Evaluation of Azotobacter strains for nitrogen fixation, survival, soil fertility, plant growth and nutrient uptake by maize (Zea mays L.)
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Date
2005-01
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Laboratory and greenhouse studies were undertaken to isolate, characterize and identify different strains of Azotobacter (AZO) isolated from soil. Relative performance of isolated strains and responses to inoculation with efficient Azotobacter strain and graded doses of fertilizer nitrogen with or without FYM addition were assessed in terms of plant height, fresh and dry weight of root and shoot of maize, N uptake, microbial population in soil and available N, P and K in soil at 60 and 70 days after sowing (DAS).
Based on cultural, morphological and biochemical characteristics, 19 strains of Azotobacter were isolated which differed in nitrogen fixing capacity to a great extent under bacteriologically controlled condition ranging from 1.79 to 9.84 mg N fixed per 25 mL broth culture, the maximum being with AZO-NMS4 strain which was about 8 times more than the lowest nitrogen-fixing AZO-NMS7 strain. The different strains of Azotobacter significantly increased plant height, fresh and dry weight of root and shoot, uptake of N, P and K by maize shoot, available NPK in soil and population of Azotobacter, actinomycetes and fungi in soil over the uninoculated control at 60 DAS. The numbers of low, medium and high responsive strains in terms of increased shoot dry weight were 2, 11 and 6 strains, respectively.
Inoculation with an efficient strain Azotobacter, FYM and graded doses of nitrogen in different combinations significantly increased plant height, fresh and dry weight of root and shoot of maize, uptake of nutrients, microbial population in soil and availability of N, P and K in soil at 70 DAS. Inoculation with Azotobacter alone, FYM alone and AZO+FYM significantly increased dry weight of maize shoot in successive significant manner which was 58.30 %, 138.47 % and 174.61 % more than the control, respectively. The maximum (328.53 % more than control) shoot dry weight was recorded with N-210 treatment which was statistically similar to AZO+FYM+N-80 treatment followed by AZO+FYM+N-60 treatment combination. Further, it has been recorded that AZO+FYM+N-60 treatment combination was statistically at par with application of N @ 120 kg ha-1 in increasing the majority of the parameters studied indicating a saving of 60 kg N ha-1 through the integrated use of biofertilizer, FYM and inorganic nitrogenous fertilizer for obtaining maximum and sustainable crop yield.
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