Phosphate-solubilizing bacteria (PSB) transform precipitated inorganic phosphorus into soluble orthophosphates. This study evaluated the efficiency of tricalcium and iron phosphate solubilization in Pikovskaya medium using five bacterial strains (A1, A2, A3, A5, and A6) cultured in acidic and alkaline pH levels. The bacterial strain that proved to be more efficient for P solubilization and was tolerant to pH variations was selected for assessing bacterial growth and P solubilization with glucose and sucrose in the culture medium. The bacterial strains were identified through 16S rRNA gene sequencing as Pseudomonas libanensis A1, Pseudomonas libanensis (A2), Bacillus pumilus (A3), Pseudomonas libanensis (A5), and Bacillus siamensis (A6). These five bacterial strains grew, tolerated pH changes, and solubilized inorganic phosphorus. The bacterial strain A3 solubilized FePO₄ (4 mg L⁻¹) and Ca₃(PO₄)₂ (50 mg L⁻¹). P solubilization was assayed with glucose and sucrose as carbon sources for A3 (Bacillus pumilus MN100586). After four culture days, Ca₃(PO₄)₂ was solubilized, reaching 246 mg L⁻¹ with sucrose in culture media. Using glucose as a carbon source, FePO₄ was solubilized and reached 282 mg L⁻¹ in six culture days. Our findings were: Pseudomonas libanensis, and Bacillus siamensis, as new bacteria, can be reported as P solubilizers with tolerance to acidic or alkaline pH levels. The bacterial strain B. pumilus grew using two sources of inorganic phosphorus and carbon, and it tolerated pH changes. For that reason, it is an ideal candidate for inorganic phosphorus solubilization and future production as a biofertilizer.

Erosion significantly decreases the depth of a soil, the nutrients available for plants, the organic matter and, consequently, the productivity of the edaphic environment. Due to the above considerations, the objective of this study was to evaluate, through various properties, the quality of two eroded soils, one eroded by water and the other by mining activity, amended with biosolids. The quality for both soils was estimated through the selection of a minimum set of data by means of principal component analysis (PCA) and the subsequent realization of correlations, multiple regressions and finally calculations of normalized values (Vn) of those properties considered as indicators of soil quality. According to the results, inorganic nitrogen (NI) and respiratory activity (RA) were the properties selected as indicators to assess quality. For soil eroded by water and by mining activity, NI presented a low and very low quality, respectively (class 4 and 5 of quality according to the calculation of Vn). The quality of RA in soil eroded by mining extraction was very high (quality class 1 according to Vn), and thus it can be considered an ideal indicator for the evaluation of soil quality due to its sensitivity to anthropogenic changes (mining) in soil.

We investigated changes in biochemical activity of a soil cultivated with Ocimum basilicum L. plants and in the oxidative stress of plants caused by the addition of biosolids and inorganic fertilizer. A greenhouse experiment was set up; it consisted of pots containing basil plants to which different treatments with biosolids and fertilizers were added. After 10 and 210 days of the incorporation of the treatments, both the biochemical properties and oxidative stress of the plants were evaluated. Mineralization of nitrogen (N) and respiratory activity increased with a higher dose of biosolid after 10 days of application. After 210 days, there were no changes in the mineralization of N and respiratory activity, catalase showed an increase, while microbial biomass carbon decreased. In relation to the oxidative stress, there was a decrease in the anthocyanin antioxidant capacity, and 2,2-diphenyl-1-picrylhydrazyl (DPPH), total flavonoids, and phenolic compounds were observed in soils treated with biosolids. The results indicated that the biochemical properties of the soil were favored in the presence of biosolids because they increased, especially after 10 days of application. The antioxidant capacity decreased in the presence of biosolids, which suggests that the amendment does not affect such capacity, and therefore oxidative stress could be reduced.

La aplicación de agroquímicos en la floricultura, disminuye gradualmente la fertilidad y poblaciones de microorganismos benéf icos del suelo, siendo los actinomicetos indicadores biológicos de la calidad edáf ica. En el presente artículo se propuso como objetivo comparar los cambios en la densidad poblacional de actinomicetos en suelos florícolas de rosa, clavel y agapando, y su tratamiento con vermicomposta. Los tratamientos fueron agapando como control, suelo con plaguicida del cultivo de rosa, suelo con plaguicida del cultivo de clavel, suelo con plaguicida del cultivo de rosa adicionado con vermicomposta a 40 Mg ha-1 y suelo con plaguicida del cultivo de clavel adicionado con vermicomposta a 40 Mg ha-1. Durante 28 días, se cuantif icó la densidad de población de actinomicetos totales, por el método de conteo en placa. Los suelos florícolas son de textura franco-arenosa, por su bajo contenido en materia orgánica, se adicionó vermicomposta a los tratamientos. La población de actinomicetos totales de los suelos florícolas y vermicomposta fue del orden de 1 × 105 UFC g-1 de suelo, lo que indicó un bajo contenido. Se detectaron cambios en la densidad poblacional de actinomicetos en los tratamientos de suelos florícolas de rosa y clavel con y sin vermicomposta, siendo mayor en los suelos florícolas de rosa y clavel sin la adición de vermicomposta. Los cambios en la población de actinomicetos de los suelos cultivados con rosa y clavel indican que estos microorganismos están adaptados a la aplicación de plaguicidas. La adición de vermicomposta mejoró las propiedades f isicoquímicas de los suelos florícolas en sus respectivos tratamientos.

