A Budget-Friendly Guide to Organic Fertilizer and Soil Amendments

In The Small Budget Gardener(Cool Springs Press, 2009), Maureen Gilmer offers down-to-earth, budget-friendly advice, ideas and resources to help you squeeze the most from your garden. In this excerpt from Chapter 3, “Free Dirt,” Gilmer explores inexpensive choices for organic fertilizer and soil amendments, from animal manure to agricultural and forest byproducts, and where to find them.

Green Choices for Organic Fertilizer

We don’t live in a perfect world, but there’s huge pressure to become a “perfect” organic gardener. We try hard to follow all the rules, but the reality is that budget and time constraints limit our choices. Gardening itself is important no matter how you do it, and successful yields is the real goal, not necessarily the process. So if you have to break a few rules now and then, don’t feel you’ve committed a mortal sin. Keep the perfect organic gardening model as your ideal and strive to follow it knowing that nothing is perfect and neither are gardeners.

What makes traditional gardening different from the organic approach is the use of synthetic fertilizers. These are rated by the three numbers on the label, which indicate the percentages of nitrogen, phosphorus, and potassium (NPK) in the formula. For example, a common granular all-purpose product is 16-16-16. Compare that to cow manure, which is about 2-5-2.

The numbers don’t tell the whole story, though. When you look at the organic materials in the charts that follow, remember that they do more than just add nutrients, they contain all sorts of smaller minerals, microorganisms, and soil conditioning abilities.

These charts are prepared to illustrate the vast potency differences so the new organic gardener discovers where the nutrients lie. It also helps if you compare your sources and their potency for the best value per dollar you spend. Fortunately, many are free, which is one of the beautiful things about organic gardening.

Top Three Synthetic Garden Fertilizers and Their NPK Analysis

Miracle Gro® 24-8-16
Spectrum 15-30-15
Shultz 10-5-10

Manure Content Comparison

These manures are better fertilizers, and due to the amount of undigested fiber in some of them, they also make fine soil conditioners.

Sometimes you’ll find manures mixed into bulk materials such as straw or shavings. This is often termed “bedding” and can include manure from a number of animals. Note how low the content numbers are for the bulk materials list compared to that of the manures. Bedding itself can drag down an overall fertility rating. When evaluating bedding, note the amount of actual manure present. If the bedding is composed of shavings, which contain no nitrogen, and it is combined with a little horse manure that is only 0.7 percent nitrogen, you’re getting no boost whatsoever. In fact, due to a complex process by which soil breaks down woody matter, your soil can actually end up less fertile than when you started. This is why knowing the nutrient content really matters.

Bulk Materials

These materials make better mulches or soil amendments and may benefit from being used with a supplemental nitrogen source.

Anyone can go out and buy manures or compost by the bag from a home improvement store, but using them to treat a sizable area becomes expensive. For many types of organic matter such as manures, obtaining it in bulk is the most economical way to amend a sizeable garden.

To amend raised beds, try using buckets, such as the ones cat litter comes in, to transport materials. Another method is to use heavy-duty plastic garbage bags. Fill them only one-third full or less to prevent tearing, then pack them into the trunk of your car or haul them. If you don’t own a pickup truck or can’t find one to borrow, try renting a little trailer to haul behind your car. Beware of hauling right after it’s rained because these materials, if they have been stored outdoors, can become considerably heavier to load and haul. This is why many experienced gardeners haul their soil materials in the dry, fall months to stockpile until they are ready to till it in spring.

The Manure Safari

In some cases, the only way to buy manure is by the bag, so start keeping your eyes open for sales where the prices on cow manure may drop for a short time. That’s the best time to stock up whether you need it right away or not. Bagged poultry manure, along with some other animal waste, rarely contains bedding materials. It may be composted and sterilized, which means it is free of weed seeds and not likely to “burn” plants. But again, this costs money.

The concept of a manure safari is to scope out inexpensive or free sources of bulk manures in your area. Remember that, to most people, manure is waste product that they must get rid of, and they are usually thankful that you are willing to pick it up. This stuff won’t be composted or sterilized, but that’s never stopped old-fashioned gardeners from growing massive crops.

Dairies and Stockyards: Dairies and stockyards offer the best source of manure with minimal weed seeds. Cows have three stomachs, which means they digest more weed seeds than other livestock. (They do not digest all, however.) A dairy or stockyard is the best place to obtain large quantities that can turn a backyard kitchen garden into a really fabulous producer in a single season.

Farms: Farms are often rich in all sorts of manures. You may be able to clean out a chicken coop in exchange for some buckets of free, high-powered organic “fuel.” Poultry manure has the richest amount of nitrogen of all livestock manures, and a small amount goes a long way.

Ranches: The environmental impact of manure runoff makes it mandatory for ranchers to strictly control accumulations, so you may be doing them a favor by carting it away.

