Kelp Meal Vs. Fish Emulsion

While some gardeners lug home bags of artificial 10-10-10 without giving much thought to their contents, organic growers struggle to figure out what those numbers mean -- and how to obtain earth-friendly equivalents. Plants need the "big three" elements reflected in those bags of 10-10-10 or 10-20-5, which stand for nitrogen, phosphorus and potassium, respectively. Fish emulsion and kelp meal are each useful organic fertilizers. But while they both come from the sea, the nutrients they provide and their application methods are very different.

Kelp Meal

Created from nutrient-rich seaweed, kelp meal is a dried, ground fertilizer product. Organic gardeners use it primarily as source of potassium, but it does contain other nutrients. The nutrients exist at a 1.0-.05-2.5 ratio of nitrogen, phosphorus and potassium, respectively. Adequate amounts of potassium in the soil help plants resist disease and develop strong stems. Kelp meal also contains 60 trace elements aside from the "big three" of nitrogen, phosphorus and potassium, notes Rodale's "Ultimate Encyclopedia of Organic Gardening." The Rodale volume suggests using kelp meal as both a potassium source and as a growth enhancer. Organic growth enhancers appear to stimulate the enzymes in plants which signal them to start growing.

Fish Emulsion

Fish emulsion is a liquid organic fertilizer which primarily provides nitrogen. Its ratio of nutrients of N-P-K is 5-2-2. Nitrogen promotes healthy, green foliage and overall growth. Fish emulsion is also a good source of sulfur, which encourages strong systems and helps plants convert sunlight into fuel. While it's possible to use the liquid fertilizer for soil building, most gardeners reserve it for feeding plants directly.

Kelp Meal Application

For every 100 square feet of garden bed you plan to fertilize, broadcast 1 to 2 lbs. kelp meal over the soil in the spring, along with other dry nutrients, and till them into the top 4 inches of your garden bed. Once the plants are established, they may benefit from a mid-season application of kelp meal, which you may provide by placing in 1-inch-thick layers along crop rows or in circles around individual plants.

Fish Emulsion Application

To add nitrogen to 100 square feet of garden soil, add 1/10 oz. liquid fish emulsion which has been diluted in the amount of water recommended on the label. Gardeners more commonly use liquid fish emulsion to feed plants directly by diluting the fish emulsion at recommended rates and gently pouring the liquid on the leaves and the soil directly under their stems.

Alternatives

As with cooking the perfect chili, the subject of which ingredients create the healthiest soil remains subject to debate. The Rodale volume considers kelp meal ideal for both adding phosphorus and as a growth stimulator, while Colorado State University Extension considers its nutrient level "negligible." If you don't have access to kelp meal or are concerned about its value, consider using potassium-rich ground rock powders like greensand or granite meal instead. To replace liquid fish emulsion, till a solid nitrogen source like manure, blood meal, cottonseed meal, fish meal or soybean meal into the soil before planting, and place 1-inch-thick circles of any of these fertilizers around plants once or twice during the growing season. Alternatively, foliar-feed plants with homemade high-nitrogen "teas" created by soaking manure or compost in water and straining the resulting liquid.