Drip fertigation with slurry as a promising tool to reduce nitrogen losses under organic maize.

The European Union (EU) actively promotes the adoption of organic farming, in which crop N requirements are satisfied via organic fertilizers, such as slurry. Maize (Zea mays L.) is a key crop for both feed and food production with high N uptake. In this short-term study, we tested fertigation with microfiltered slurry liquid faction for maize fertilization as viable strategy to enhance nitrogen use efficiency (NUE) under organic farming while reducing N losses, via ammonia (NH), nitrous oxide (NO), and nitrate leaching (NO). We compared three strategies (i) slurry application through surface broadcast of the liquid fraction before sowing as reference fertilization ("Ante" treatment, or "A"), (ii) slurry application through both pre-sowing broadcast of the liquid fraction and fertigation as side-dressing with the microfiltered liquid fraction ("Ante + Post" treatment, or "A + P"), and (iii) slurry microfiltered liquid fraction application as side dressing via fertigation ("Post" treatment, or "P"). Compared to "A", cumulative N losses were reduced by 38% under "A + P" and 58% under "P". Furthermore, NH volatilization decreased by 43% and 71% under "A + P" and "P", respectively. These treatments also reduced NO emissions by 30% and 37%. Nitrate leaching was reduced by 56% in the "P" treatment. Overall, the "P" strategy was the most effective in reducing N losses, while "A + P" tended to increase grain production (12.6 Mg ha) and NUE (38.1 kg grain kg N supply) compared to "P" (11.0 Mg ha and 35.5 kg grain kg N supply). These results were primarily attributed to the improved synchronization between N supply and maize N requirements, emphasizing the risk associated with slurry application before sowing. Although conducted over a short experimental period, our study suggests that drip fertigation with slurries can overcome the potential yield losses of organic systems for crops with high N demand such as maize, while reducing N losses, fulfilling the environmental principles of organic farming and current requirements from EU policies.

© 2025. The Author(s).