Repurpose These 3 Waste Products For Building Garden Soil

Soil amendments, fertilizers and mulch don’t have to be a financial strain on your farm’s budget. Here are three resources you already make at home—for free!

by Frank Hyman

Cold weather and the holidays mean you’ll likely be starting off the new year with plenty of wood ash, wine corks and the liquid byproduct of all those adult beverages. Resolve to make your life easier through better use of household waste products: Turn them into garden resources instead.

1. Wood Ash

One of the most effective soil amendments a hobby farmer can use is lime. If you live in a part of the country with high rainfall (20 inches or more per year), such as the Pacific Northwest and states east of the Mississippi, you may need to spread lime every three years to counteract the acidity in the soil. No matter how much fertilizer you apply, acidic soil—one with a low pH of around 5—blocks plant roots from getting at those nutrients. Lime reduces acidity, usually raising pH to about 6.5, and acts like a key to unlock those nutrients. If you’re burning wood for heat, you can raise the soil pH for free by spreading wood ash instead.

In fact, our country’s first patent, issued on July 31, 1790, was signed by George Washington and presented to Samuel Hopkins for a method of producing wood ash. Wood ash was also one of the first commodities that the American colonies provided England.

Wood ash has about 1/4 to 1/2 as much calcium as lime, but because wood ash comes from plants, it also supplies a dozen other micronutrients and has an NPK ratio as high as 0-1-10. Lime only supplies calcium and perhaps magnesium. In other words, wood ashes provide the same acidity reduction as lime, but due to the extra nutrients, they can be used as a fertilizer to promote better crop growth.

One cord of hardwood produces about 25 pounds of wood ash. (Ashes should be kept in a metal container until they cool.) A 5-gallon bucket can hold 15 to 20 pounds of cooled ash. As a rule of thumb, that could be enough to sustain a soil pH of about 6.5 in a 1,000-square-foot bed. Conifer wood, from pine and spruce trees, produce half as much ash and should not be burned indoors, as it will choke your chimney with creosote. Also, don’t use ash from coal, plywood, and treated or painted wood, as some of the chemicals present in them would remain in the ash and poison your soil.

Before applying hardwood ash, get a soil test and a test of your wood ash composition from your state agricultural extension service. This will guide you on how much to apply to keep your pH at an optimum level.

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Generally, lime is applied once every three years, and you may already know how much lime to apply to your land. And because, on average, wood ash may be a third as strong as lime, you can ballpark your ash application levels by putting out the same amount of ash every year as you would lime every three years.

Testing soil and ash can keep you from accidentally overshooting and raising pH and potassium levels high enough to inhibit growth. Don’t apply ash to soil that is already alkaline, such as in low rainfall regions or on beds holding blueberries and other acid-loving plants. Also, keep fresh ash away from seedlings, as it’s too salty and will burn the roots.

Wood ash is dusty when dry and caustic when wet. It can be applied year-round, but don’t spread it on a windy or rainy day. Depending on quantity, spread ashes with a trowel, lime spreader or manure spreader. Chunks of charcoal don’t have to be screened out, but if you do remove them, toss them in the compost where they’ll soak up nutrients that will feed the soil even more. Wear a bandanna, gloves and long sleeves to protect yourself, and add ash spreading to the long list of ways that heating with wood can warm you up.

2. Peecycling

You can buy a popular liquid fertilizer that’s an unnatural shade of blue, but why spend the money when you can apply your own liquid fertilizer of a natural yellow color for free?

Since 2012, the folks at the Rich Earth Institute in Brattleboro, Vt., have recruited 170 volunteers for an experiment in pee-cycling. They’ve donated their essentially sterile urine—ammonia kills pathogens—for use as a fertilizer on experimental hayfields.

The results show an increased harvest of four to six times as much hay as the control field, and that should be no surprise. A year’s worth of one person’s pee is almost enough to safely fertilize all the food that person would consume in a year. The amount of pee produced in the United States equals almost 9 billion pounds of nitrogen fertilizer. Almost all the nitrogen that humans excrete is in the urine, and nearly all the pathogens are in the fecal matter.

In the absence of peecycling, farmers often use nitrogen made from fossil fuels. Organic nitrogen fertilizers made from food waste are better for the environment, but both are shipped long distance using fossil fuels, which adds to climate disruption. Why not use homemade nitrogen fertilizer instead?

But because the 30 billion gallons of pee Americans produce in a year doesn’t go onto farms, where does it go? If it’s not going to a septic tank on your property, then at your home, school, work and other public places, it’s being mixed with fecal matter and flushed into pipes with waste from restaurants and other businesses.

At a sewage treatment plant, your municipality then spends an exorbitant amount of money making the water clean enough to dump into the drinking water supply of the next downstream community. There, the cycle is repeated ad nauseam until the water reaches the ocean, perhaps causing fish kills from excess nutrients along the way.

How can you take advantage of this resource on the farm? With enough privacy, urine can be applied directly to the soil. In the bathroom, there are two options. If you’re a man, pee into a big, plastic bottle (one that’s opaque may be more popular) and then dilute it 1:10 with water so that the salts aren’t too strong for small plants. If you’re a woman, you’ll want to try ­fashioning a way to sit down on a modified watering can or use what’s called a female urination device if you don’t want to be left out of the fun.

I’ve used a bottle for a few weeks but at a lower dilution rate. The plants I’d been fertilizing actually did worse than the ones I left alone because it was too salty, which slowed their growth. Sticking to the 1:10 dilution got much better results. One concern about these methods is the smell from the container, but I found a small amount of any cooking oil creates a thin layer between the pee and the air to keep the smell down—the small amount of oil will then break down in the soil.

Until research suggests otherwise, refrain from peecycling if you’re sick or on medication.

A good winter project would be to install a urinal or repurpose a sink that leads to an outdoor spigot with a four-way manifold. Peeing in the urinal and running the water would flush the urine to one of several soaker hoses in various garden beds. I’m already looking at a spot in our mud room for a repurposed sink my wife and I both could use to irrigate and fertilize the figs, raspberries and blueberries. I think I’ll drink a beer while I sketch out this project.

3. Cork Mulch

Don’t throw away corks you pop from champagne and wine bottles: They’re organic and can be reused.

Corks are actually a renewable resource. Farmers harvest a layer of bark from cork oaks in Portugal and Spain about every nine to 10 years. The trees regrow their bark so farmers can harvest from each tree many times over its life. The acorns from the oaks feed free-ranging pigs that produce some of the world-famous hams of the Iberian Peninsula, meaning that the move towards plastic corks could undermine one of the most sustainable agricultural systems on the planet.

Meanwhile, gardeners are throwing real corks away when they could be repurposed as pot-filler for orchids and as a permanent, attractive mulch for container plants, such as dwarf citrus trees.

A number of our houseplants also enjoy the consistent moisture of having mulch covering the potting soil, and the gaps between the corks leave room for watering in an annual dose of dry organic fertilizer.

Just tossing corks into a pot won’t work very well, because they’ll float around as you water them. The best practice is to make sure there’s room for the corks with a clearance of 1 to 2 inches between the potting soil surface and the top of the pot. Then slip a piece of wood about an inch thick under the side of the pot facing you. Start standing the corks up at the back of the pot and work your way to the front. Once the pot is full, start squeezing corks into any gaps until it won’t hold any more. When they are all snug, you won’t have to worry about them floating away when you water the pot. If you’re not a big drinker, ask the bartender at your favorite restaurant to save corks for you.

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