González Vázquez, Mariela

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    Poblaciones de microorganismos asociados a la Rizósfera del cultivo de la calabaza (Cucurbita moschata Dutch.) durante un programa de agricultura sustentable
    (2005) González Vázquez, Mariela; Chavarría Carvajal, José A.; College of Agricultural Sciences; Rosa, Evelyn; Flores, Carlos; Department of Crops and Agro-Environmental Sciences; Alameda Lozada, Myrna Z.
    Pumpkin (Cucurbita moschata Dutch), is the most economically important vegetable in Puerto Rico. During the period 2003-2004 the production was 285,903 hundredweights (cwt.), with a farm value of $ 5.8 millions. Methyl bromide (CH3Br) is a gaseous fumigant used worldwide as soil disinfectant, previous to the seeding of many crops like vegetables and fruits. Recently the used of this chemical have been questioned, due to that depletes the ozone cap of the Earth. For this reason the search of new alternatives to methyl bromide that are not hazards for the environment has been intensified. Some of these alternatives include the combination of techniques such as crop rotation, organic amendments and solarization. During the study of new alternatives is important to follow the changes in populations levels and frequency of the microorganisms associated to the rhizosphere of the main crop. The treatments evaluated were: T1. Corn (var. ‘‘Mayorbela’’) plus a cycle of pumpkin; T2. Velbetbean (Mucuna deeringiana) plus a cycle of pumpkin; T3. Soil incorporation of organic matter (7.3 kg/plant of poultry litter) plus two cycles of pumpkin; T4. Soil solarization (120 days) plus a cycle of pumpkin; T5. Chemical control (Nemacur 15 G 3.0 g a.i./plant) plus two cycles of pumpkin; and T6. Absolute control (two cycles of pumpkin). For the isolation of fungi and bacteria 10-g soil from each treatment was used to prepare serial dilutions to 10-4. Rose Bengal Sreptomycin Agar was used for the isolation of fungi. Total bacteria population was isolated in Tryptic Soy Agar (TSA 5 %). Also, selective media and a chitin- amended media were used for the isolation and identification of fungi and bacteria. Differences between treatments were observed when the means were compared using LSD P 5 0.05. The most frequently isolated chitinolytic-fungi were Aspergillus flavus, A. terrus, Humicola spp.y Trichoderma spp. After the use of crop rotation, organic amendments and solarization, bacterial composition changed to a predominant Gram positive population. Therefore, the sustainable agricultural practices changed the soil microflora, diversifying it and increasing its population levels.