Utilization of Digestate as an Organic Manure in Corn Silage Culture: An In-Depth Investigation of Its Profound Influence on Soil's Physicochemical Properties, Crop Growth Parameters, and Agronomic Performance

The agricultural valorization of organic waste, including digestate from anaerobic digestion, can be a good tool to remedy the problem of soil depletion by intensive crops. This study was conducted to evaluate the effect of digestate application on the chemical characteristics of the soil, including N, P, and K content, pH, and electrical conductivity, as well as the agronomic performance of forage corn (Zea mays L.). Digestate was applied and incorporated into the soil at different rates (0; 0+ recommended NPK rates; 15, 30, and 60 t dry weight (DW) ha(-1)). Digestate application at increasing doses improved soil chemical characteristics at harvest, and the application of 15, 30, and 60 t DW ha(-1) significantly decreased soil pH by 0.15, 0.23, and 0.39 units, respectively. For electrical conductivity, the average values recorded are 196, 212, and 255 uS m(-1), respectively, to 15, 30, and 60 t DW ha(-1) doses. A significant organic matter enrichment of the topsoil layer was observed only for treatments receiving 30 and 60 t DW ha(-1). Similarly, our results showed that the N, P, and K contents increased significantly with digestate application at both rates compared to the positive control. Morphological characteristics of the corn plants (height, leaf number, and collar diameter) and ecophysiology (stomatal conductance and chlorophyll) increased in a global manner compared to the negative control. Indeed, the obtained results showed that this improvement was not proportional to the applied doses for all analyzed parameters. However, there was no significant difference between the obtained values in amended plants with 15 t DW ha(-1) and those in the positive control (recommended dose in NPK). In comparison to this previous one, height, leaf number, and collar diameter increased by 15%, 13%, and 20%, respectively, with a 30 t DW ha(-1) dose and by 34%, 20%, and 24% with a 60 t DW ha(-1) dose. Concerning the relative chlorophyll content and stomatal conductance, the values recorded in the plants amended with 60 t DW ha(-1) are 1.7 and 2.2 times higher compared with the positive control. The fresh biomass, dry biomass, and root length parameters increased proportionally to the applied dose.