Greater Application of Nitrogen to Soil and Short-Term Fumigation with Elevated Carbon Dioxide Alters the Rhizospheric Microbial Community of xTriticocereale (Triticale): A Study of a Projected Climate Change Scenario

An attempt was made to understand the interactive consequences of subjecting a rhizospheric microbial community of xTriticocereale (Triticale) to higher CO2 levels and soil nitrogen addition in the short term in a tropical agro-ecosystem. Open-top chambers (OTCs) were used to grow the test crops for a single season under ambient CO2 (AC) and elevated CO2 (EC) along with two variable N dosages: recommended (N0: 0.053 g N/kg of soil) and high (N2: 0.107 g of N/kg of soil) levels. Variations in the composition of microbial communities and abundances were investigated using phospholipid fatty acid analysis (PLFA). A significantly (p < 0.001) increased microbial biomass content (MB) was observed under EC compared to AC, while the addition of N had a minor effect. A decreased fungi/bacteria (F/B) ratio (~38%) was observed with high N application in the CO2 enrichment treatment. Bacteria were more abundant, while fungal abundance decreased under N2 and EC. Gram (+ve) bacteria used these conditions to thrive under N2 and EC, while Gram (−ve) bacteria declined. No significant effects on actinomycetes were noticed in any of the treatments. However, eukaryotes acquired more benefits and flourished in response to EC. Varied responses were noted for the Shannon diversity index (H’) under EC. Overall, (i) bacteria (Gram-positive) and eukaryotes dominated under EC and high N addition, while fungi decreased, and (ii) EC and high levels of N addition did not affect actinomycetes. Short-term exposure under the given conditions was found to alter the rhizospheric microbial community. However, multiple season studies are needed to elucidate whether these short-term responses are transient or continuous.