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Hairy vetch (Vicia villosa Roth) is a leguminous cover crop that is generally used as a green manure to sustain soil health in arable land. Molybdenum (Mo) acts as a cofactor for the nitrogenase (NA) and nitrate reductase (NR) enzymes, which are important for nitrogen (N) fixation, nitrate reduction and N transport in plants. In this study, we applied various doses of Mo to soil to evaluate their efficacy on nodulation, nodule characteristics and biomass production of hairy vetch. Mo application increased the number and size of nodules and NA and NR enzyme activity in hairy vetch. This increase in enzyme activity increased N assimilation and led to higher biomass yield. Plants grown in soil that received 0.5 mg Mo kg −1 showed optimal physical and biochemical properties in nodules, and these properties may explain the increased N fixation in hairy vetch. Higher Mo doses (1.0 mg kg −1 ) led to the deterioration of nodule structure and, hence, reduced enzymatic activity in plants. The 16S rRNA gene sequencing and cluster analysis showed that the bacterial isolates found in the nodules of hairy vetch roots belonged to the Rhizobiaceae family and shared high sequence similarity with Rhizobium leguminosarum and Agrobacterium tumefaciens. Application of 0.63 mg Mo kg −1 to soil was the optimum dose to maximize the biomass yield of hairy vetch.

Livestock manures are broadly used in agriculture to improve soil quality. However, manure application can increase the availability of organic carbon, thereby facilitating methane (CH4) production. Cattle and swine manures are expected to have different CH4 emission characteristics in rice paddy soil due to the inherent differences in composition as a result of contrasting diets and digestive physiology between the two livestock types. To compare the effect of ruminant and non-ruminant animal manure applications on CH4 emissions and methanogenic archaeal diversity during rice cultivation (June to September, 2009), fresh cattle and swine manures were applied into experimental pots at 0, 20 and 40 Mg fresh weight (FW) ha−1 in a greenhouse. Applications of manures significantly enhanced total CH4 emissions as compared to chemical fertilization, with cattle manure leading to higher emissions than swine manure. Total organic C contents in cattle (466 g kg−1) and swine (460 g kg−1) manures were of comparable results. Soil organic C (SOC) contents were also similar between the two manure treatments, but dissolved organic C (DOC) was significantly higher in cattle than swine manure. The mcrA gene copy numbers were significantly higher in cattle than swine manure. Diverse groups of methanogens which belong to Methanomicrobiaceae were detected only in cattle-manured but not in swine-manured soil. Methanogens were transferred from cattle manure to rice paddy soils through fresh excrement. In conclusion, cattle manure application can significantly increase CH4 emissions in rice paddy soil during cultivation, and its pretreatment to suppress methanogenic activity without decreasing rice productivity should be considered.

Aim: Potassium (K) is one of the three major nutrients required of plant growth and muriate of potash (MoP) is the only recognized chemical fertilizer used in agriculture. In many countries, 100% of the applied MoP is imported costing huge revenue. Application of suitable potassium-solubilizing bacteria (KSB) as biofertilizer could be an integral part of K management in arable soil. The object of this study was to evaluate K-solubilizing ability of a ubiquitous micro-organism as KSB to supplement K in soil. Methods and Results: Strain (O-5) was isolated from tea-growing soil and identified as Bacillus pseudomycoides. Phylogenetic analysis revealed that the nearest neighbours of B. pseudomycoides strain O-5 were Bacillus cereus, Bacillus thuringiensis and Bacillus toyonensis. Though the species was first identified in 1998 and is ubiquitous in soil, the role of this group of micro-organisms in nutrient cycling in soil has not been studied before. Strain solubilized 33Á32 AE 2Á40 lg K ml À1 in mica waste (MW; muscovite type mineral)-amended broth after 7 days incubation at 30 AE 1°C. In a soil microcosm study under laboratory condition, B. pseudomycoides strain O-5 increased K availability by 47Á0 AE 7Á1 mg kg À1 after 105 days incubation, while the strain released 104Á9 AE 15Á3 mg K kg À1 in MW-treated soil. In this study, application of isolated B. pseudomycoides with MW significantly increased K availability in soil, and that in turn facilitated K uptake by tea plants. Conclusion: Based on the data, it could be inferred that B. pseudomycoides could mobilize K from bound form in soil and can be utilized as K-solubilizing biofertilizer especially in combination with MW for supplementing K in soil. Significance and Impact of the Study: Bacillus pseudomycoides strain O-5 has potential to be used as K-solubilizing biofertilizer in agriculture.

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