Evaluating digestate-based fertigation strategies for sustainable forage maize production

The Atlantic Arc, traditionally marked by a temperate oceanic climate with regular rainfall, is now experiencing reduced and irregular precipitation along with longer summer droughts due to global warming. These shifts pose a growing threat to forage maize ( Zea mays L.) production during periods of peak water demand. In this context, the liquid fraction of digestate, a nutrient‑rich aqueous by‑product of the anaerobic digestion of cattle excreta, emerges as a potential alternative to potable water for irrigation, although its role in mitigating water stress remains underexplored. This pilot‑scale study assesses the effects of two liquid digestate‑based drip fertigation regimes (moderate or full supply) on forage maize yield and nutritional value during the critical summer period (July-August) over two consecutive agronomic years. Plant weight and crude protein content were significantly higher under the full-supply regime, while no significant differences were detected for the remaining variables. Nevertheless, productivity, plant height, energy and starch contents, and crop water productivity tended to show higher values under the moderate‑supply regime, suggesting potential agronomic benefits that merit further investigation under commercial-scale conditions. Soil analyses showed no detrimental changes in physico‑chemical properties, aside from an expected increase in potassium content and pH associated with liquid digestate application. Overall, the results suggest that both fertigation strategies could represent an advantageous balance between crop performance, resource use, and soil sustainability, with additional research required to enable the effective incorporation of these practices into circular agricultural systems.