SEAWEED EXTRACT AND HUMIC ACIDS BIOSTIMULANTS TO IMPROVE GROWTH AND POST-HARVEST QUALITY OF SPINACH AND LETTUCE
The leafy greens are highly perishable vegetables that are affected by pre-harvest and post-harvest conditions. Biostimulants can be utilized to enhance germination, growth, yield and quality of the crops. In this study, the effect of two plant biostimulants, Ascophyllum nodosum extract (ANE) and humic acid (HA) and their combinations (ANE+ HA) were evaluated for their potential to improve growth and minimize post-harvest losses in lettuce and spinach. Thirteen combinations of ANE and humic acids were assessed for seed germination and early growth of lettuce and spinach. Among these, most effective treatments were used to analyze postharvest quality of lettuce and spinach. In the laboratory, the application of ANE, HA, and ANE+HA significantly (p ≤ 0.05) improved germination and early growth parameters of lettuce and spinach. The combination treatment, 0.25 % ANE and 0.2 % HA (T12) showed 103.2% and 13.1% increase in the radicle length of lettuce and spinach, respectively. Similarly, plumule length was also higher in the presence of ANE, HA, and ANE+HA. Under the greenhouse conditions the weekly application the biostimulants improved biomass in all treatments but fresh and dry biomass in lettuce treated with 0.25 % ANE and 0.2 % HA (T12) were 103.1% and 113.9% respectively, compared with control. Whereas in spinach T12 had increased fresh and dry biomass by 62.9% and 103.3%, respectively. Pre-harvest treatment of lettuce and spinach with the combined ANE and HA significantly reduced fresh biomass loss during storage at 4⁰C for up to 21days. Further visual appearance quality (color, turgor and reduced softening of tissue) was also maintained while the nutritional quality of total antioxidants and phenolics were 1.7 and 1.5 folds, respectively, higher than the control. The preliminary results suggest ANE, HA and combination ANE + HA would enhance seed germination, plant growth and retain post-harvest quality of lettuce and spinach.