Early agricultural systems relied on recycling plant residues and composting to increase soil fertility. As the world demand for food increases, practices that lead to increased yields on existing farm lands will continue to be important. Humates are reported to increase crop yields, and reduce drought and high-temperature stress. Humic acid is soluble in dilute alkaline solutions, and is precipitated by acidification. Fulvic acid is the fraction that remains soluble after acidification, and cannot be precipitated.
Humins are insoluble in dilute acid or base.
Commercial humate products are either mined or extracted from naturally occurring sources. The humic acid contents of these deposits usually range from 30 percent to 60 percent. Humates can have beneficial effects on plant growth by stimulating the plant to absorb greater quantities of nutrients, and by inducing a more efficient use of the absorbed nutrients. However, these compounds have not been researched extensively. The objective of the field study was to determine if the use of humates as a fertilizer supplement increased yield or quality of turnips and mustard greens.