Ms Aliia Gilmullina^1,2, Dr. Cornelia Rumpel³, Dr. Evgenia Blagodatskaya^4,5, Dr. Abad Chabbi^1,2

¹UMR P3F, INRA, Lusignan, France, ²UMR ECOSYS, INRA, THIVERVAL GRIGNON, France, ³Institute of Ecology and Environmental Sciences- Paris (iEES-Paris) UMR CNRS, INRA, UPMC, THIVERVAL GRIGNON, France, ⁴Agro-Technology Institute, RUDN University, Moscow, Russia, ⁵Dept. of Soil Ecology, Helmholtz Centre for Environmental Research – UFZ, Halle (Saale), Germany

Despite the need for the adoption of soil organic C (SOC) sequestering management practices to improve soil quality and contribute to climate change mitigation, little is known about the effect of grazing versus mowing on properties of grassland soils. Here, we sampled soil from two depths at an experimental site in Western France, which had been since 14 years under grazing or mowing regimes. We aimed to assess the effect of the two management practices on soil organic matter (SOM) quantity, quality and microbial functioning. To this end we analysed for elemental concentrations, specific SOM compounds (lignin and non-cellulosic polysaccharides) and microbial biomass, microbial growth kinetics and 9 extracellular enzymes activities.

We found nearly two times higher SOC under grazing compared to mowing. The chemical composition of SOM in topsoil differed between treatments with lower contribution of lignin and higher contribution of microbial biomass under grazing treatment. Lignin content was higher under mowing while both treatments showed similar non-cellulosic polysaccharides contents. Difference in enzymes activities between treatments were only observed after normalisation by microbial C, indicating more efficient enzyme production under grazing. We conclude, that the presence of animals under grazing most probably caused relative domination of r-strategists in microbial community leading to SOC accrual via enhanced substrate availability and high microbial use efficiency, whereas under mowing poor nutrient conditions favoured K-strategists and led to lower microbial activities.

Biography: Aliia Gilmullina is a PhD student at French agricultural research institute (INRA). Her thesis deals with the issue of SOM quality and quantity impacted by grassland management practices. She is particularly interested in the investigation of microbial contribution to SOM.