Mitigating carbon footprint: Integrating nitrified urine fertilizer in two hydroponic tomato cultivation systems

Abstract

The replacement of mineral fertilizers with recycled nutrients from waste streams addresses the pressing need to reduce crop production carbon footprint. Recent research has demonstrated the successful use of nitrified human urine fertilizers in hydroponic tomato cultivation. However, regarding the accumulation of ions such as Na Cl + and , the feasibility of their use in commercial greenhouse production systems has not yet been evaluated. Our study aimed to assess the influence of nitrified urine fertilizer on plant physiology, product quality, fertilizer use and greenhouse gas emissions from the rootzone for recirculating hydroponic systems. In a two-factorial experiment, tomatoes (Solanum lycopersicum cv. ‘Avalantino’ F1) were cultivated in a recirculated nutrient so lution using drip irrigation on rockwool or nutrient film technique. Two nutrient solution treatments were applied: one containing calcium-rich nitrified urine fertilizer along with mineral fertilizers, and another based solely on mineral fertilizers serving as the control treatment. Our findings demonstrate that tomatoes can be grown in recirculating hydroponic systems using nitrified urine fertilizer without experiencing significant yield reductions. The urine fertilizer solution was discarded twice at a sodium concentration of 12 mM. No significant differences in nitrous oxide (N 2 O) emissions and total contents of secondary metabolites in fruit were observed between the fertilizer treatments. In the nitrified urine treatments, high sodium and calcium concentrations did not affect potassium nutrition, but high calcium concentrations necessitated higher magnesium supply. 94% of nitrogen, 13% of potassium, and 7% of phosphorus were provided by the nitrified urine. Depending on emissions related to urine fertilizer production, this may result in a reduction of overall production carbon footprint. Our study supports the feasibility of nitrified urine fertilizer utilization in commercial hydroponic tomato production, offering a sustainable and environmentally friendly approach to reduce the carbon footprint asso ciated with conventional mineral fertilizers.