Hairy vetch (Vicia villosa Roth) is an annual legume cover crop that is winter hardy throughout Korea if established in a timely manner. Hairy vetch can fix large amounts of nitrogen, with biological nitrogen fixation through symbiosis with rhizobacteria.
This study was conducted to select rhizobia from hairy vetch (Vicia villosa Roth) with nodulation and excellent nitrogen-fixing ability. Hairy vetch root was collected from 7 of cultivation region of all over the country, rhizobia were isolated from the root nodules. Isolates were re-inoculated into a hairy vetch separately and studied nodulation and nitrogen-fixing ability. As a result, total of 52 Rhizobium sp. isolates were isolated from the hairy vetch root nodules, among these, 16 isolates were Rhizobium sp. which show good growth at more than 0.5% NaCl concentration. These 16 isolates were re-inoculated separately, 8 weeks after, good root nodule formation was observed from Rhizobium sp. RH1, RH3, RH81, RH82, RH84, and RH93 strain treated samples. 6 isolates were positive for nitrogen fixing ability, the highest acetylene reduction activity was shown by Rhizobium sp. RH84.
Rhizobium sp. RH84 was gram negative, rod shape and has 2~3 flagella. Colonies of RH84 were having sticky appearance showing the production of mucous. Analysis of colony morphology indicated round colonies, white~milky white colored. The optimum culture conditions were using 2% soybean carbon source at 28oC. The Rhizobium sp. RH84 was sensitive to the antibiotics (streptomycin 25 ppm). Rhizobium sp. RH84 to produce acid, akaline phosphatase and β-galactosidase during growth. For the investigation of plant growth promoting effects by the Rhizobium sp. RH84, production of indole acetic acid (IAA), siderophore, phosphate solubilization and nitrogen fixation were tested and other characters were examined. As results, Rhizobium sp. RH84 produced 9.03 ug IAA per mL and showed nitrogen fixation activity.
Different adhesives (arabic gum (AG) and carboxymethyl cellulose (CMC)) and covering materials (bentonite, kaoline, phyrophylite, perlite) were tested for seed coating. CMC was good adhesive and the optimum concentration for germination of seed was 1%. Perlite was the best covering material for RH84 stability of temperature (4oC, R/T, 28oC) during 6 months.
The effect of application of gypsum (CaSO4?2H2O) and rice hull were treated to reclaimed land soil with RH84. Treatment with two soil conditioner and with Rhizobium sp. RH84; conditioner control, gypsum, rice hull, gypsum+rice hull, Rhizobium sp. RH84 control, Rhizobium sp. RH84+gypsum, Rhizobium sp. RH84+rice hull, Rhizobium sp. RH84+gypsum+rice hull. At 2 weeks later, hairy vetch seed germination was in the order control>rice hull>rice hull+gypsum>gymsum regardless treatment of Rhizobium sp. RH84. At 8 weeks later, hairy vetch fresh weight was in the order gypsum>control>rice hull and growth was Rhizobium sp. RH84 treatment groups better than untreated. But, the limit on the salt concentration was difficult to overcome. So, to overcome the soil organic matter content, we used media. Commercial media and reclaimed land soil mixed (9:1, 7:3, 5:5, 3:7, 1:9) and treated with 0.3% NaCl. Growth of hairy vetch in 9:1 and 7:3 were increase than that 5:5, 3:7 and 1:9. These results indicate that importance of salt concentration as well as the soil physical properties.
ACC (1-aminocyclopropane-1-carboxylate) deaminase can cleave the plant ethylene precursor ACC, and thereby lower the level of ethylene in a developing or stressed plant. So, hairy vetch seed treated two complex strains (rhizobium and ACC deaminase activity strain) and seeded on high salinity of the reclaimed land soil. As a result, hairy vetch seed was germinated normally in 0.5% NaCl in growth over the limit concentration 0.2%. And this result will be contributed to fertilization of high salinity reclaimed land.
Field experiments were conducted in 2011 on a fertile soil and reclaimed land soil. Hairy vetch (Vicia villosa Roth) seeds were coated with 1% CMC and Rhizobium sp. RH84 (109 cfu/ml), and beds on October 2011 and May 2012. Two treatments were compared: none and Rhizobium sp. RH84 treatment. As a result, fresh weight was significantly higher for Rhizobium sp. RH84 treatments. From these results suggest that the Rhizobium sp. RH84 can be use the possibility of its application as a green manure crop of hairy vetches in nonuniform salt distribution reclaimed land.