Synergistic Effects of Diazotrophic Phosphate Solubilizing Azotobacter chroococcum and AM Fungus Glomus mosseae on Yield Improvement in Finger Millet (Eleusine Coracana (L.) Gaertn.)
Abstract
Field experiments were conducted to study the response of finger millet Eleusine Coracana (L.) Gaertn. to combined inoculation with the P-solubilizing diazotrophic Azotobacter chroococcum (DT) isolated from the rhizosphere of finger millet and the P-mobilizing Arbuscular Mycorrhizal fungus Glomus mosseae under graded levels of N & P fertilizers (100, 75 and 50 percent).The inoculated seedlings were transplanted to the laid out plots (RCBD) with red sandy loam soil having medium levels of NPK and OC. The combined inoculation resulted insignificant increase in yield overall the other treatments with 31.00, 27.99 and 18.10 percent grain yield and 36.69, 33.55 and 15.01 percent straw yield respectively in presence of 100, 75 and 50 percent N and P fertilizers in comparison with uninoculated control indicating efficient N supplementation and P-solubilization by A. chroococcum and P-mobilization by the AM fungus. The results indicated that 25-50 percent of N and P fertilizers can be curtailed in presence of combined inoculants, saving money without decrease in the yield performance of finger millet. The combination of these inoculants can be included as one of the important agronomic inputs in finger millet cultivation both under subsistence and affluent farming systems.
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Introduction
Finger millet (Eleusine Coracana (L.) Gaertn.) popularly known as ragi is one of the important minor millets grown in India and ranks second in importance among the millets cultivated in India assuming growing importance due to its dietary role among rural folk and the diabetics. The crop is grown in 2.5 million hectares in the country and Karnataka ranks first with an area of 0.99 m. ha under ragi cultivation 1. To a large extent, the finger millet is cultivated by poor and marginal farmers under subsistence farming with low nutrient input. Nitrogen and phosphorus determine the yield in combination with potash. However, the soils grown for ragi are of low fertility soils resulting in wide regional variations in yield averaging 1500-1700 kg/ha as against the varietal potential of 4000 to 5000kgs. Nitrogen fixing Bacteria (NFB), phosphate solubilizing bacteria (PSB) and Arbuscular Mycorrhizal Fungal (AMF) inoculants playa major role in supplementing and mobilizing these nutrients to plants under low input conditions while reducing their application under affluent farming systems. To harness the synergistic effects, these three groups of inoculants have to be used in combination which is not a common practice among farmers. However, this problem can be solved to a great extent by using bacterial isolates which perform both the functions of nitrogen fixation and phosphate solubilization. In nature there exist bacteria which perform dual functions of nitrogen fixation and phosphate solubilization in a single application. Such phosphate solubilizing diazotrophs among Azotobacter, Bacillus and Azospirillum species have been reported from the rhizosphere of plants Halder et al., 2, Abd alla 34, Sheshadri et al., 5; Vivek Kumar et al.,6; Monica et al.,7; Rahim et al., 8 and Hafsa et al.,9. Chandana and Venkataramana 10 isolated and evaluated phosphate solubilizing diazotrophic Azotobacter chroococcum and Bacillus sp. from the rhizosphere of finger millet with significant grain and straw yield improving influences. A few reports are available on the effects of tripartite inoculation of NFB, PSB and AMFs with encouraging results 11. However there is lack of information on the synergistic influences of phosphate solubilizing diazotrophic Azotobacter chroococcum in combination with AM fungus Glomus mosseae on finger millet. The present study reports for the time the growth and yield response of finger millet to the combined inoculation with phosphate solubilizing diazotrophic Azotobacter chroococcum (DT) in combination with AM fungus Glomus mosseae.
