Agronomic evaluation of leonardite on yield and chemical composition of canola and wheat
Dilk, Sean B.
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Leonardite is a naturally occurring material enriched in humic and other organic acids and is defined as oxidized lignite produced through the weathering of subbituminous coals and carbonaceous shales (Hoffman et al. 1993). In Canada, leonardite deposits have been discovered in Alberta and Saskatchewan. Leonardite has been shown to have variable effects on plant growth. Preliminary research trials by Akinremi (1999) showed that application of leonardite increased root growth of canola. In other trials, humic acid, derived from leonardite, improved the fresh and dry weight of tomato roots (Adani et al. 1998). The increase in root growth due to the aplication of leonardite suggests that the leonardite material may contain compounds that elicit hormone-like responses. O'Donnell (1972) discovered that leonardite contained polyphenolic compounds, some of which behaved similarly to auxin. The growth and dry matter production of crops have been enhanced with the addition of leonardite... Application of leonardite also affects the chemical composition of crop species. Nitrogen and P concentration of tomato and corn crops were elevated in the presence of leonardite (Adani et al. 1998, Lee and Bartlett 1976). The application of leonardite on a loamy sand increased the P concentration of corn plants (Duplessis and Mackenzie 1983). Micronutrient concentration of crops has also been enhanced with the application of leonardite. Iron (Fe) concentration in tomato was elevated with leonardite application (Adani et al. 1998) and lignite improved the concentration of Fe in mustard (DeKock 1960). Application of organic amendments, also containing humic acids, enhanced the Cu, Zn, Mn, and Fe concentrations of wheat seedlings (Moris 1985). Generally, the studies conducted to date showed highly variable effects of leonardite... The studies reported in this manuscript included several individual studies to examine the agronomic potential of leonardite and/or products made from leonardite. The objectives of this study were to: 1) the effect of leonardite on the yield and chemical composition of canola and wheat. 2) the effect of leonardite on the emergence of canola on poorly structured soils. 3) whether or not addition of humic acid to a P fertilizer band can improve P fertilizer use efficiency. 4) whether or not humic or fulvic acid can improve chelation and plant availability of Cu and Zn. 5) whether or not application of leonardite can reduce the concentration and accumulation of Cd in durum wheat. Literature pertaining to the five areas listed above was reviewed and discussed.