Effect of Azotobacter croococcum on productive traits and microorganisms in sugar beet rhizosphere

Abstract

The aim of this study was to determine the effects of three different inoculation methods with selected Azotobacter chroococcum strains on productive and technological traits of sugar beet, as well as on the total number of microorganisms and azotobacter in rhizosphere. The results of this two-year study showed that effectiveness of the tested inoculation methods in increasing root yield and sugar content varies greatly, depending on year and azotobacter strains. Effectiveness of inoculation methods was not largely impacted by year on granulated sugar. Achieved granulated sugar yield was significantly higher by using pre-sowing azotobacter application, than by using seed inoculation. A significantly increased number of microorganisms in sugar beet rhizosphere was determined, not only by using pre-sowing azotobacter application but also by using sugar beet seed inoculation. Pre-sowing azotobacter application and inter-row cultivation both caused an equal increase in the number of these bacteria in sugar beet rhizosphere (42.2% and 46.9%). Use of sugar beet seed inoculation caused an increase of 33.7% in the number of azotobacter. In order to achieve higher effectiveness in applying azotobacter on productive and technological traits of sugar beet, and considering determined interaction between a certain year, an inoculation method and a strain, it is necessary for future research to focus on determining efficiency of these strains when they are in a mixture.

Cilj ovog rada je utvrđivanje uticaja tri različita načina inokulacije sa sojevima Azotobacter chroococcum na proizvodne i tehnološke osobine šećerne repe i ukupnu brojnost mikroorganizama i brojnost azotobaktera u rizosferi. Na osnovu dvogodišnjih istraživanja utvrđeno je da je efektivnost ispitivanih načina inokulacije na povećanje prinosa korena i sadržaj šećera značajno varirala u zavisnosti od godine i soja azotobaktera. Uticaj godine na efektivnost inokulacije azotobakterom nije bio od većeg značaja za prinos kristalnog šećera. Pri inkorporaciji azotobaktera neposredno pre setve ostvaren je značajno bolji prinos kristalnog šećera u poređenju sa inokulacijom semena. Utvrđena je značajno povećana brojnost mikroorganizama u rizosferi šećerne repe pri inkorporaciji azotobaktera neposredno pre setve i inokulacijom semena šećerne repe. Inkorporacija azotobaktera neposredno pre setve i prvog međurednog kultiviranja uslovila je podjednako povećanje brojnosti ove bakterije u rizosferi šećerne repe (42,2% i 46,9%). Inokulacijom semena šećerne repe ostvareno je povećanje brojnosti azotobaktera za 33,7%. S obzirom da je u radu utvrđena interakcija između godine, načina inokulacije i soja, a u cilju postizanja veće efektivnosti pri primeni azotobaktera na proizvodne i tehnološke osobine šećerne repe, neophodno je buduća istraživanja usmeriti ka utvrđivanju efektivnosti ovih sojeva kada su u smeši.