Response of Plants to Azotobacter Inoculation

	Back to Home
Nitrogen Fixation in Free-Living and Associative Symbiotic Bacteria Nitrogen Fixing Bacteria Nitrogenase Genetics Mechanism of Nitrogen Fixation Response of Plants to Azotobacter Inoculation Nitrogen Fixation in the Root Zone of Rice

Response of Plants to Azotobacter Inoculation

Response of Plants to Azotobacter Inoculation
Inoculation of soil or seed with Azotobacter is effective in increasing yields of crops in well-manured soil with high organic matter content. Besides the ability to fix atmospheric nitrogen, Azotobacter is also known to synthesize biologically active substances such as B-vitamins, indole acetic acid and gibberellins in pure cultures.

The organism possesses fungistatic properties even on certain pathogenic species such as Alternaria and Fusarium. These attributes of Azotobacter explain the observed beneficial effects of the bacteria in improving seed germination, plant growth, plant stands and vegetative growth.

Abilities of seven strains of Azotobacter chroococuum isolated from the rhizosphere of sugarcane to fix nitrogen and produce indole compounds and gibberellin-like substances (GLS) in pure cultures (from D.L.N. Rao, 1975)

Strains	N₂ fixed mg/g sucrose utilised	μg IAA equivalents/ml culture filtrate	GLS (intensity of spots on paper chromatogram)
S1	10.64	205	+++
S2	6.16	4.0	++
S3	6.51	4.0	++
S4	8.50	5.0	+++
S5	6.72	3.0	+
S6	6.96	2.5	+++
S7	7.70	1.5	++

Several experiments conducted in temperate regions of the world show that nitrogen fixation in Azotobacter inoculated soils is not more than 10 to 15 kg of N/ha/year, depending on the availability of carbon sources.

Bacterial preparations containing Azotobacter cells under the name 'azotobacterin' were being produced and used in the erstwhile USSR and East European countries such as Czechoslovakia, Rumania, Poland, GDR, Bulgaria and Hungary where bacterization of seeds with azotobacterin has proved beneficial in increasing yields of crops such as wheat, barely, maize, sugarbeet, carrot, cabbage and potato.

The increase in yield of field crops was not more than 12% over corresponding uninoculated controls. Experiments with Azotobacter cultures and crop plants at the Indian Agricultural Research Institute, New Delhi, lead us to believe that significant increases in growth and yield of wheat, rice and vegetable crops could be obtained in pot trials.

However, under field conditions, such uniform trends towards increases in yield are not always reproducible. Apart form Azotobacter, bacteria like Beijerinckia and Derxia are also found to occur in tropical soils which are capable of fixing nitrogen but field experiments are needed before any conclusion could be made regarding their utility and benefits to crop production.

Effect of Azotobacterin on yield of field 9"Ops (from Mishustin and Shilnikova, 1969)

Crop	Average yield in control (metric cwt/ha)	Increase from Azotobacterin (%)
Spring wheat	15.8	8.2
Winter wheat	21.3	9.8
Oats	17.1	12.0
Barley	21.0	9.0
Maize	36.2	8.0
Sugarbeet	283.1	7.0
Potatoes	178.0	8.0
Average		8.86

The population of Azotobacter in the rhizosphere of crop plants and in uncultivated soil is generally low. Often inoculation of soil seed does not improve the situation. To overcome this limitation, repeated application of Azotobacter during different stages of growth of a crops is now being recommended with the object of increasing the number of bacteria in soil.

Some experiment son inoculation of soil with Azotobacter with different doses on inorganic N fertilizer have demonstrated the possibility of saving considerable amount of N fertilizer while still attaining desired yields of rice. Field trials with new and efficient cultures of Azotobacter have shown that the yields of sorghum, maize and cotton can be substantially increased by Azotobacter inoculation.

	Back to Home
Nitrogen Fixing Activity of Paddy Soil in Pots under Various Treatments Nitrogen Fixation in the Rhizosphere of Grasses and Weeds Associative Symbiosis Some New Nitrogen Fixing Bacterial Associations Several Nitrogen Fixing Bacteria Response of Plants Azospirillum Inoculation The Concept of C4 Dicarboxylic Acid Pathway Nitrogen Fixation by Rhizobium in a Free Living State

Home | Site map | Submit Article | Directory | Search