Horse Stables: The equestrian set loathes flies, which are drawn to manures, and will do nearly anything to keep the shavings and manure off the property. You’ll often find police stables in the midst of a city, and don’t overlook racetracks where huge stables are located behind the scenes.

Fairs: Every year livestock are brought to state and local fairs, generating a great deal of concentrated manure.

Colleges and Universities: Those with agricultural or veterinary programs are excellent resources for manures and other byproducts.

Rooftop Pigeon Coops: City pigeon keepers keep the cages on the roofs of apartment buildings. While pigeon manure may be too potent to use directly, it can be mixed into rooftop vegetable garden soils or compost bins for a big fertility boost.

More Manure Sources: Pet stores (but only if it is not from cats or dogs), exotic bird breeders, petting zoos, wild animal parks.

Agricultural Byproducts

Many agricultural products must undergo extensive processing in order to become market-ready, and often there are organic byproducts that result. Some of these byproducts are in high demand such as cottonseed meal or olive pomace, which are turned over to other manufacturers. Among these processors are quality organic fertilizer makers who combine them in exact recipes for easy-to-use pellets. But pelleted organic fertilizers are expensive, if you can even find them locally. You’ll save money and enjoy a great organic garden if you research what’s available in your immediate area and whether it would make good compost or if it can be tilled straight into the soil. You’ll derive benefits similar to the pellets for a fraction of the price.

Hulls and Shells

Grains such as rice, buckwheat, and oats are encased in thin, fibrous hulls. After harvest the grains are processed and the hulls removed. Rice hulls are one of the great, undiscovered soil amendments because they resist decomposition, are lightweight, and are finely textured. Although rice is only grown in certain areas, they will be an inexpensive or free resource if they’re nearby. Contact your nearest state agricultural office to inquire whether there are any processing plants or farmers, co-operatives nearby. Often the hulls are stockpiled there and free if you pick them up.

Nuts also form within a hull, but these tend to be thick and fleshy. Inside a hard, dry shell holds the edible kernel within. The hulls are valuable because they will decompose (with time) and are excellent organic matter to hold open heavy soils such as adobe clay. Nut shells may also take a very long time to decompose, which makes them excellent as functional and decorative surface mulches depending on the type of nut. Ground walnut shells are in high demand for landscaping because of their density, uniformity, and color. Walnut hulls, on the other hand, are not useful; they’re too rich in tannin and can cause staining. Pecan shells are widely available in Southern states while almonds are a significant crop in California. Peanut shells are soft and fibrous, which makes them an excellent mulch or soil amendment. Packing houses that process fruits like peaches or cherries leave an abundance of pits, which may be of considerable value for soil improvement when they’re crushed.

Pomace

Pomace is a term given to the residue of olives, fruits, and grapes after processing, either at packing houses or wineries. Pomace consists of skins and seed fragments that contain only scant quantities of nutrients, but the seed makes a good soil amendment or addition to compost. Pomace is not as “clean” as hulls or shells, but it is usually free. It’s far easier to handle if the pomace has had time to fully air dry before you transport it. This makes it more lightweight to move and less prone to fermentation odors, particularly in the heat of summer. Grape pomace is a good product available in California and in all other American wine-producing regions.

Cotton Gin Waste

Cotton gin waste is another old-time byproduct of the Cotton Belt. Like hulls, cotton gin waste contains very little nutrition, but if obtained inexpensively enough it is useful for soil conditioning or for adding to a compost heap.

Straw

Straw is inexpensive, easy to buy, and nicely packed into an easy-to-handle bale. A bale will slide into the back of a minivan or the trunk of a larger passenger car. You can buy straw from feed stores and garden centers. Its origin is most often wheat, but you can also get rice straw and other forms unique to certain agricultural areas.

Straw is popular with vegetable gardeners as a surface mulch to block weeds between widely spaced rows and to keep your feet out of wet ground. It’s easy to transport in a wheelbarrow, and a well-compressed bale opens up to a very large mass of material. Straw is used around the bases of the plants to keep them more evenly damp during very hot weather; it also shades the root zones and keeps them cool. After straw has decomposed over a growing season, it can be tilled back into the soil in the late fall or early spring.

For new homes and freshly graded homesites, erosion control is vital to keeping runoff from carrying away exposed soil particles. Straw is the least expensive material to do that. It also is often used by highway departments to broadcast over a new slope; then it’s punched in with shovels to hold it in place over the rainy season. These anchorages make a perfect place for grass seed tossed for erosion control to lodge and grow. Anyone planting open spaces, slopes, and pastures on sloping ground will benefit from this technique.

