Marina Sánchez de Prager

Solubilization of iron and calcium phosphates by soil fungi isolated from coffee plantations

Almost 900 fungal isolates were obtained from eight coffee plantations in Colombia and Mexico. Of these, 76 isolates showed activity to solubilize Ca3(PO4)2 (PCa) and FePO4·H2O (PFe), which had been added to agar in a plate test. Generally, PCa was better solubilized than PFe. Colombian isolates were generally somewhat less effective than Mexican isolates. The two most effective isolates from each country with apparent highest PFe, solubilization potential were selected and cultivated in liquid medium containing PFe, which is more prevalent in tropical soils. The pH value, solubilized P in the medium and P uptake in fungal biomass were determined. After 24 days, Cylindrocarpon didymum and C. obtusisporum (both from Colombia) had solubilized 9.9 and 6.4 mg PO4 3--P L−1 and took up 8.6 and 11.6 mg P in biomass. Penicillium janthinellum and Paecilomyces marquandii (both from Mexico) solubilized 7.0 and 1.9 mg PO4 3--P L−1 and took up 11.3 and 17.3 mg P in biomass. The potential practical use of the four fungal isolates for different strategies in making more P available for coffee growth is discussed.

Dinámica de los hongos de Micorriza Arbuscular (MA) en un Humic Dystrudepts sembrado con maíz Zea mays L. y Abonos Verdes (AV)

Green Compost (GC) have a positive impact on physical, chemical and biological properties of the soil, among them, the expression of the MA. In a Humic Dystrudepts in a mountainous area of Palmira (Valle) five treatments were established: (T), fertilization of insdustrial chemical synthesis (FQ), green manure (AV), Compost (C) and green manure compost (AVC), in a settlement of randomized complete blocks with three replications. As GC intermingled Canavalia ensiformis L. and Axonopus scoparius F., were harvested in prefloration of the legume, incorporated and became the first planting of corn, variety ICA V-354, monitored during 150 days, until time of fill of cob, when assessed length total external mycelium, LMET (Technical of the membrane filter method and the intercepted of Miller and Jastrow), that alive and active LMEV (succinate dehydrogenase, Hamel et al., 1990) and percentage of colonization by branch out manifold (Phillips and Hayman, 1980, described by Sieverding, 1983 and adapted for this crop, Sanchez et al. , 2010). The analysis of variance (SASR software version 9.1.3 ) showed that LMET, LMEV and % of branch out manifold showed highly significant differences between treatments. Greater LMET, coincided with increases in LMEV, colonization by branch out manifold and is presented in GC C, followed by AV, C and T, which did not vary among themselves, and, the lowest in CF. The coincidence of these three variables, would indicate that through LMET and especially, LMEV is absorbing and transporting P to the inside of the plants, and this supply, coinciding with higher % of colonization by branch out manifold, traces the path of the conjunction P in the soil-plantorganic fertilization, with their consequences on the economy of the agroecosystem and farmer.