Microbial community dynamics and utilization of rhizodeposits and synthetic urine in grassland soils.

Microbial community dynamics and utilization of rhizodeposits and synthetic urine in grassland soils.

 Manisha Koirala ¹, Yang Ding ², Callum C. Banfield², Michaela A. Dippold² 

¹ Biogeochemistry of Agroecosystems, University of Göttingen, 37077 Göttingen, Germany

 

² Geo-Biosphere Interactions, University of Tübingen, 72076 Tübingen, Germany

 

Soil microbes thrive in a wide range of nutrient inputs and cope with an imbalanced supply of resources by adjusting their utilization strategies. In grasslands, animal urine and root exudates are essential drivers of C and macronutrient inputs and thus microbial growth and community composition, but little is known about how urine and exudates affect microbial community dynamics and utilization. In a factorial design, synthetic cow urine was applied to a Vertic Cambisol densely rooted by Dactylis glomerata. One day, four days, and 14 days after synthetic cow urine application, root-affected and not-rooted bulk soils were harvested. CFE microbial biomass, phospholipid fatty acids (PLFAs), DNA, and enzymatic activities were quantified to characterize the microbiome and its metabolic response.

Shoot biomass increased by 11%, 21%, and 36% at one, four, and 14 days after urine application compared to water application respectively. Root biomass increased by 4% and 9% after four and 14 days of water application, respectively, compared to urine application. In the root-affected soil, the activity of the enzyme acid phosphatase was 26%  higher 14 days after water application compared to that of urine. Conversely, the activity of the ß-glucosidase was 10% higher 14 days after cow urine application compared to water application in root-affected soil. Similarly, 14 days after urine application MBC in bulk soil was 84% higher compared to only water application. However, in the root-affected soils, MBC was 18% higher with water compared to urine application. The amount of DNA was also 0.5% higher 14 days after urine application compared to water application in the root-affected soils.

This study examined and compared the metabolic response of microbial communities and microbial community dynamics due to synthetic urine and water in bulk and root-affected soil. By approaching the study of soils from chemical as well as biological perspectives, an overview of microbial adaptation and structure can be gained to maintain healthy soil in grassland ecosystems.

Keywords: synthetic cow urine, grassland, soil microbial communities, root-affected soil, bulk soil, extracellular enzymes.