Since straw is so easy to get, you can stockpile any excess in a corner of the garden to gradually break down. Or, open a whole bale and separate the flakes. Throw a few shovels of native soil in between each flake of straw as it piles up. This is a great way to begin a lazy gardener’s compost pile. Occasionally add handfuls of fertilizer or manure with high nitrogen content to the pile along with anything else, such as old potting soil or kitchen refuse, to introduce microorganisms. Forget it for a year or two. The result will be an excellent amendment for clay soil that will go a long way for pennies.

Cover Crops and Green Manures

In the past, farmers didn’t have the ability to haul truckloads of manure, and synthetic fertilizers weren’t available, so they learned to grow their soil fertility. For centuries farmers planted fallow fields in temporary cover crops of leguminous plants. Legumes have the unique ability to transform nitrogen from the air and transfer it into the soil where they are growing, thus leaving the ground more fertile than before. These unique plants include many different types of clover, alfalfa, and peas. After a legume plant dies, there is a lot of nitrogen trapped in its stems and roots. When legumes are tilled into the earth, they release a boost of natural nitrogen.

Budget gardeners can take full advantage of this to improve larger sites and vegetable plots. Green manure is also the best way to rehabilitate a homesite that has extensive grading and soil disturbance. Often when a house is built on subsoil, you must build the ground up considerably in order to have a successful garden.

Choosing the right legume for your region may require some professional guidance from a farm advisor or neighbor familiar with local conditions. Some legumes are sown in fall to prepare for a spring garden. You can do this every year if you wish, which will cause the soil to gradually grow richer and richer. Legume seeds are sold by organic garden outlets or local farm supply stores where they’ll know the varieties and planting times that are best for your climate.

Budget Gardener’s Secret Weapon

Planting cover crops isn’t always possible for a variety of reasons, but here’s a shortcut that achieves much the same result in the garden for only slightly more money. Alfalfa, a legume, is a common baled livestock feed, and when used to enhance soil, its nutrient content is nearly identical to that of some manures. Baled alfalfa is a compressed, preserved cover crop that you can take apart and spread throughout your garden. It can be used in lieu of straw as a mulch in the first year, then tilled in at season’s end. If you spread it in fall, run your lawn mower over the alfalfa to further chop it into smaller bits that will be easier to work into the soil in spring. Or, just spread and till it in during fall to generate nutrients and add organic matter as it decomposes over winter. This technique is a budget gardener’s secret weapon to starting a new garden on the road toward high fertility for very little cost compared to bagged compost and other similar products. Using a bale also adds ease of transportation to its features.

If you take the alfalfa idea a step further, consider yet another technique for green manure that costs a bit more–pelleted alfalfa feeds. Organic gardeners rave about these as ornamental mulches because they are an attractive and easy-to-use form of green manure. Pellets are simply alfalfa that’s been chopped up and compressed into a more manageable form that can be used on food and herb gardens as well as for ornamental plants such as roses. Distribute the pellets into the soil or around a plant and in a short time they’ll disintegrate into the ground, offering both nitrogen and organic matter.

Green Choices

Alfalfa pellets are a great alternative for urban gardeners who may not have access to much organic matter or manure. Although processing and packaging drives the price of pellets up, there is no better way to get a good start on organic gardening.

Forest Byproducts

With high prices and slowdowns in the logging industry, the cost of forest byproducts has become limited and expensive. The landscape industry uses ground bark of various conifers as decorative mulch because of its beauty, uniform color, and texture. But this is so costly that landscapers use a very thin layer useful only for aesthetics. It’s too thin a layer to obtain the other important benefits of mulching.

It takes a layer at least two inches thick to block weed germination, retain soil moisture, and shade the root zone as well as cover unattractive ground. The better choice is wood chips, the byproducts of many tree-and vegetation-related industries. The most common source is wood chips generated by tree trimming companies that chip their branches to reduce the cost of disposal. If there is a tree trimmer in the neighborhood running a chipping machine, don’t hesitate to ask if you can have the chips. Be willing to offer them a six-pack or some money for the favor and be prepared to receive a large pile in the driveway.

Landfill composting programs are one of the smartest innovations in green urban waste management. They grind up the matter into chipped mulches, which are then made available for people in the community who are willing to load and haul it themselves.

Shavings are finer than wood chips and make a useful soil amendment, particularly where soils are heavy clay. The landscape industry uses nitrolized shavings, which are treated with an extra dose of synthetic nitrogen so that they can decompose without nitrogen losses in the soil. You can buy ordinary shavings in tightly packed bales, but this is not particularly cost effective. Strive for free sources such as a high school woodshop, the super source for urban gardeners scrounging for organic matter. The same is true for cabinetmakers’ shops and lumberyards that cut wood to order for their customers. Don’t overlook woodlots where firewood is sold, too, because there you’ll find all sorts of bark and wood byproduct accumulations.

This excerpt has been reprinted with permission from The Small Budget Gardenerby Maureen Gilmer, published by Cool Springs Press.