Reducing the environmental impact of maize by fertigation with digestate using pivot and drip systems

Reducing ammonia emissions is one of the great environmental challenges of the agricultural sector and is by far the most important emitter of this air pollutant. This study analyses maize cultivation with an emerging organic fertilisation management technique, i.e., pre-seeding injection, followed by side-dressing fertigation, through a life cycle assessment approach at the farm gate with the aim of evaluating its influence on crop production as a whole, with a focus on nitrogen emissions during field application. This was done on two sample farms, one of which was fertigated using drip irrigation and the other by pivot irrigation. Each farm was then compared with a reference scenario in which traditional organic fertilisation and irrigation were used. The inventory data consist of measurements made during field trials, data collected from questionnaires to farmers and modelling estimates. The optimised management of the digestate led to important reductions in the impacts affected by ammonia emissions; acidification was reduced by 68% and 80%. Relevant mitigations were achieved for eutrophication and particulate matter formation and for the carbon footprint (12–14%). A trade-off was identified in the increased impact on the consumption of fossil and mineral resources (13–17%) due to the construction and operation of a vibrating screen operating the filtration of the liquid fraction of digestate. In conclusion, the results indicate the general benefits of improved organic fertilisation management as a whole. Future efforts should be aimed at energy and construction efficiency measures of digestate treatments.