by soil acidity stress under NT.
Highlights
Brazilian soils are, on its majority, acidic with Al and Mn toxic levels, low base saturation and low P content (Olmos & Camargo, 1976)
Soil acidity problems are commonly corrected by applying limestone
This study evaluated the effects of amelioration of topsoil and subsoil acidity by surface liming and re-liming in a NT system on root growth, nutrient and Al concentrations in roots and leaves, and grain yield of soybean grown without rainfall limitation
Summary
On its majority, acidic with Al and Mn toxic levels, low base saturation and low P content (Olmos & Camargo, 1976). This study evaluated the effects of amelioration of topsoil and subsoil acidity by surface liming and re-liming in a NT system on root growth, nutrient and Al concentrations in roots and leaves, and grain yield of soybean grown without rainfall limitation. Surface-applied lime rates and re-liming on the surface after nine and two years respectively, increased soil pH and the exchangeable Ca2+ level over the five depths (Figure 1).
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