Most of the soil organic matter is composed of humic substances (Nardi et al. 2002). Humic substances nurture plant cell membrane functions and encourage nutrient uptake. In the past ten years, there has been a growing body of evidence supporting the use of bio-stimulants in agriculture for both horticultural and field crop production systems, where they have been shown to increase root growth, enhanced nutrient uptake, and increase stress tolerance. du Jardin (2015) defined plant bio-stimulants in five categories: 1) microbial inoculants, 2) humic acids, 3) fulvic acids, 4) protein hydrolysates, and 5) amino acids, and seaweed extracts.
Fulvic acid, is of particular interest, as it is a natural chelator and thus helps facilitate migration of metal ions and nutrients across tissue membranes (Sun et al, 2012). It also retains many properties that make it ideal for foliar tank mixes, such as: (a) high solubility under different pH conditions (b) high cation exchange capacity, and (c) recorded absence of antagonistic effects with nutrients or pesticides. Owing to its low molecular weight (a few hundred Daltons), it can easily cross plant tissue membranes, and remains in solution even at high salt concentrations. All of which are considered ideal for foliar nutrient applications.
At the North Peace Applied Research Association, an experiment was designed to determine if foliar applications of Nitrogen with or without additions of fulvic acid have an effect on yield and leaf nitrogen content in canola, field pea and wheat. For field pea, only one treatment was conducted where foliar application of fulvic acid at 0.65 L ac-1 was applied at the 6th node and at the 12th node stage. This treatment was compared against a control where peas were sown in furrow with 13-33-0-15S at 120 lb ac-1. Above ground biomass was collected one week after foliar applications on each crop. For canola and wheat, the experiment was designed as a complete randomized block design with four treatments: (1) Dry urea at 150-175 lb ac-1 treated with fulvic acid at 0.3 L ac-1 applied at seeding, (2) Dry urea at seeding at 80-105 lb ac-1 followed by two foliar applications of liquid urea at 20 L ac-1, (3) Dry urea at 80-105 lb ac-1 treated with fulvic acid at 0.3 L ac-1 at seeding and two foliar applications of liquid urea with fulvic acid at 20 L ac-1 and 0.65 L ac-1, respectively and (4) seeding application of dry urea at 80-105 lb ac-1 treated with fulvic acid at 0.3 L ac-1 followed by two foliar applications of fulvic acid with a nitrogen, calcium and magnesium supplement (Nitro 18) at 0.65 L ac-1 and 20 L ac-1, respectively. In addition, a control treatment was included consisting of a sole application of dry urea at seeding at 150-175 lb ac-1.