Vegetative Growth and Chemical Contents of Avocado (Persea americana Mill.) Saplings as Affected by Foliar Spray with Humic Acid and Seaweed Extract in Iraq

Avocado is a tropical fruit that has been recently introduced and acclimatized to Iraqi environmental conditions. The importance of this research lies in determining the optimal growth and production requirements for the plant in this new environment. Therefore, this study was conducted during the 2022 growing season to evaluate the effect individual and combined foliar spray with humic acid and seaweed extract on Avocado sapling growth and chemical properties. The experiment was factorial RCBD included humic acid at 0, 3, and 5 ml·L-1) and seaweed extract at 0, 2, 4, and 6 ml·L-1, with three replicates. The results showed foliar humic acid at 5 ml/L-1 significantly increased most vegetative growth characteristics, while a much higher increase resulted where applying seaweed extract at 6 ml/L-1. Overall, the highest increase values over the control were recorded in the interaction treatment 5 ml/L-1 humic acid and 6 ml/L-1 seaweed extract where ​sapling height, stem diameter, number of branches, number of leaves, and leaf area increased by 20%, 9%, 8%, 8%, and 20% over the control respectively. The same combination treatment showed also clear positive effect on leaf content of carbohydrate and macronutrients (NPK and Ca). The foliar spray with humic acid and seaweed extract, particularly in combination treatment, is effective in promoting avocado saplings growth and nutritional status under environmental conditions in Iraq.