nematodes, and more), look up “biological soil testing” or send a sample to a lab such as Earthfort (earthfort.com).
Make Amends
Once you know the nutrient levels of your soil, you can amend accordingly. Soil amendments—also called inputs—can increase available nutrients, but they also can alter soil texture or improve drainage. Let’s revisit the soil textures: clay, silt, and sand. What can you do to improve these conditions?
Surprisingly, the organic solution to hard-packed clay soil, compacted silt, and loose, anemic sandy soil is one thing: compost. In clay and silty soil, compost serves to create space between particles and allow more airflow, which then helps the soil drain better. In sandy soil, compost works as a sponge to retain moisture and provides structure to hold nutrients. Compost brings these extreme conditions closer to the perfect texture for growing vegetables and fruits; this ideal is called loam. Loamy soil holds nutrients but drains well. It supports the easy proliferation of root systems and is nearly effortless to dig. Loam is the goal that every gardener hopes to attain with soil.
So how much compost should you apply to your soil? The general rule of thumb is to add compost in inches. Add a 1/2- to 1-inch (1.25- to 2.5-cm) layer at the beginning of each season before planting and, if needed, again during mid-season to boost production. You can either top-dress, meaning spread it out on the surface and leave it, or you can work it into the top few inches (7 or 8 cm) of soil. Soil food web aficionados prefer to apply compost on the surface, without disturbing the delicate strands of fungal hyphae and microbial life hard at work in the soil. The microbes will utilize the compost as it filters through the soil during regular watering and as larger insects and earthworms till it into the soil for you. All of this activity makes nutrients available to plants with less work from you.
Gardeners with very sandy soil may choose to ignore the 1/2- to 1-inch (1.25- to 2.5-cm) rule of thumb and add compost with reckless abandon. It’s OK. Add compost, then add more compost, and when you think you’ve added enough, add more. Your soil will be just about right at that point.
In addition to benefiting soil texture and structure, compost adds nitrogen and inoculates your soil with those stagehands we talked about earlier. Compost does much more than feed the soil; it brings it to life with fungi, bacteria, microscopic insects, and earthworms. It supercharges your soil with the microbiology needed to help plants thrive. You can buy bagged compost from nurseries, but why not make it yourself? It’s a great way to recycle nutrients in your garden and cut down on waste that goes to the landfill. Food waste happens to be one of the top contributors to climate change, by the way. So if you aren’t composting, now is a great time to start! Best of all, making your own compost means you know exactly what’s in it, and you don’t have to drive anywhere to get it.
Start a Compost Bin
A compost bin can be any structure that holds garden biomass (use this term instead of waste, because you’re not wasting anything). A compost bin can be a cylinder of hardware cloth, an old trash can with the bottom removed and holes punched in the sides, or an official store-bought compost bin. You don’t even need a bin, per se, to store your compost. You can make a pile in your backyard and let it cook. The important thing is to start using your own garden biomass to give back to your garden. Here are a few guidelines for creating a viable composting system.
Compost is a valuable soil amendment in many situations.
Size: The ideal minimum size for a compost bin is 3 x 3 x 3 feet (0.9 x 0.9 x 0.9 m). That is the magic size at which organic mass begins to generate and hold heat.
Space: Allow enough space for your compost bin or pile, plus enough space right next to it for another pile. Why? At some point you will want to “turn” the pile (to aerate it and expose new surface area to all of those microbes that will continue to break down the organic matter, which makes the pile heat up again), so ideally you can use that space next to your compost pile to flip a pile from one side to the other without exerting much effort.
Browns and greens: Composting is a chemical reaction between carbon (usually brown-colored biomass) and nitrogen (often, but not always, green-colored biomass). Carbon-rich materials like dried leaves, wood chips, dead corn stalks, wheat chaff, and cardboard are combined with nitrogen-rich materials like kitchen scraps, coffee grounds, grass clippings, cover crops (such as fava beans, alfalfa, and bell beans), and garden trimmings to start the process. See Appendix A for an expanded list of browns and greens.
Other ingredients: Compost requires moisture in order to break down brown and green biomass. Water is a key ingredient. In climates with regular rainfall, you may never need to water your compost pile once it’s built. In fact, some gardeners have to cover their compost piles with tarps to keep them from getting too wet (excess moisture promotes anaerobic bacteria—the kind that stink). In dry climates, though, you will need to water your pile regularly. Start by thoroughly watering each layer of the pile as you build it. If you use alfalfa or straw, it will take a lot of water to wet the material completely. Be patient and don’t be afraid to use plenty of water. According to Alane O’Rielly Weber, a certified Soil Foodweb advisor at Botanical Arts in San Mateo, California, you should be able to squeeze a drop of water out of a handful of biomass. If not, it’s not wet enough. A helpful tip to use as a guideline for moisture is that your pile should be wet like a wrung-out sponge. Water begins the process of biodegradation and invites beneficial microbes to feast upon the decaying matter, so it’s a really important ingredient in your pile.
Soil: Soil is another key ingredient, and it is often omitted from many composting guides. You don’t need to buy those silly boxes of “compost starter”—use soil instead! Healthy soil inoculates your compost pile with fungi, bacteria, and microorganisms, which go to work to break down organic matter, to aerate the pile as they crawl through, and to digest material. The result is high-powered, high-vitality compost that improves your soil with every application.
Layers: Composting guides vary and will tell you that the ratio of brown material to green material ranges anywhere between one part brown and two parts green to five parts brown and one part green. It can get confusing. Keep it simple. Use depth instead of parts or volume measurements. Put down a 2- to 3-inch (5- to 7.5-cm) layer of browns, then a 2- to 3-inch (5- to 7.5-cm) layer of greens, and then a shovelful of soil, and water it in. Repeat this process until you have used up your ingredients.
Three compost bins at Gardenerd HQ
Geek Alert: Active Batch Thermal Composting
If you want to get more technical and build an amazing compost pile, try this method for active batch thermal composting. Wait a minute. What the heck does that mean?
Active—you are turning the pile and monitoring temperatures.
Batch—you are building the whole pile all at once rather than adding materials over time.
Thermal—it gets hot, up to 160° Fahrenheit (71° Celsius), with the right materials.
Composting—you are breaking down garden biomass into black gold.
Here’s the method: Figure out how much material your compost bin will hold in gallons (liters). Next, gather your browns and greens in 5-gallon (19-L) buckets using the following ratio that Dr. Ingham recommends for beneficial bacterial-dominated compost, which is great for vegetable gardens:
35
