Soil microbes mediate biogeochemical cycling of essential nutrients (N, P, K, S) and assist in organic matter (OM) decomposition, preserving soil fertility and supporting plant productivity. Despite evidence, more research is needed on the soil-plant-microorganism (SPM) system with organic amendments. With the increasing interest in alternative plant nutrition methods, addressing this topic is justified. A potential alternative could be hydrochar (HC), a carbonaceous material obtained through the treatment of biomass viaa hydrothermal carbonization process. This study employs a multidisciplinary approach to examine the effects of chicken manure HC on the SPM system, evaluating soil microorganism abundance and activity, OM quality and quantity, nutrient availability, and sunflower plant performance under different irrigation conditions. HC was applied to a Cambisol at rates of 3.25 and 6.5 t ha-1 (HC-3.25, HC-6.5), with mineral fertilizer treatments providing equivalent total N contributions for comparison. Sunflower plants were grown in pots under two irrigation conditions (60% and 30% of the soil water holding capacity). Plants were harvested after 77 days, and macronutrient content in soil and plants was analyzed. The quality of OM was assessed using 13C NMR. Microorganism analyses included counting colony-forming units and using qPCR to measure 16S rRNA and ITS gene copies for bacteria and fungi, plus bacterial acid phosphatase (PHO), urease, and B-glucosidase (BG) gene copies. Microbial activity was evaluated by analyzing soil respiration and dehydrogenase, PHO, and BG activities. Results revealed that HC-6.5 treated soils had higher bacteria and fungi abundance and increased microbial activity. Particularly under well-irrigated conditions, these soils also exhibited a higher proportion of available K and S for plants, leading to improved nutrient uptake efficiency. Since the concentration of both elements did not rise after HC application at the beginning of the experiment, the availability changes are presumed to result from microorganism-mediated processes stimulated by HC. Our findings emphasize that HC amendment impact on soil involves interactions among climate, application rate, plant physiology, and microbial activity.

Resumen de la comunicación oral presentada en Centennial Celebration and Congress of the International Union of Soil Sciences held in Florence, Italy on May 19 - 21, 2024

Peer reviewed