Homemade Barbecue Pits: A Fun Way to Fertilize Your Soil

How to Improve Garden Soil with Off-Grid Cooking

Homemade Barbecue Pits: A Fun Way to Fertilize Your Soil

An ancient concept, homemade barbecue pits incorporate three things: fire, the ground, and food. Today the same concept can be employed for emergency cooking or tender slow-roasted meat. It can even improve the soil for garden vegetables.

Historical and Simple Homemade Barbecue Pits

Also called earth ovens, barbecue pits are dug into the ground to contain fire and ash for cooking. The technique is so old that archaeologists consider them a key sign of human settlement within a site. Modern earth ovens are used for ceremonial or celebratory cooking such as a Fijian lovo, Hawaiian luau, Māori hāngi, and New England clam bake. The American deep south and colonial California have used barbecue pits for several centuries to cook beef, pork, and goat.

Homemade barbecue pits can be as simple as digging a hole in unplanted garden soil, lining it with rocks and smoldering hardwood, adding the meat, and filling it back in with dirt. Knowing how to cook this way allows people to cook meat during situations where power, gas, or propane may not be available. Pit barbecue feeds large groups of people and can be used to roast a whole lamb or large hogs.

Ash in the Garden

Slash and burn agriculture, since Neolithic times cleared land and improved soil for planting. Farmers chopped trees and undergrowth before allowing it to dry and setting fire to it. The burned land was then planted at the beginning of the next rainy season. Though this technique was useful for several years, the soil was soon exhausted without trees to help regenerate nutrients. Farmers moved on, slashing and burning more land, then farming the next space for a few more years. Abandoned land again sprouted trees and brush. But while in some climates the forest floor regenerated within a couple of decades, in others the land became increasingly barren.

Burning the land improves soil temporarily because it increases potassium for healthy rootstock. It raises the pH of highly acidic soils. Ash from hardwoods contains micronutrients. Though composition can vary, the ash contains about 15 percent calcium, a necessary element for crops. Fire also destroys pests such as squash bugs which may overwinter within the soil and can incinerate diseased plants which should not be composted.

As populations increased, slash and burn agriculture became even less sustainable. Forests within temperate zones can regenerate within a lifetime and large groups of people may need the land again before trees return. Fire can also strip organisms from the soil and cause erosion. Modern farming still uses burning techniques to clear fields after harvest, but researchers urge people to find another way to reset the land. It’s dangerous, it eventually destroys the soil, and it releases carbon dioxide into the air that may contribute to global warming.

Gardeners can use ash as one of many organic fertilizers by following a few rules. Only burn in areas where soil’s organisms won’t be destroyed, such as barren patches or in holes lined with rocks. Only burn clean hardwood, not cardboard, plywood, pressure-treated or painted lumber, or barbecue briquettes which have chemical accelerants. Ash from softwoods can be used, though they have much fewer valuable nutrients for the soil.

Dry ash, applied on top of the soil, deters slugs and snails. It is useful for growing carrots, parsnips, and other root vegetables. It gives pea and bean pods a better weight and color. Fruits such as apples, pears, blackberries, strawberries, and gooseberries enjoy a little ash sprinkled on the ground then watered in. Raising soil pH helps eliminate club root within brassicas.

To use ash within the garden, first test your soil’s alkalinity. Most plants prefer around 6.5, slightly more acidic than neutral for good growth. Blueberries, marigolds, pecan, sweet potato, and other ornamentals, prefer highly acidic soil between 4 and 5.5. Wood ash should not be used near these plants. Naturally alkaline soil should have no ash added; instead, dump the ash over weeds to raise the pH so high those plants cannot survive. And in case tutorials on how to grow potatoes didn’t mention it, do not use wood ash within potato’s soil because the increased alkalinity can promote scab.

But if your soil is too acidic, dump in wood ash at twice the recommended amount for lime. For instance, if five pounds of lime is recommended, add ten pounds of ash. Use a half pound for a shrub or per square yard of the garden. 1,000 square feet of lawn needs 10 to 15 pounds. Do not dump ash onto leaves or directly at the plant’s base, and do not use with seedlings because it can burn very young plants.

Though clean ash from pizza ovens or fireplaces can be used within gardens, it’s much more fun to hold a springtime event by making a homemade barbecue pit and slow-cooking brisket or a leg of lamb within the ground.

Photo by Shelley DeDauw

Using Homemade Barbecue Pits for Gardening

To avoid killing soil organisms, dig in barren dirt or areas which will later be dug out for root cellar plans. The size of the pit depends on what you intend to cook. Extend it one foot larger, in each direction, than the entire portion of meat. A full-sized ham which may be twelve inches thick needs a hole about three feet in diameter.

Line the hole with stones or bricks to even out the heat. Avoid rocks which have been in salt water because they may crack or explode.

Building the fire takes hours. If you intend to roast the meat all night then dig it up for a noontime barbecue, start the fire before the sun even sets. Avoiding treated charcoal lengthens this time. Start fires naturally, using paper, kindling, or other non-toxic materials. Once it gets going, watch it carefully as the wood burns down to coals.

While the fire burns, season the meat then wrap it. Traditional luau techniques employ banana leaves. Modern cooks use aluminum foil. Wrap the seasoned meat first within several layers of foil, then plenty of wet burlap or old, damp towels. The use of a heavy metal frame such as poultry wire bent around the meat.

Wearing sleeves, gloves, and eye protection against sparks, carefully lower the meat into the pit. Immediately cover to keep the fire from igniting the burlap. Without oxygen, the flames will die but the coals remain hot for days. Cover with sheets of metal or dirt but be sure whatever you use seals off all oxygen. Digging the meat up later is easy because of the wire wrapped around the package.

Cook overnight or longer. A large pork butt can take twelve hours and entire pigs with vegetables may take a couple of days. Waiting too long to dig the food up rarely results in dry meat because little moisture can escape during cooking.

After the meat has been unearthed and consumed, leave the pit uncovered and let it cool completely. Scoop out wood ash and separate solid chunks of charcoal. These can be tossed into the next pit barbecue and incinerated again to create more ash. If you intend to use your homemade barbecue pit again, leave the rocks within. Or remove them and either fill the hole back in or continue to build your root cellar.

Do you use a homemade barbecue pit? What’s your favorite meat to cook?

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