Microbial abundance in sugar beet rhizosphere inoculated with azotobacter chroococcum

Abstract

Rhizosphere appears as the most important niche for microbial activity. It is of direct relevance to nutrient cycling affecting plant nutrition. Rhizosphere can be defined as the root surface and the soil adhering to the root. The aim of this research was to determine the effect of inoculation with Azotobacter chroococcum on the number of microorganisms in the rhizosphere of sugar beet in dependence of fertilization. Field trials were conducted on a chernozem soil at the Rimski Šančevi Experiment Field of the Institute in 2002, 2003 and 2004. The sugar beet hybrid variety Sara was used. Inoculation of sugar beet was performed with a liquid culture of Azotobacter chroococcum strains, which was incorporated into the soil just before planting in the concentration of 109/ml. Differences were registered in population size depending on both the nitrogen dose and fertilisation method. On average, a higher percentage of increase was in the total number of microorganisms (35-118%) than in azotobacter population size (49-52.8%).

Cilj ovih istraživanja bio je utvrđivanje uticaja inokulacije sa azotobakterom na brojnost mikroorganizama u rizosferi u zavisnosti od doze azota i vrste đubrenja kod šećerne repe. Poljski ogledi su izvedeni u toku 2002, 2003. i 2004. godine na Rimskim Šančevima sa hibridnom sortom Sara stvorenom u Institutu za ratarstvo i povrtarstvo. U radu je određivan ukupan broj mikroorganizama na zemljišnom agaru (razređenja 106), broj gljiva na Čapekovom agaru (razređenja 104), aktinomiceta na sintetičkom agaru (razređenja 104) i azotobaktera na podlozi Fjodora (razređenja 102). Inokulacijom je povećan ukupan broj mikroorgainazama (35-118%), broj azotobaktera (49-52,8%), i gljiva (7,5-19,7%). Broj aktinomiceta je smanjen inokulacijom (1,6-5,4%). Najveći broj azotobaktera dobijen je na varijanti bez dodatka azota, a najmanji sa 200 kg N/ha. Najveći broj gljiva dobijen je sa 100 kg N/ha, a aktinomiceta sa 150 kg N/ha.