Agro-environmental profile of potato cultivation under water and nitrogen managements – A case study in Denmark

Potato field management in Europe is already optimized for high production and tuber quality; however, numerous environmental challenges remain if the industry is to achieve “green economy” targets, such as less resources utilized, and less nitrate leached to the environment. Strategic co-scheduling irrigation and nitrogen (N) fertilization might increase resource use efficiency while minimizing reactive losses such as nitrate leaching. This study aimed to quantify the combined effect of irrigation and N fertilization on potato production, growth, and resource use efficiencies. A field experiment was conducted from 2017 to 2019 on a coarse sandy soil in Denmark, with a drought event occurring in 2018. Full (I_full, maximized), deficit (I_def, 70–80 % of I_full) and low irrigation treatments (I_low, minimized amount to keep crop survival), each under full (N_full, maximized) and variable (N_var, variable amount according to the crops’ needs) N fertilization were applied. The analyses results show that I_low limited potato growth under a drought-heat event; otherwise, potato growth was comparable between I_full and I_def treatments, with 31–32 % higher irrigation efficiency (IE) under I_def than under I_full. Nitrate leaching was variable and not significantly different among the treatments, being in general 9–13 % lower under I_def in absolute terms than under I_full. Unexpectedly, outcomes from N_var were statistically lower compared to those from N_full. Radiation use efficiencies (RUEs) from I_low and N_var were significantly lower than from I_full and I_def (14–19 %), and from N_full (9–11 %). N use efficiencies (NUE) were comparable between N fertilization treatments but significantly different among different irrigation treatments. Overall, this study confirms that I_def is the best irrigation strategy. Future efforts should focus on developing improved approaches for detecting in-season crop N status and further quantifying N requirements, as well as promoting the co-scheduled management of irrigation and N fertilization. Remote sensing approaches have great potential to assist with this.