Recent research published in the Environment Sciences & Technology by Prof. Naftali Lazarovitch and Dr. Ilya Gelfand researchers from the French Associates Institute for Agriculture and Biotechnology of Drylands of BGU compared the efficiency of fertilizer use and the environmental impact of integrated aquaculture-agriculture systems with different fertigation (fertilization + irrigation) configurations. Systems incorporating fish and vegetable production have been shown to have high water and nutrient use efficiency, however, the environmental impact and greenhouse gas emissions (GHG) of such systems weren't described yet. Studied systems differed by types of fertigation; the researchers compared fertigation by aquaculture effluent with and without ammonia addition and the common fertigation practice.
While the efficiency of fertilizer use, the yield, and the amount of nitrate leaching of the different systems were very similar, the emissions of nitrous oxide (N2O) and the N2O production pathways differed significantly between the systems. Recycling of nitrogen due to fertigation with aquaculture effluent prevented 32-37 kg of CO2 equivalent emissions per Mg of fresh cucumbers produced in comparison to the common fertigation practice.
Nitrous oxide emissions come third in terms of contribution to anthropogenic atmosphere warming, after methane (CH4) and carbon dioxide (CO2). More than 60% of N2O emitted globally is linked to agriculture and food production. Extensive research has been done on the effect of the type of nitrogen fertilizer, climate, soil type, crop type, irrigation, and more on the N2O emissions. The study by BGU researchers added to this research by describing N2O emissions from aquaculture-agriculture integrated systems, a promising setup for increasing food production in areas with water shortage. The study found that N2O emissions from the integrated system sharply increased after each irrigation event and more so when a readily available source of carbon was present. Overall, the rapidly changing emissions dynamics pointed out the importance of the timing of the measurements and led to the development of a model describing the decline of emissions with time.
The quick change in emissions (up to an order of magnitude in 1 hour) makes the timing of the measurement of N2O emission in relation to the fertigation event very important in translating that value to a seasonal emission. The effect of readily available carbon on the N2O emission should be taken into consideration when studying the emissions from integrated agriculture systems.