Navegando por Autor "Sadeghian, Siavosh"

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    Contribution of mycorrhiza and phosphate-solubilizing fungi in coffee seedling growth in four soils with different fertility conditions
    (Instituto Agronômico (IAC), 2025-01-17) González-Osorio, Hernan; Sadeghian, Siavosh; Mira, Beatriz Eugenia
    Phosphorus (P) is a limiting nutrient for coffee seedlings. To meet this requirement, coffee growers usually apply di-ammonium phosphate (DAP), which is highly sensitive to local price fluctuations. The use of arbuscular mycorrhizal fungi (AMF) and phosphate-solubilizing fungi (PSF) has been recommended, but the results derived from their application are inconsistent and uncertain, depending on soil fertility status. The response of AMF and PSF application in the plant growth of coffee seedlings during the nursery stage was evaluated in four non-sterile soils, which represent the most abundant type of soils in the coffee regions of Colombia: Eutropept, Dystropept, Fulvudand, and Ultisol. The treatments included a commercial AMF inoculum, PSF-Phlebia subserialis-CH4, and a consortium of AMF+PSF, at four P levels (0, 0.5, 1, and 2 g.plant-1 P2O5) using DAP fertilizer. Shoot dry weight (SDW) was affected by P applications in Fulvudand. In the other soils, a P-response occurred with 0.5 g.plant-1 , whereas 1 and 2 g.plant-1 of P2O5 caused a significant reduction in SDW. AMF increased SDW by 40% in Eutropept. The negative effect of higher P amounts was mitigated (> 70%) through PSF and AMF+PSF in Ultisol and Eutropept, respectively. In plants in which microorganisms increased SDW, the P concentration was 0.17 to 0.22%. The plant growth promotion of coffee seedlings during the nursery stage with AMF and/or PSF applications varied according to soil type and P amounts applied.
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    Phosphorus fixation and its relationship with soils chemical properties of the coffee zone of Huila, Colombia
    (Universidade Federal de Lavras, 2023-11-01) Poveda, Vanessa Catalina Díaz; Sadeghian, Siavosh
    Adsorption is one of the critical processes in phosphorus (P) availability in plants. In the coffee crop (Coffea arabica), the highest dose of P is supplied in the vegetative phase, so its management is fundamental to guarantee the optimum growth of plants. The aim of this work was to determine the P fixation capacity and its relationship with the soil chemical properties of the Huila coffee zone, Colombian department, with the largest area planted with coffee. The adsorption isotherms were obtained by equilibrating the soil with 30mL of KH2PO4 solution dissolved in a 0.01M CaCl2.2H2O, containing concentrations of P between 50 and 4.200 mg kg-1. The P adsorption was measured for 60 soil samples collected from the five main cartographic units of the department: Campoalegre, El Recreo, La Cristalina, Saladoblanco, and San Simón. The data fitted to the linear and nonlinear Langmuir model forms. It was found that the soils of the region have a variable P fixation capacity, with values of q (adsorption at 0.2 mg L-1 in solution) between 8 and 1330 mg kg-1 and b (maximum adsorption capacity) from 117 to 3916 mg kg-1, without finding an association with the evaluated soil units. A correlation of q and b was found between Al3+, Al3+ saturation, pH, Ca2+ and Mg2+, and base saturation.