Bacteriophages of Nitrogen-Cycling Bacteria and Engineered Biochar for Reducing Nitrogen Losses

Abstract

The emission of Greenhouse gases (GHG) from agriculture is a huge problem. Nitrous oxide (N2O) has a higher Global Warming Potential (GWP) than all other gases. The increased use of nitrogen fertilizers since the Green Revolution has intensified this issue, as lower Nitrogen Use Efficiency (NUE) results in nearly half of the applied nitrogen being lost through nitrate leaching, ammonia volatilization, and N2O emissions. This study aims to mitigate N2O emissions by controlling the rate of nitrification. The firststrategy involved isolating the nitrifying bacteria (Nitrosomonas europaea) from active agricultural soil and its bacteriophage from sewage samples. The second strategy focused on the application of nitrogen-loaded biochar and sorghum extract-treated nitrogen-loaded biochar as biological nitrification inhibitors in a pot experiment with maize (Zea mays). Biochar (a carbon-rich compound) was loaded with nitrogen at three different levels (50kgha-1 , 100 kgha-1 , 150 kgha-1 ). In another set, biochar was first treated with sorghum extract and then loaded with nitrogen at the same three levels. A maize Pot experiment was conducted to measure morphological parameters, study nutrient dynamics in soil and plant uptake, assess /photosynthetic parameters. The phylogenetic analysis of isolated bacteria confirmed their similarity to Pseudomonas spp., and a bacteriophage against this bacterium was isolated with positive results from the spot assay. The results of the biochar maize study revealed a 98.54% increase in shoot biomass with 100 kg/ha nitrogen-treated biochar and a 14.58% to 24.01% increase in plant height with 150 kg/ha nitrogen-treated biochar, compared to the control.while sorghum extract-doped nitrogen-treated biochar increased root biomass. The interaction of sorghum extract with nitrogen-loaded biochar significantly enhanced photosynthetic activity in maize, whereas nitrogen-treated biochar alone did not produce this effect. Soil extractable potassium was significantly increased by nitrogen-treated biochar while the organic solution has significantly reduced extractable potassium. Nitrogen-loaded biochar and organic solution have no significant effect on total phosphorus. However, their interaction has significantly reduced total phosphorus. Nitrogen-loaded biochar as well as organic solution (Sorghum extract) doped N-loaded biochar have significantly improved the Soil NO3 and ammonical nitrogen. xxii In summary, nitrogen-loaded biochar, especially when treated with sorghum extract, shows promise in enhancing plant growth parameters, photosynthetic activity, and nutrient uptake, while contributing to the mitigation of N2O emissions from agricultural sector.