Humic and Fulvic Acid in Cannabis Gardening

Organic matter is essential to creating a healthy growth medium; humic and fulvic acid are two important components for vibrant plants.

Humic and fulvic acid, generally formed via secondary synthesis actions, are essential to healthy plant development. The two related substances work to increase a plant's nutrient uptake and help to condition the soil, leading to a more efficient use of applied fertilizers and extending the life of your growth medium. If used properly in a balanced garden, either biological (grown in soil) or soil-less, humic and fulvic acid can lead to healthier and more extensive root systems, increased yield and more vibrant plant growth and development.

What is humic acid (HA)?

Humic acid is organic matter that is dark brown to black in color, which is water-soluble at more alkaline levels (pH >2). An organic catalyst, HA is derived from the organic components of soil, including humus or peat. HA is actually a by-product of the micro-herd that is responsible for breaking down dead organic matter; many different organic acids are formed when organic matter biodegrades, and humic acid is an intricate mixture of such acids. This conglomeration includes "complex aromatic macromolecules with amino acids, amino sugars, peptides [and] aliphatic compounds involved in linkages between the aromatic groups." [Source]

An excellent soil conditioner due to its high molecular weight, humic acid is perfect for both soil and soil-less substrates, with regards to either supplementation or rejuvenation. The quality and efficacy of either dirt or soil-less media can be greatly increased by improving water retention and facilitating the movement of nutrients between soil particles, increasing the availability and even distribution of fertilizer.

A fantastic chelating agent, HA attaches itself to micronutrients, forming a composite that is more efficiently and easily absorbed by plants, promoting extremely high ion-exchange and buffering capabilities. Metallic elements such as magnesium, zinc, manganese, calcium and iron are absorbed more easily upon the application of humic acid, leading to an increase in both plant matter and root mass, including the formation of lateral or horizontal roots. This is true in biological (soil), hydroponic and aeroponic gardens.

What is fulvic acid (FA)?

Fulvic acid is a water-soluble humic material of a light yellow to golden to yellow-brown color that carries a very low (acidic) pH but is soluble in all pH conditions. With a lower molecular weight than humic acid, fulvic acid contains a higher oxygen content but lower carbon than the high-molecular weight humic acid. Due to the low molecular weight of FA, the substance easily penetrates the leaves of the plant, even entering its mitochondria. It is able to easily pass through cell membranes, which aids in nutrient absorption. For this reason, fulvic acid is extremely efficient when applied as a foliar spray or root drench.

Some gardeners balance the acidity of fulvic acid with more alkaline or basic supplements; for example, certain kelp products are processed with potassium hydroxide (caustic potash or KOH), which will help to swing the pH towards more desirable levels.

How are humic and fulvic acid beneficial to Cannabis plants?

Humic substances can be applied in a wide array of cultivation techniques, ranging from soil to soil-less settings, for clones and cuttings, as a soil re-conditioner to irrigation or dry, broad-cast methods of farming.

Both HA and FA chelate useful minerals into usable forms, increasing the availability and absorption of such substances. Toxins are caught up by the two, meaning that they are less of a threat to plants. In addition, water infiltration and holding capacity of the soil is increased, as is drought tolerance. This helps to decrease environmental stress, aids in seed germination, encourages root growth and respiration, increases cell membrane permeability and stimulates plant metabolism, enzymes and cell division.

Humic and fulvic acid are typically used to build quality substrates, applied in combination with microbial inoculants and organic fertilizers. The goal is generally to increase the organic matter in soil as well as its workability.

How to apply humic substances

Soil: Generally, either dry or liquid humic acid is diluted with water and fed directly to the soil. This is typically done when planting clones or established seedlings or just prior to germination, in the case of large Cannabis plots where seeds are sown.

Compost tea: Small amounts of dry HA powder or liquid concentrates are added to the bucket at the start of the brewing process.

Foliar spray: Either dry HA powder or liquid concentrates are diluted with water, then sprayed liberally or lightly onto plant leaves, according to the manufacturer's directions.

NOTE: Leonardite is not synonymous with all humic substances

True Leonardite originates from the hilly regions of the Dakotas and was named in honor of its discoverer, Dr. Leonard. While this substance is high in humic acid, it presents a minimal fulvic acid content, meaning that it is not optimal as an organic soil conditioner. The most effective humic additives contain a higher amount of both humic and fulvic acid.

An industry standard for procedural analysis of humic acid is difficult to source; various forms of the substance are available in a wide range of concentrations and price points. In order to avoid confusion, many gardeners purchase HA and FA products from local garden centers or online shops. This may also prevent overdosing or wasting money on unnecessary supplements. It is generally a good idea to follow the manufacturer's dosage instructions and the plants will benefit from small, regular applications of humic substances throughout the life of the crop, rather than in large, sporadic doses. Certain dry applications can be highly-concentrated and may contain solids that should be filtered out before attempting to pass the solution through small spray nozzles.