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The rate and amount of Al3+ released from re-solubilization of the Al-containing polymers and minerals due to the increase in proton activity in the soil solution in subtropical regions is scarce in the literature. The objective of the present study was to track the Al3+ reappearance following its neutralization during the switch from a conventional tillage system to a no-till (NT) system. For this purpose, we evaluated a long-term lime experiment under NT on a subtropical Ultisol. The treatments included varying lime rates, with different historic of lime reapplication. Soil samples were taken at the 0–5, 5–10, and 10–15 cm depth in 1988, 1994, 1995, 1996, 2001, 2003, 2006, 2012, and 2022. The re-solubilization of Al-containing soil polymers and minerals in the 0–15 cm soil layer proceeds slowly in the first 10 years; afterwards, the rate and amount of Al3+ released increased. However, regardless of the lime treatment, the soil never returns its natural acidic state, even after 34 years of the first liming operation. A decrease in the intensity of reappearance of exchangeable Al3+ in the soil profile is clearly observed, compared to the treatment without reapplication of surface lime. We have observed that it takes 7–9 years for 10% of the effective cation exchange capacity to be occupied by Al3+ if limestone is not reapplied on the soil surface; if underdoses are reapplied this level can be maintained for 13–15 years. Furthermore, if larger and more frequent lime doses are used, a low Al3+ saturation (<10%) can be maintained permanently. These findings emphasize the importance of an appropriate liming process at the start of NT, followed with surface limestone reapplication, to ensure a very low Al3+ saturation over a long period of time in the 0–15 cm soil layer. • Al re-solubilization in the 0–15 cm layer proceeds slowly in the first 10 years. • After that, the Al3+ released accelerates the acidification in a chain reaction. • Even 34 years after the first liming, the soil never recovered its natural acidity. • It takes 7–9 years to reach 10% of Al saturation when surface liming is not performed. • Findings reinforce the mandatory of an adequate liming process at the beginning of NT. [ABSTRACT FROM AUTHOR]

Abstract Eucalyptus trees grow in a variety of environmental conditions and cause contrasting effects on soils. Changes in soil geochemistry and mineralogy due to eucalyptus have not been clearly established to date. The objective of this study was to identify evidences of the effects of eucalyptus root system on geochemistry and clay mineralogy of a Ferralsol. Soil samples were collected in different positions of an old eucalyptus site (R1: rhizosphere of small roots; R2: coarse roots, and R3: bulk soil). The soil pH was very acid (3.8) and Al3+ (4.7 cmol c kg−1) and H+ + Al3+ (40.2 cmol c kg−1) were higher in R1 compared to R3. Additionally, reduction of clay fraction content and an increase in the proportion of Al-interlayered clay minerals were also observed in the eucalyptus rhizosphere. This suggests the occlusion of Al3+ in the interlayer space of 2:1 clay minerals and explains the tendency of a low cation exchange capacity of the clay fraction. Then, the acidification due to eucalyptus did not alter the composition of the mineral assemblage (mineral species) but the trend was a decrease of the proportion of the fine clay fraction (<0.1 μm) as well as an increase of the proportion of 2:1 Al-interlayered clay mineral in the clay fraction. The results suggest that when alien tree species are introduced into natural lands worldwide, a comprehensive geochemical-mineralogical approach must be applied in order to provide the extension of constituent changes. Highlights • Soil samples from eucalyptus rhizosphere were compared in their geochemical and mineralogical aspects with bulk soil. • The low soil pH condition in the rhizosphere of eucalyptus resulted in soil acidification and clay dissolution. • Clay dissolution increased Al3+ contents, increasing the formation of hydroxy-Al interlayered clays. [ABSTRACT FROM AUTHOR]

