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Organic Fertilizer List

Published in a Spring Home & Garden supplement to the Nashoba Publishing papers and the Fitchburg Sentinel, under the title "Organic Fertilizers are Just Part of the Mix" Appeared in the six Nashoba Publishing papers on 26 April 2001. This information has been expanded in the Soil section, but if you want a quick summary to print out, use this page.

If you’re interested in soil that’s healthy and full of earthworms, try organic fertilizers. Here are some to start with; there are lots of other possibilities.

For Phosphorus (the P in the NPK formulas):
Rock Phosphate: this is plain ground rock, not the “superphosphate” that is commonly available. Apply 2-10 pounds per 100 square feet.

For Potassium (the K in NPK formulas):
Greensand. Ground rock laid down originally as undersea deposits, this is also rich in trace nutrients. It helps compost piles cook faster, improves drainage in heavy soils, and improves water retention in sandy ones. (I know, that sounds contradictory, but it’s true!) Apply 5-80 pounds per 100 square feet.

For Nitrogen (the N):
Soybean meal is the best: it is the most economical source of nitrogen as well as the least polluted, since it is sold as livestock feed. It only comes in 50-pound bags, and you have to store it in a metal garbage can with a tight-fitting lid, because even in a plastic bin animals will chew right into the container to eat it. It’s 7% nitrogen (which the bag won’t tell you, as the ones sold for fertilizers do); apply 2-6 pounds per 100 square feet.

Other organic sources of nitrogen which are readily available and you can buy in smaller amounts: animal manures, cottonseed meal, blood meal (dried blood) and pelleted chicken manure. The chicken manure is the most organic; blood meal and fresh manures are the highest in nitrogen. Fresh manure should never be put directly on the garden when plants are growing; blood meal may be, but sparingly.

Trace nutrients:
Besides greensand, another good source of trace nutrients is liquid seaweed. This is particularly beneficial for any plant subjected to stress, such as seedlings you are setting out, transplants, and victims of drought or other damage. Liquid seaweed is not so easy to find as the other organics; your local health food store may be able to get it if the fertilizer sources can’t. Sometimes it’s sold combined with fish emulsion; the fish gives it a higher nitrogen content — but beware: cats smell the fish, and dig up the plants I put it on.

Mixing your own combination of N, P and K is the most economical way to use organic fertilizer, as well as the best way to meet specific conditions in the garden. Don’t worry about getting the formula just right; it’s not so important with organics, since (with the exception of blood meal) you're not likely to hurt your plants or your soil by using too much. If you don’t want to bother making your own, there are premixed organic formulas available in several brand names; the most common are probably Espoma and North Country Organics.

More important than what the lime adds to the soil is how it changes the pH; all the fertilizers you add are useless if the pH is too low or high because the nutrients get locked up in chemical forms the plants can’t take in. Use plain crushed dolomitic limestone and always test the pH of your soil with one of the easy test kits you can get at hardware, garden and farm supply stores.

This soil amendment — gardener’s gold — has many nutrients, but even more important is the organic matter it adds, which brings earthworms and promotes proper soil structure. Pricey to buy, it may be worth it until you get your own compost cooking.

Some sources in my area:
Townsend - Farmer’s Exchange (978) 597-2652
Fitchburg - United Cooperative Farmers (UCF)
Leominster - Farmer’s Exchange (978) 534-7698
Lancaster - Agway (978) 365-2194
Littleton - Agway (978) 486-9200
Milford (NH) - Blue Seal Feeds (603) 673-2601
Milford (NH) - Agway (603) 673-1669

© Copyright 2001 Catherine Holmes Clark