Abstract
Exploration of diverse environmental samples for plant growth-promoting microbes to fulfill the increasing demand for sustainable agriculture resulted in increased use of bacterial biofertilizer. We aimed for the isolation of plant growth-promoting as well as antibiotic sensitive bacteria from bovine manure samples. The basic theme of our study is to highlight potentials of bacteria in manure and the unchecked risk associated with the application of manure i.e. introducing antibiotic-resistant microbial flora, as fertilizer. Fifty-two, morphologically distinct isolates; from eight different manure samples, were subjected to plant growth-promoting parametric tests along with antibiotic resistance. Thirteen antibiotic sensitive bacterial strains with potentials of plant growth promotion further characterized by 16S rRNA ribotyping and the identified genera were Stenotrophomonas, Achromobacter, Pseudomonas, and Brevibacillus. Successful radish seeds germination under sterile in-vitro conditions showed the potential of selected bacterial isolates as plant growth-promoting bacteria. The results of this study confirmed plant growth-promoting characteristics of bovine manures’ bacterial strains along with an alarming antibiotic resistance load which comprises 75% of bacterial isolated population. Our study showed distinct results of un-explored manure bacterial isolates for plant growth promotion and flagged ways associated with unchecked manure application in agriculture soil through high load of antibiotic resistant bacteria.
Highlights
Animal manure is undigested components of animal feed, enriched with 55 to 95% of nitrogen and 70% of phosphorus ingested, excreted in manure [1]
Samples of Nili Ravi (Water buffalo) dung from the village farm resulted in the maximum number of bacterial isolates while the sample of cow dung from town farm resulted in the least number of strains
The results obtained from in-vitro experiments i.e. Indole acetic acid (IAA) production, putative nitrogen fixation, phosphorus, potassium, zinc, calcium, magnesium solubilization along with Hydrogen cyanide (HCN) production, supports our hypothesis
Summary
Animal manure is undigested components of animal feed, enriched with 55 to 95% of nitrogen and 70% of phosphorus ingested, excreted in manure [1]. The livestock products are macroand micronutrient enriched sources and supplies 18% food energy [2,3]. The application of manure in agricultural land provides several benefits like nutrient recycling, better crop productivity, and improved organic matter [4]. Reduced soil erosion and increased water holding capacity improves soil water availability for cultivation [5]. In an eight-year field study [6] of applying chemical fertilizers (NPK) and manure mixed chemical fertilizers explores agricultural benefits of comparative fertilization. Application of NPK-manure mixes increased soil fertility, crop yield over non-manure NPK mix fertilization.
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