The quality of lime is generally estimated by traditional methodologies, which consist of coarse granulometry and chemical reactivity determinations. Performing a detailed chemical/mineralogical and fine granulometric characterization is the objective of this study. Fifteen lime samples, from an original 52 commercial samples, were analyzed by their granulometric profile (GP) and chemical-mineralogical compositions to discuss limestone quality inside the tree group of traditional efficiency neutralizing power (ENP) and Mg contents. The lime reactivity was estimated using laser diffraction under water and acid solution (1 mol L−1 HCl). The grain-size distribution ranged from 0.563 to 1124 µm and the GP was associated with the chemical and mineralogical compositions. Samples with high ENP (>99%) presented differences in GP regarding Mg contents. Lime with low ENP presents the most varied mineral assemblage, while calcite and dolomite were the predominant minerals in high-ENP samples. Samples containing high Mg were the most sensitive to the acid solution, suggesting great reactivity. This work contributes to a better understanding of limestone quality than routine analyses performed so far. Additionally, the use of the laser diffraction method promotes a rapid lime reactivity test for liming purposes. [ABSTRACT FROM AUTHOR]

Reducing pesticide application in agricultural land is a major challenge for the twenty-first century. Responses of weed seed's germination and seedling's early development to chemical soil conditions around the seed may be a promising way to aid weed control in a no-till system. Thus, the objective of this work was to test, under controlled conditions, whether different chemical conditions affect the germination and development of horseweed [Conyza canadensis (L.) Cronquist]. We used, as treatment, solutions containing different nutrients (P, K, Ca, and Mg), separately and in combination, and at two pH levels (4.8 and 6.5). Phosphorus alone inhibited horseweed seed germination at ~ 7 times while had ~ 4 times reduction in final germination percentage and germination speed index for both pH tested. Other nutrients tested had a no-effect in germination speed index compared to the control treatment. Potassium alone or associated with other ions (P, Ca, and Mg) at pH 4.8 had a synergistic effect on seedling development (root and shoot length). In the same way, K associated with Mg was synergistic to the root length at pH 6.5. Seeds in the control treatment (distilled water) presented a high germination speed index at pH 6.5, while at low pH this parameter was higher when in association with KMg, PMg and Ca. The findings demonstrate that seed germination traits and seedling development of horseweed depend on nutrient kind exposure and pH conditions in the seed environment. This work suggests that adequate topsoil management (i.e., pH and nutrient availability) may aid to reduce weed germination, because, it consists of an important factor of weed occurrence in agricultural areas. [ABSTRACT FROM AUTHOR]

Viticulture plays an important role in generating income for small farms globally. Historically, vineyards use large quantities of phytosanitary products, such as Bordeaux mixture [Ca(OH) 2 + CuSO 4 ], to control plant diseases. These products result in the accumulation of copper (Cu) in the soil and increases the risk of transfer to water bodies. Thus, it is important to evaluate whether the presence of Cu-bearing particles in water is toxic to aquatic fauna. This study conducted chemical, mineralogical, and particle size evaluations on water samples and sediments collected from a watershed predominantly cultivated with old vineyards. The proportion of Cu-rich nanoparticles (<10 nm) in the sediment was ~27%. We exposed zebrafish to different dilutions of water and sediment samples that collected directly from the study site (downstream river) under laboratory conditions. Then, we evaluated their exploratory behavior and the stress-related endocrine parameter, whole-body cortisol. We also carried out two experiments in which zebrafish were exposed to Cu. First, we determined the median lethal concentration (LC 50–96 h) of Cu and then assessed whether Cu exposure results in effects similar to those associated with exposure to the water and sediment samples collected from the study site. The water and sediment samples directly impacted the exploratory behavior of zebrafish, showing clear anxiety-like behavioral phenotype and stress in terms of cortisol increase (during the second rain event). The Cu exposure did not mimic the same behavioral changes triggered by the water and sediment samples, although it had caused similar stress in the fish. Our results highlight that even at low concentrations, the water and sediment samples from vineyard watershed runoff were able to induce behavioral and endocrine changes that may harm the ecological balance of an aquatic environment. Unlabelled Image • Vineyards receive copper-based fungicide known as Bordeaux mixture. • High Cu contents were observed in the sediments of the downstream vineyard area. • Fish exposed to this water + sediments increased their cortisol levels and were anxious. • Behavior and endocrine changes caused by the Bordeaux mixture could harm the ecological balance. [ABSTRACT FROM AUTHOR]