Neptune’s Harvest Crab Shell provides NPK, calcium and magnesium. It can help with nematode and fungus problems, as well as ants and grubs.
Photo courtesy of Neptune’s Harvest .

What’s new in fertilizers and compost? In synthetic fertilizers, nothing comes close to the changes that occurred after World War II, when unused war materials were first used to manufacture the dry nitrogen, phosphorus and potassium that replaced manures, eventually becoming the world’s fertilizer of choice. In more recent times, perhaps the past 15 years or so, manufacturers have added various micronutrient packages (an assortment of blends of iron, chlorine, copper, manganese, zinc, molybdenum, boron and others) to that basic mix. “Most recently, manufacturers are working to develop ways to slow the release of nitrogen so that less sits on the surface and more will be available to plants as roots grow,” says Carl Majewski, field specialist, food and agriculture, University of New Hampshire Cooperative Extension.

Slow-release fertilizers are treated or coated with various substances that reduce the solubility of the encapsulated nutrients. Temperature, moisture, and the type and thickness of the coating determine the rate at which nutrients are released. “While these materials do have an effect on how quickly the fertilizer is available, there isn’t a lot of unbiased research showing how well the rate of nutrient release matches up with crop uptake,” says Majewski. Because of the cost of slow-release fertilizers, he suggests that growers look for good independent data on their reliability before purchasing them.

Researchers, manufacturers and growers are currently working to more accurately determine when and in what amounts fertilizer should be applied. They are finding that soil and plants require less fertilizer than had previously been thought necessary. Corn, for instance, may not require a concentrated source of phosphorus provided by a starter fertilizer. While there are instances where starter fertilizer does provide a response (in cold, wet soils for example), research going back several years shows that corn planted in well-drained soils that are already high in soil test phosphorus do just fine without it, according to Majewski.

“Keep up with soil testing,” says Majewski. “That is the best way to determine the amount of fertilizer to apply.”

Soil health is also a more recent area of interest. The biological profile, microorganisms and active carbon in soil all affect how that soil is managed – which materials are added to soil (carbon and beneficial microbes, for example), in what form it is added (synthetic or organic), and how crops are rotated.

“Even if you were to start with similar composts or fertilizers, you wouldn’t be able to tell which will be best in any given plot,” says Majewski. “At this point in our understanding, we can’t say any one material is better than any other. Any compost will add materials and help condition soil. Exactly how much will do what is not known and may remain a question.”

Plant food

Fertilizers are intended to feed plants, providing them with the elements they need for growth. In synthetic fertilizers, recent changes are relatively small and are primarily in the formulation of micronutrient blend packs and in coatings to slow the rate of release of nutrients. Organic fertilizers come from a number of sources; for example, one company now offers a crab shell product, and another utilizes chicken litter.

Piles of McEnroe Organic Farm’s products ready for use.
Photo court esy of McEnroe Organic Farm.

Ocean Crest Seafoods is a longtime processor of fresh fish and shellfish based in Gloucester, Mass. The company initially developed Neptune’s Harvest fish-based fertilizers to utilize the byproducts of the fish filleting process – fish heads, skeletons, scales and fins – that had previously been dumped into the sea.

Over the years, the company’s product lineup has grown to include hydrolyzed fish fertilizer, a fish-seaweed blend, liquid seaweed fertilizer concentrate, kelp meal and, most recently, crab shell. A dry organic source of NPK (2.5-3-0.5), Crab Shell also contains 23 percent calcium and 1.33 percent magnesium. Crab Shell is high in chitin, a nitrogen-containing polysaccharide that serves as an armor or cell wall for fungi and arthropods, including all crustaceans and insects. When added to soil, chitin promotes the growth of chitin-eating bacteria, which in turn helps create a hostile soil environment for fungus, grubs, ants and nematodes.

Crab Shell helps retain moisture in the soil, build organic matter and control slugs. The edges of the crab shell particles, which range from the size of a grain of sand to the size of a pinky fingernail, are sharp and cut slugs. As a source of calcium, Crab Shell helps prevent blossom-end rot and powdery mildew.

