Abstract
A study was conducted for isolation and screening of effective Azotobacter strains and their performance in different agro-ecological regions (AEZs) of Bangladesh to develop Azotobacter biofertilizer technology package for wheat cultivation. Eighteen isolates of Azotobacter chroococcum were obtained from rhizosphere soils of wheat from three AEZs of Bangladesh. Five isolates were screened out as better strains through different laboratory tests. The soils of AEZ 1 showed the highest population of Azotobacter followed by the soils of AEZ 11 and AEZ 9. Higher population of Azotobacter was recorded in rhizosphere soil over non-rhizosphere soil in wheat fields. The performance of five Azotobacter isolates were evaluated in pot as well as in field with corresponding five levels of N fertilizer (0%, 20%, 40%, 80% and 100%N). The yield and yield contributing characters and nitrogen uptake of wheat were increased due to Azotobacter inoculation compared to uninoculated control treatment. Azotobacter strains At₂, At₈ and At₁₅ performed better compared to At₃ and At₇ in respect of growth, yield attributes and yield of wheat both in pot and field conditions. Nitrogen application showed improvement in growth, yield and yield contributing parameters of wheat. Nitrogen in graded levels (0%, 20%, 40%, 80% and 100%N) along with Azotobacter inoculation exhibited higher growth, yield and yield attributes as well as N uptake in wheat over uninoculated control. The 80%N along with inoculants At₂, At₈ and At₁₅ showed similar yields compared to that of 100%N applied alone in both pot and field conditions. The performance of three Azotobacter strains either singly or in mixed culture along with five levels of N was tested in four AEZs of Bangladesh. The performance of three strains as single culture on growth, yield and yield contributing characters and N uptake by wheat was better than the mixed culture inoculant. The survival of Azotobacter cells in peat carrier prepared from three Azotobacter strains was tested under four storage conditions in the laboratory. All the single and mixed inoculants showed survival of more than 5×10⁶ cells g⁻¹ peat inoculant up to five months at room temperature and incubator, six months in cold storage and seven months in refrigerator. The results as obtained from pot and field study revealed that Azotobacter strains At₂, At₈ and At₁₅ can be used as inoculant for wheat cultivation in Bangladesh.