Soil pH and base saturation are important parameters for evaluating the effects of acidity on plant growth. However, the relationship between soil pH and base saturation (V%) has been poorly studied in Brazil. The aim of this study was to evaluate the influence on the cation exchange capacity (CEC) on this relationship for soils of Mato Grosso do Sul, Brazil, using a database consisting of 30,244 analyses of soils collected from 0–0.2- and 0.2–0.4-m depths. The CEC at pH 7 of analyzed soils varied from 3.4 to 40.5 cmol_c·dm^-3 and were grouped into four classes (< 6, 6–10, 10–20, and > 20 cmol_c·dm^-3) for each soil layer. The V% versus pH relationship was CEC dependent for both soil layers. For 0–0.2 m, V% was directly related to CEC (< 6, 6–10, 10–20, and > 20 cmol_c·dm^-3) and reached 50, 55, 60, and 74% at pH 5 and 66, 73, 81, and 88% at pH 6, respectively. Predicting V% in relation to pH was also affected by CEC, with a decrease in the correlation of p = 0.82 for CEC < 6 cmol_c·dm^-3 to p = 0.64 for CEC > 20 cmol_c·dm^-3. The decrease in this correlation was related to low clay content (17%) of soils with CEC < 6 cmol_c·dm^-3, which provided low buffering capacity. For soils with CEC > 20 cmol_c·dm^-3 and higher clay content (45%), greater buffering capacity was observed associated with kaolinite. Findings suggest that CEC should be considered to understand the relationship between V% and pH CaCl₂.

Needle chlorosis (NC) in Pinus taeda L. systems in Brazil becomes more frequent after second and third harvest rotation cycles. In a study to identify factors contributing to yellowing needle chorosis (YNC), trees were grown in soils originating from contrasting parent materials, and soils and needles (whole, green and chlorotic portions) from 1- and 2-year-old branches and the first and second needle flush release at four sites with YNC on P. taeda were analyzed for various elements and properties. All soils had very low base levels (Ca²⁺, Mg²⁺ and K⁺) and P, suggesting a possible lack of multiple elements. YNC symptoms started at needle tips, then extended toward the needle base with time. First flush needles had longer portions with YNC than second flush needles did. Needles from the lower crown also had more symptoms along their length than those higher in the canopy. Symptoms were similar to those reported for Mg. In chlorotic portions, Mg and Ca concentrations were well below critical values; in particular, Mg levels were only one third of the critical value of 0.3 g kg⁻¹. Collectively, results suggest that Mg deficiency is the primary reason for NC of P. taeda in various parent soils in Brazil.

The aim of this study was to evaluate the differential response to land use changes between native forest and croplands regarding the quantitative soil variables of aggregate weight classes and different carbon pools in extremely kaolinitic soils from the east coast of Brazil. In the soil A horizon, the total (TOC) and dissolved (DOC) organic carbon contents were analyzed. In the 0–0.08 m soil layer, the weight and the organic carbon content (Cag) were determined for six size aggregate classes. The mean differential (Δ) of each property for each area was calculated. Overall, the TOC and DOC were greater in the native forest sites over the counterpart cultivated sites within each area. The ΔDOC of all the five areas were negative. The ΔCag of the 1–2 mm and 0.053–0.105 mm soil aggregate classes of Sooretama were the only ones with mean positive values. The ordination of the five areas by the ΔCag in the six soil aggregate size classes isolated Coruripe as the area with the most negative differentials, because of the forest conservation and management of the cropland. The differentials of organic carbon between forest and agricultural use of the analyzed properties did not reveal a possible effect of soil texture.