Impacts of Humic Product Application On Yields of Potato and Other Field Crops.

Commercial humic products are extracts from organic materials, including immature coals (lignite, leonardite) and composted plant residues. Their application to field crops has been claimed to promote increased crop growth and economic yield, although little published evidence exists.  In two independent research projects, our field data indicate the application of humic products led to improved economic yield, biomass, quality and nutrient content of potato in irrigated sandy soils of Egypt and increased biomass and economic yield of corn and alfalfa in Iowa, without requiring additional input of fertilizer or water. We will also discuss limitations in extrapolating from these results: we do not know the plant or soil processes through which humic products affect plant growth, and the manufacturing of humic products is not standardized.