Kelp meal is a natural soil amendment derived from dried and ground seaweeds, primarily the brown algae species known as kelp. The product is typically sourced from cold ocean waters, with the species Ascophyllum nodosum being one of the most common varieties used in commercial preparation.
Creation Process and Nutrient Profile
Following sustainable harvesting, the raw kelp is washed and then dried, often at low temperatures, to preserve its biological compounds. Once dried, the kelp is milled into a fine powder or a granular material, which is the final product.
While the nitrogen, phosphorus, and potassium (N-P-K) ratio is relatively low, often around 1-0-2 or 2-0-4, kelp meal is densely packed with over 60 different trace minerals. These micronutrients include elements such as iodine, magnesium, calcium, zinc, iron, and boron, which are necessary for plant function.
Kelp meal naturally contains plant growth regulators (PGRs). These organic compounds include auxins, cytokinins, and gibberellins, which are not commonly found in traditional mineral fertilizers. The composition is further enhanced by complex carbohydrates like alginates and mannitol, as well as various amino acids.
Benefits for Soil Structure and Plant Growth
The complex carbohydrates in kelp meal, such as alginates, function as natural soil conditioners when they decompose. They bind fine soil particles together to create better structure. This improvement enhances the soil’s capacity for water retention and promotes better aeration, which supports root respiration.
The presence of PGRs directly influences plant development. Auxins stimulate the proliferation of fine root hairs, establishing a more extensive root system for absorbing water and nutrients. Cytokinins promote vigorous cell division and delay senescence, helping to maintain healthier, more active foliage.
Kelp meal provides a gentle, sustained feeding regimen because its nutrients are released slowly as the organic matter breaks down over four to six months. This contributes to steady, balanced growth and helps prevent the rapid nutrient surges common with synthetic products. The compounds, including stress-response factors like betaines, also help plants manage environmental pressures, such as temperature extremes and transplant shock.
Guidelines for Garden Application
For new garden beds or container plantings, the meal should be mixed directly into the soil before planting to establish a long-term nutrient base. A standard guideline for general garden use is to broadcast approximately one to two pounds of kelp meal per 100 square feet of area, working it into the top few inches of the soil.
For container gardening, blend about one tablespoon of the meal for every gallon of potting soil.
Existing plants benefit from a top dressing: sprinkle a quarter cup around the base and gently work it into the surface soil near the drip line. Since the nutrients release over months, an application in early spring and another mid-season or in the fall is sufficient.