ARS | Publication request: PLANT GROWTH ENHANCEMENT BY HUMIC SUBSTANCES: EFFECT OF IRON

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 1999
Publication Date: N/A

Technical Abstract: Stimulatory effects of humic substances (HS) on plant growth have been observed and widely documented. Often these effects were attributed to plant growth hormones. An alternative hypothesis suggests that growth enhancement of plants grown in nutrient solution containing HS is the result of improved micronutrient availability; Fe in particular, has been postulated and tested in the present study. Plant growth experiments were carried out on both dicot (melon) and monocot plants (creeping bentgrass) due to the major difference in their Fe uptake mechanisms. The addition of humic acid (HA) or fulvic acid (FA) did not result in growth enhancement or a remedy of the Fe deficiency, suggesting that no plant growth hormones were present. However, addition of Fe, and either HA or FA resulted in healthy, chlorophyll-rich plants and enhanced growth, thereby proving that improved Fe availability is a major mechanism of plant growth stimulation by HS. A novel screening system for HS effects on plants grown in nutrient solutions was used. The feasibility and impact of HS utilization in horticulture will be presented.