Vermicompost is considered an environmental quality to manage agricultural residues because it improves the structure, provides nutrients to the soil, and helps to mitigate the impact on the environment. The objective of this study was to know the residence time by applying a kinetic model of carbon mineralization, evaluating chemical and biological parameters obtained during the processing time of a vermicompost. Earthworms (Eisenia fetida) were used comparing different doses of residual sludge (LR) at 0, 10, 20 and 40 Mg, keeping constant the dose of domestic waste (RD) and cattle manure (EV) at a ratio of 1:1 (dry basis). An AxB factorial design was used, where A represented the LR dose and B the type of residues (RD and EV); thus, eight treatments with nine replicates were compared. The pH, organic matter (MO), total nitrogen, C/N ratio, respiratory activity, C mineralization, and residence time were determined. The results of the treatments indicate a slightly alkaline trend. MO was different among treatments, with higher percentage of MO in EV and LR with 40 Mg of LR (28.92 ± 10.78 %, F (7,88) = 2.63, p ≤ 0.01). The percentage of total N was low, but the treatment containing 40 Mg of LR and RD (1.04 ± 0.62 %, F7,88 = 3.87, p < 0.01) stood out. C/N ratios < 20, indicating stability, were recorded in the treatments with LR and EV. The vermicompost obtained by 40 Mg of LR and EV complied with a minimum residence time (less than 70 days) during its processing, which makes it a highly recommendable option for application in agriculture. Vermicompost is considered an environmental quality to manage agricultural residues because it improves the structure, provides nutrients to the soil, and helps to mitigate the impact on the environment. The objective of this study was to know the residence time by applying a kinetic model of carbon mineralization, evaluating chemical and biological parameters obtained during the processing time of a vermicompost. Earthworms (Eisenia fetida) were used comparing different doses of residual sludge (LR) at 0, 10, 20 and 40 Mg, keeping constant the dose of domestic waste (RD) and cattle manure (EV) at a ratio of 1:1 (dry basis). An AxB factorial design was used, where A represented the LR dose and B the type of residues (RD and EV); thus, eight treatments with nine replicates were compared. The pH, organic matter (MO), total nitrogen, C/N ratio, respiratory activity, C mineralization, and residence time were determined. The results of the treatments indicate a slightly alkaline trend. MO was different among treatments, with higher percentage of MO in EV and LR with 40 Mg of LR (28.92 ± 10.78 %, F (7,88) = 2.63, p ≤ 0.01). The percentage of total N was low, but the treatment containing 40 Mg of LR and RD (1.04 ± 0.62 %, F7,88 = 3.87, p < 0.01) stood out. C/N ratios < 20, indicating stability, were recorded in the treatments with LR and EV. The vermicompost obtained by 40 Mg of LR and EV complied with a minimum residence time (less than 70 days) during its processing, which makes it a highly recommendable option for application in agriculture.

Objective: Evaluar el efecto de la incorporación de Dunaliella salina mezclada con fertilizantes orgánicos en un suelo erosionado hídricamente a través de algunas propiedades químicas, como una alternativa para mitigar los efectos causados por la erosión. Design/methodology/approach: Se tomaron muestras de suelo erosionado, y este fue adicionando con dos dosis de fertilizante equino (C) y bovino (V) mezclado con D. salina, teniendo los tratamientos: C (control 0.2% de D. salina), Va (70,000 kg ha-1 y 0.2% de D. salina), Vb (35,000 kg ha-1 de abono y 0.2% de D. salina), Ca (70,000 kg ha-1 y 0.2% de D. salina), Cb (35,000 kg/ha-1 y 0.2% de D. salina). Después de la aplicación de cada tratamiento, se analizó materia orgánica, conductividad eléctrica, pH y mineralización de N a los 15, 30 y 45 días. Results: Los tratamientos con mayor porcentaje de materia orgánica y conductividad eléctrica en todos los tiempos fueron Ca y Va. En los tratamientos Va y Ca, el pH se mantuvo neutro y con los valores más altos respecto a los demás tratamientos a los 15, 30 y 45 días después su incorporación. Findings/conclusions: El tratamiento Va tuvo el mayor contenido de N desde los 15 días hasta los 45 días. Los resultados sugieren que la aplicación de abono orgánico con D. salina puede compensar los déficits en las propiedades químicas causados por la erosión hídrica.