Abstract
Leonardite and humic acid have been reported to improve plant growth by many investigators in very controlled settings. The objectives of this study were twofold. First, to determine if the use of leonardite as a fertilizer supplement improved crop growth and if there was a residual effect from previous applications. Second, to determine the effectiveness of humic acid as a seed treatment and priming agent. Three planting series were established using five treatments of 0, 56.1, 112. 1, 224.3, 445.6 kg leonardite per hectare. Subplots were treated at the first, the first and second, or all three planting series. Brassica rapa 'Purple Top White Globe' and Brassica hirta'Florida Broadleaf were used as the indicator crops. No differences in plant growth were observed between planting series or treatment rate. Difference in soil potassium and iron were observed however. A commercial liquid humic acid (Grow-Plexl P 15) solution and a technical grade humicacid were used. to test seed germination. Seeds of Capsicumannum 'Vera Cruz' and' Jupiter' were primed in one of the humic acids and/or NaCl. Significant differences found could not be attributed to the use of either humic acid source.
Duval, John Robert (1996). Plant response to leonardite and humic acid. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -D88.