The Impact of Foliar Biostimulants Derived from Animal Waste on Mitigating the Effects of Drought on Maize Crops in Southern Romania

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.