The Effect of Environmental Conditions on the Community Dynamics of Biofertilizer Microorganisms

Shannon Calder, Purdue University

Abstract

Biofertilizers are broths containing beneficial microorganisms that are applied to soils to enhance crop production and soil fertility. The microbes in a biofertilizer enhance and drive natural processes such as nutrient transformation and cycling, organic matter decomposition, and gas emission. Environoc 401 manufactured by Biodyne-USA is described as an agricultural soil enhancer that is comprised of a consortium of beneficial microorganisms. Production of Environoc 401 is achieved by an incubation that begins with a concentrated lyophilized microbial consortium. The focus of this study is to try to understand the community dynamics that occur during the incubation process to help predict the proportions of individual strains and the overall metabolic activity of the microbial community in Environoc 401 under different conditions. In order to quantify individual strains in Environoc 401, species-specific primers were developed for use in quantitative-PCR. These primers were then used to quantify target strains in Environoc 401 broth stored at 22 °C and 27 °C for 1 month and sampled at time 0, 1 week, and 1 month to evaluate the effect of storage conditions on the microbial community. In general, Environoc 401 stored at 22 °C had greater substrate utilization richness compared to Environoc 401 stored at 27 °C, but only after 1 month. The microbial community within Environoc 401 stored at 27 °C after 1 month did not utilize any amines or phenolic compounds, while the communities stored at 22 °C did use these substrates. To evaluate the overall effect of Environoc 401 on plants and on the microbial activity in potting medium, the product was used in the potting soil of soybean plants grown in an environmental growth chamber. This study contained five treatments upon unifoliate emergence: a no treatment control, pesticide and chemical fertilizer, pesticide and biofertilizer (as Environoc 401), biofertilizer only, and chemical fertilizer only. Soil medium samples were collected from each treatment at the time of seed planting, 24 hrs before application, 24 hrs after application, 2 weeks after application, and 1 month after application. The soybean plants treated with Environoc 401 generally had the highest average total plant height, average number of leaves, average dry weight of leaves, stems, and roots, and the least acidic pH. Samples from both studies were also used to inoculate Biolog EcoPlates to assess changes in carbon-source utilization patterns for each condition and to generate Community-Level Physiological Profiles (CLPPs). Principle Component Analysis was performed on the CLPPs and diversity was also assessed using Shannon’s diversity indices for samples from both studies. The CLPPs for the storage samples clustered tightly after 1 week of storage, however, after 1 month of storage the two temperatures diverged greatly. The CLPPS for the soybean plant treatment samples clustered tightly 24 hours prior to treatment but varied greatly after treatment application. These results indicate that treatment application, storage time, and temperature affect carbon utilization within the microbial communities. These results are a reflection on the activity and health of the microbial community and future studies should explore changes taking place on a finer scale by targeting specific carbon sources or conditions.

Degree

M.Sc.

Advisors

Soule, Purdue University.

Subject Area

Agricultural chemistry|Agronomy|Chemistry|Organic chemistry|Soil sciences

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