Buffer capacity as a method to estimate liming dose in acid soils

Abstract

Objective: It is proposed to use the dolomite buffer capacity (BC_Dolomite) as a method of estimating the lime requirement, in soils that agronomically require a pH increase.

Design/methodology/approach: In six soil samples, with different levels of response to the application of dolomite, the organic matter (OM), the content of sand, silt and clay, pH, K, Ca, Mg and potential acidity (Al+H) were determined. Assuming an apparent density of 1000 kg/m³ and a volume per hectare of 2000 m³, the soils were placed in polyethylene containers and treated with dolomite in doses equivalent to 0, 750, 1500, 2250 and 3000 kg/ha, establishing the BC_Dolomite as the inverse of the slope resulting from the relationship between the pH and the dose of dolomite.

Results: In soils with a low response to the dolomite, the clay and OM content was 280 and 26 g/kg, respectively, and in high response soils, the clay and OM content was 240 and 47 g/kg, respectively. In all cases, in the relationship between pH and dose of dolomite, a simple and direct linear relationship was observed (R² > 0.85; p < 0.05).

Limitations on study/implications: The results obtained under controlled conditions show that BC_Dolomite constitutes a viable method to estimate the lime requirement, since,

Findings/conclusions: the BC_Dolomite showed sensitivity to the complexity of the clay fraction and to the organic matter of the soil, for which the dolomite requirement is equal to the product between the desired pH increase and the BC_Dolomite.