Comparison of Effects of Chemical and Food Waste-Derived Fertilizers on the Growth and Nutrient Content of Lettuce (Lactuca sativa L.)

The current high rate of food waste production, concomitant with the global increase in population and food demand, has adverse effects on environmental and socio-economic conditions. However, food waste has been shown to be an efficient and safe source of fertilizer in agriculture practice. Moreover, minimizing the application of chemical fertilizers is a goal of sustainable agriculture. Considering these facts, we aimed to compare the effect of chemical fertilizer (CF-3,8 g&middot:pot&minus:1) and different doses of mixed food waste-derived fertilizer (MF-10.6 g&middot:pot&minus:1), two-fold MF (MF &times: 2), four-fold MF (MF &times: 4), and six-fold MF (MF &times: 6) in a popular salad crop, Lactuca sativa (lettuce). Our results showed the growth rates of lettuce plants receiving CF, MF, and MF&times:2 applications were essentially the same: however, plant biomass significantly dropped with MF &times: 6 treatment. The CF, MF, and MF &times: 2 treatments enhanced the chlorophyll content, chlorophyll fluorescence, and photosynthetic rate of the plants and improved transpiration efficiency and stomatal conductance. With respect to mineral elements, the K+ content was significantly enhanced with MF &times: 2 and MF &times: 4 treatment, whereas MF &times: 6-treated plants showed lower concentrations of Ca, P, Mg, and K+ as well as higher Na+ concentration. Biochemical analysis showed the elevation of abscisic acid level with increasing dose of MF, except in the MF &times: 6 treatment. The level of super oxide dismutase (SOD) dropped with CF treatment, was unchanged with MF, and significantly increased in MF&times:2 and MF &times: 4 treated plants. Subsequently, higher flavonoid content was observed in MF&times:2 and MF&times:4 plants. The current results demonstrate the potential of food waste as a source of organic fertilizer and a significant substitute for chemical fertilizer in the conventional agricultural practice driven by high production cost and environmental pollution.