“Crab Shell is great as an additive to compost and potting soil,” says Ann Molloy, director of sales and marketing for Neptune’s Harvest. The company advises applying Crab Shell once a year at the rate of 100 pounds per acre. Crab Shell is available in 4 and 50-pound bags, 12-pound pails or by the ton.

The high-nitrogen dried poultry fertilizer made from hen litter at Herbruck’s Poultry Ranch is, according to the company’s website, in demand as an alternative to synthetic fertilizers for growing grain. An analysis of Herbruck’s Pelletized Poultry Fertilizer can be found at

Low-odor pellets are spreadable using dry fertilizer equipment. Pellets are sold by the ton and are “suitable for organic farming.”

Tomatoes grown using McEnroe Organic Farm products.
Photo court esy of McEnroe Organic Farm.

Improving soil

While fertilizers feed plants, compost feeds the soil. Compost improves soil structure, helps retain moisture, supplies organic matter and beneficial microorganisms, and provides other benefits. Like fertilizer, compost can also be derived from a variety of sources.

Millions of earthworms in an all-organic system convert organic material from a family dairy farm to the soil fertility products developed by Worm Power. The organic materials are first processed by heat to ensure that Worm Power is free of weed seeds and pathogens, and then they’re organically processed by several classes of microorganisms and over 8 million earthworms.

A 4-pound bag of Neptune’s Harvest Crab Shell.
Photo court esy of Neptune’s Harvest .

“Vermicomposts are beneficial to the physical, chemical and biological properties of soil and to the plants that grow on them,” says Dan Johnson of Worm Power.

Available since 2005, Worm Power is odorless and safe for people and pets. It is listed by the Organic Materials Review Institute (OMRI) under worm castings and can be purchased from distributors throughout the northeastern and central states and scattered locations in the West.

“The trend toward eating local continues to increase our market for high-quality food and the materials to grow it,” says Erich McEnroe of McEnroe Organic Farm, a 1,200-acre sustainable operation in Millerton, N.Y. McEnroe cites this trend as a major driver in the expansion of his family’s business, which includes 60 acres of vegetables, 17 greenhouses, 150 certified organic beef cattle, lambs, poultry, pigs, and the compost and potting soils made, in part, from the farm’s waste. McEnroe Farm’s compost-based Premium Organic Potting Soil and Premium Lite Growing Mix are listed by OMRI. These products are available in 22-quart bags, 0.05-cubic-yard bags, 1-cubic-yard sling bags and in bulk.

Pasteurized mushroom substrate (mushroom compost) is available to growers of other crops in parts of the country where mushrooms are grown commercially. Mushroom compost may contain wheat straw, straw-bedded horse manure, hay, poultry manure, cottonseed hulls, cottonseed meal, cocoa shells, gypsum and sphagnum peat moss. A good source of humus, mushroom compost (1-0.5-1) tends to be slightly acidic, with a pH of around 6.5 to 7.

Hy-Tech Mushroom Compost, Inc. offers its product only in bulk shipments from West Grove, Pa. Although Hy-Tech Mushroom Compost is not certified organic, Lisa Van Houten, Hy-Tech’s marketing coordinator, suggests that organic growers who wish to use the product check with their state certifying organization about its use under the 120-day rule.

For years, growers at Vermont Compost Co. have added a blend (or suite) of three kinds of stones – ground granite, basalt and Champlain Valley calcium carbonate from ancient mollusk shells – to the firm’s standard Compost Plus container and transplant booster mix. This is the first year the blend will be available for sale to the public.

McEnroe Organic Farm offers Premium Lite Growing Mix, Premium Organic Compost and Premium Organic Potting Soil.
Photo courtesy of McEnroe Organic Farm.

The heavy blend is 75 percent stone by weight (the remaining 25 percent is compost) and is useful in long-term soil remineralization efforts. As of this writing, Stone Sweet was not yet listed on the company’s website, but company founder Karl Hammer says that Stone Sweet is available by emailing All of Vermont Compost’s products are suitable for organic growing.

There are many options on the market when it comes to fertilizers and compost. When choosing products, Majewski suggests bearing in mind that how soil is managed – cover crops, tillage, crop rotation – is as important as what is added to it. l

Kathleen Hatt is a freelance writer and a frequent contributor to Growing. She resides in Henniker, N.H.