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Título

STRATEGIES FOR SUBSURFACE ACIDITY CORRECTION IN SOIL WITH ROCK FRAGMENTS

Resumo

Agricultural soils require acidity correction to reduce their toxic aluminum (Al) levels. The efficiency of surface application of lime in soil under no-tillage system to correct subsurface acidity is still controversial, especially in soils containing rock fragments. In this way, the objective of this study was to evaluate the subsurface acidity correction by three management strategies in a soil with rock fragments cultivated under no-till. This research was carried out in Ivorá/RS, where three different lime managements were defined in a Humic Dystrudept soil: no-tillage (NT) and scarification (SC - until 25 cm depth) with lime application at surface, and scarification_plowing (SC+PL) with lime incorporated into the upper 0–20 cm soil layer after scarification until 25 cm depth. A stratified soil sampling (every 2 cm in the 0–20 cm layer, every 5 cm in the 20–40 cm layer and 40–50 cm depth) was carried out 18 months after lime application. Soil pH and Al content analysis were performed. We considered soil pH values over 5.5 and Al concentrations below 0.5 cmolc dm-3 (~10% of Al saturation) as optimal for crops development. The optimal soil pH value was reached until 6, 14 and 25 cm depth in NT, SC and SC+PL treatments, respectively. In the same way, the optimal Al concentration was obtained in the upper 10, 14 and 30 cm soil layers, respectively. Indeed, pH values decreased and Al concentrations increased progressively from the 0–2 to the 18–20 cm layers in the NT (6.4 to 5.0, 0.30 to 0.73 cmolc dm-3) and SC (6.1 to 5.0, 0.27 to 1.03 cmolc dm-3) treatments, while in SC+PL they remained relatively constant in the plowed layer (averages: 5.75 for pH and 0.29 cmolc dm-3 for Al). Therefore, surface lime application on this soil with rock fragments was not efficient to correct subsurface acidity, not even when preceded by scarification. So, lime incorporation with plowing should be considered, but other factors also need to be evaluated before taking this decision.

Palavras-chave

Liming, no-tillage, stratified sampling, pH, aluminum

Instituição financiadora

FAPERGS (code 22/2551-0000626-4) and CAPES/PROEX

Agradecimentos

CAPES, UFSM, PPGCS and to my research group (GEFERQS)