On-Farm Evaluation of a Humic Product in Iowa (US) Maize Production

Abstract

The benefit to corn (Zea mays L.) production of a humic product derived from lignite was evaluated for 3 years under otherwise conventional crop management in Iowa farmers’ fields. A liquid extract, 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 3 years, hand-sampled corn plants collected at physiological maturity in 30–35 farmers’ fields across Iowa showed a significant increase in grain weight with product application in 70–80% of the cases, covering a range of soil types and grain yield levels. Mean increases were 630–940 kg ha⁻¹, and these were inflated, as expected, compared to a limited number of yield increases estimated by mechanical combine, 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 7–29%. A newly begun corn trial on nitrogen fertilizer response will estimate the amount of N fertilizer input that can be replaced by humic product application to save input costs and mitigate environmental degradation. The humic product increased economic yield in a large majority of cases by amounts that were agronomically modest but economically significant. Future work will expand to soybean (Glycine max (L.) Merr.) production.