Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: October 9, 2012
Publication Date: February 4, 2013
Citation: Olk, D.C., Dinnes, D.L., Callaway, C., Raske, M. 2013. On-farm evaluation of a humic product in Iowa (U.S.) maize production. In: Xu, J., Wu, J., and He, editors. Functions of natural organic matter in a changing environment. Dordrecht, The Netherlands: Springer. p. 1047-1050. Technical Abstract: The benefit to corn (Zea mays L.) production of a humic product derived from lignite was evaluated for three years under otherwise conventional crop management in Iowa farmers’ fields. It was applied at a rate of 3.57 L ha-1, generally as a foliar spray mixed into routine pesticide applications during early stages of crop growth. In each of three years, hand-sampled corn plants collected at physiological maturity in 30 to 35 farmers’ fields across Iowa showed a significant increase in grain weight with product application in 70 to 80% of the cases, covering a range of soil types and grain yield levels. Mean increases were 630-940 kg ha-1. A limited number of yield increases estimated by mechanical combine were typically 310-630 kg ha-1, or about 5% of normal yield levels. Grain weight increases were associated with longer, thicker, and heavier cobs and slightly larger stover biomass. Plant nutrient concentrations were not affected at harvest. In-season measurements in a few intensively monitored farmers’ fields associated product application with slightly taller plants, increased leaf area, earlier onset of pollination, extended grain filling, and delayed senescence, i.e., extended duration of photosynthesis and decayed rotting of stems. Limited visual observations indicated great proliferation of roots, especially lateral roots. Ongoing data assessment will identify any environmental factors of product efficacy, an issue that to date remains unexplored in the humic product literature. Initial studies of alfalfa (Medicago sativa L.) found biomass increases with product application of 7 to 29%. The humic product increased economic yield in a large majority of cases by amounts that were agronomically modest but economically significant.