Effects of agrochemicals on phosphate solubilizing and nitrogen fixing bacteria associated to peanut crop

ANZUAY, S.; GHIO, S.; ANGELINI, J.; TAURIAN, T.; FABRA, A.

Villa Carlos Paz

Congreso; Congreso Argentino de Microbiología General; 2009

In Argentina, peanut crop production is concentrated in Cordoba province. Intensification of agricultural practices in this area has led to excessive use of agrochemicals. It is well known that plant growth promoting bacteria inhabiting agricultural soils can be affected by the application of these substances. The understanding of soil bacteria diversity and its response to the agrochemical application is necessary in order to implement friendlier practices in agriculture. The aim of this study was to analyze the effect of agrochemical application on nitrogen fixing and phosphate solubilizing bacteria associated to peanut crop. Two soil samples of a peanut cultivated field were used in this study: a soil sample without application of agrochemicals (control) and one where herbicides were introduced (treated soil). Total cultivable bacteria grown in TSA medium, number of phosphate solubilzing bacteria in NBRIP-BPB medium and nitrogen fixation bacteria in NFB and JNF media were determined in both soil samples. Results demonstrated that number of heterotrophic and phosphate solubilizing bacteria was not altered by agrochemicals application while nitrogen fixing bacteria´s number decreased in treated soil sample. Neverheless, even when number of heterotrophic and phosphate solubilizing bacteria was not affected by agrochemicals application, an increase in the proportion of gram positive bacteria in this population was determined. It is possible to conclude that herbicides application in peanut crop fields cause changes in agronomically important microbial population.