Abstract

Drought represents one of the major constraints limiting maize productivity in southeastern Europe, particularly under non-irrigated conditions. This study evaluated the effectiveness of foliar biostimulants derived from animal collagen and keratin hydrolysates in mitigating drought stress and improving maize performance in southern Romania during a six-year field experiment (2020–2025). During the screening phase (2020–2022), four formulations (FM1, FM2, KC, and K2) were applied at two rates (5 and 10 L ha−1) and compared with an untreated control. Significant effects of biostimulant formulation and dose were identified for plant height and grain yield (p < 0.001). Duncan’s multiple range test showed that K2 applied at 10 L ha−1 achieved the highest mean grain yield (87.71 q ha−1), significantly exceeding the untreated control (70.94 q ha−1). Based on these results, K2 was selected for long-term validation during 2023–2025 and subsequently evaluated across the entire six-year experimental period. Mean grain yield increased from 52.06 q ha−1 in the untreated control to 58.74 and 64.91 q ha−1 following K2 application at 5 and 10 L ha−1, respectively. Yield improvements were particularly pronounced during years characterized by severe precipitation deficits, when relative yield increases reached up to 41.9%. Economic analysis demonstrated positive net returns in all experimental years, with average profits of 108.6 EUR ha−1 and 206.9 EUR ha−1 for the 5 and 10 L ha−1 application rates, respectively. The results demonstrate that keratin-based biostimulants derived from industrial by-products can improve maize productivity, enhance drought resilience, and contribute to circular-economy approaches in sustainable agriculture.

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