Foliar application of humic acid at heading improves physiological and agronomic characteristics of durum wheat (Triticum durum L.)

Background: Crop production with lesser use of chemicals have attracted significant attention due to better quality. Organic manures are commonly used to fulfill the nutrient requirements of crop plants in organic farming. Humic acid could help to further improve the growth and productivity of crop plants in organic farming. Therefore, this study assessed the role of humic acid in improving physiological and agronomic attributes of durum wheat (Triticum durum L.). Methods: Five different doses of humic acid, i.e., 0 (H-0), 1.5 (H-1), 2.5 (H-2), 3.5 (H-3) and 4.5 (H-4) L/ha were applied at two different phenological stages, i.e., stem elongation (SE) and heading (H) of wheat in organic field. Durum wheat variety `Burgos' widely cultivated in Turkey was used as plant material. Data relating to chlorophyll index (CC), flag sheet area (FSA), proline content (PC), plant height (PH), protein ratio (PR), and grain yield (GY) were recorded. Results: Different physiological and agronomic traits were significantly affected by humic acid doses and growth stages. Overall, the lowest values of CC, FSA, PC, PH and GY were noted for H-0, whereas H-4 resulted in the highest values of these traits. Grain yield was 3882.82 kg ha (1) in H-0 and increased to 4988.14 kg ha(1) (28 %) in H-4 dose of humic acid. The GY was decreased, whereas PC and PR increased in the second year of the experiment due to warmer and drier weather conditions. The highest PC values were noted in H-0, and the PC values decreased with the increase in humic acid doses. Conclusion: Humic acid application created favorable growing environments for plant growth. Overall, the application of H-4 dose at heading stage resulted in the highest yield and related traits. Therefore, it is recommended that application of 4.5 L/ha humic acid at heading stage could be used to improve durum wheat yield under organic farming. (c) 2022 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.