Assaying the Use of a Leonardite-Suspension Concentrate-Based Product as a Potential Biostimulant to Enhance Growth, NPK Use Efficiency, and Antioxidant Capacity in Lactuca sativa L. Atero Calvo, Santiago Magro, Francesco Masetti, Giacomo Navarro León, Eloy Ríos Ruiz, Juan José Ruiz Sáez, Juan Manuel Antioxidant compounds Crop yield Humic substances Biostimulants are presented as a potential tool to achieve the main objectives of modern agriculture: increase crop yield and nutritional quality while reducing chemical fertilizer use. Here, we investigated the use of a HS-based product (BLACKJAK®, from Sofbey S.A., Mendrisio, Switzerland) as a biostimulant to enhance plant growth, nitrogen (N), phosphorus (P), and potassium (K) use efficiency, as well as antioxidant capacity. For this purpose, BLACKJAK® was applied to lettuce (Lactuca sativa L.) as radicular (‘R’) and foliar (‘F’) at doses: 0.20 mL/L (R1), 0.40 mL/L (R2), 0.60 mL/L (R3), and 0.80 mL/L (R4), 5.00 mL/L (F1), 7.50 mL/L (F2), 10.00 mL/L (F3), and 12.50 mL/L (F4), along with a control. Shoot fresh weight (FW) and dry weight (DW), leaf area, NPK use efficiency parameters, and antioxidant capacity were evaluated. Our results showed that R1, R2, R3, F2, and F3 enhanced shoot FW and leaf area, while only R3 increased shoot DW. Furthermore, in general, most of the doses employed enhanced NPK use efficiency parameters such as apparent crop recovery, nutrient export, physiological efficiency, and internal utilization of applied nutrients. Similarly, HS also increased ascorbate, glutathione, and phenol concentrations, showing an improvement in antioxidant capacity measured through FRAP (Ferric Reducing Antioxidant Power) and TEAC (Trolox Equivalent Antioxidant Capacity) assays. Overall, root-HS offered better results than foliar-HS, especially at R3. Hence, our results indicate that BLACKJAK® could be a good candidate to enhance crop productivity and nutritional quality while reducing the use of chemical NPK fertilizers. 2024-04-16T10:26:02Z 2024-04-16T10:26:02Z 2023-12-26 journal article Atero-Calvo, S.; Magro, F.; Masetti, G.; Navarro-León, E.; Rios, J.J.; Ruiz, J.M. Assaying the Use of a Leonardite-Suspension Concentrate-Based Product as a Potential Biostimulant to Enhance Growth, NPK Use Efficiency, and Antioxidant Capacity in Lactuca sativa L. Agronomy 2024, 14, 64. https://doi.org/10.3390/agronomy14010064 https://hdl.handle.net/10481/90779 10.3390/agronomy14010064 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional MDPI