Effects of Fertilizer from Hydrochar Septage on Growth and Physiological Responses of Miscanthus x giganteus and Spinacea oleracea

Although fertilizers help sustain agricultural production for the global population. The production of food comes at the expense of the environment and the benefits of its use are often minimized by the associated risks. Fertilizers do not only required high energy inputs but their excessive application in agriculture leads to several environmental problems including ground and surface water pollution and greenhouse gas (GHG) emissions. Therefore, alternative fertilizers that are able to provide crops enough nutrients while reducing their impact in the environment are necessary. The purpose of this study was to evaluate the effects of a novel organic fertilizer made out of domestic septage on biomass yields and physiological parameters including photosynthetic rates and leaf N content of an agricultural crop Spinacea oleracea (spinach) and a bioenergy crop Miscanthus x giganteus (miscanthus). The experiment consisted of a pot study in which plants were subject to different fertilizer treatments (synthetic nitrogen, phosphorus, septage hydrochar, a combination of synthetic nitrogen and phosphorus and an unfertilized control group). The miscanthus experiment was complemented by a field study that measured soil GHG fluxes and field biomass yields. For spinach, the effect of hydrochar in biomass yields was not significantly different from the other treatments, however, yields in the hydrochar group were 75% higher than the control group. Although hydrochar did not have a significant effect on photosynthetic rates and leaf N content, photosynthetic rates in the hydrochar group were 16% greater than the control group. For miscanthus, the hydrochar treatment produced higher biomass yields and photosynthetic rates than the rest of the treatments but differences between all treatments were not significant. Although hydrochar did not produce significant effects in spinach and miscanthus, the long-term source of nutrients from septage hydrochar could potentially be used in crops that do not require high available nutrient demand.