Tag Archives: soil health

Summer Cover Crops

May 6, 2025 Jordan Charbonneau Leave a comment

Cover cropping is an incredibly beneficial practice for anyone who gardens. It helps improve the soil, protect the environment, attract pollinators, and so much more. Unfortunately, most gardeners think of cover cropping as a practice for the off season. However, summer cover crops have a lot of unique benefits and you can work them into your garden without giving up any production.

Benefits of Summer Cover Crops

Summer cover crops can help improve your soil health and production during the season. They also help protect your garden and the environment in several essential ways.

Reduce erosion. Usually associated with fall and winter storms, erosion isn’t a major focus in summer, but it can happen any time of year. It’s a critical issue in the United States. Scientists estimate that we’ve lost 30% of our topsoil in the past 200 years.

In summer, all it takes is a strong thunderstorm rolling through to wash away loose soil or drying winds picking up soil particles. You should never leave your soil bare.

Erosion doesn’t just negatively affect your garden health, it has significant impacts on the ecosystem. Eroded sediment and nutrients end up in streams, rivers, and eventually the ocean, where they can cloud waters and cause toxic algae blooms.

Having cover crops on the soil also allows for better water infiltration and soil structure which can help you create a more drought resistant garden.

Suppress weeds. Weeds are at their most aggressive in summer, which is why it’s a key time to get ahead of them with cover crops. Quick growing cover crops can crowd out and shade weeds, suppressing them for later vegetable crops.

Some cover crops like buckwheat and sorghum sudangrass also release chemicals to prevent the germination or growth of weed in a phenomenon called allelopathy.

You can also kill the cover crops through rolling or mulching and leave them on the surface as mulch. Then transplant crops into the mulched bed. The mulch will continue suppressing weeds as it breaks down.

Attract beneficial wildlife and insects. Beneficial animals and insects are some of the gardener’s best allies. Some like hummingbirds, flies, bees, and butterflies pollinate crops. Others like swallows, bluebirds, toads, wasps, lady beetles, lacewings, and wheel bugs feed on common garden pests, keeping their populations low. A few, like earthworms, millipedes, and pill bugs, help break down organic matter, improving soil structure.

None of these animals or insects thrive in areas with bare soil. Sowing cover crops provides cover and food sources. Some cover crops like buckwheat and hairy vetch also have flowers that may help attract predatory wasps, bees, and other pollinators.

Fix nitrogen. Certain cover crops are nitrogen fixers. These plants have a symbiotic relationship with specific bacteria. The bacteria colonize the plant’s roots and pull nitrogen out of the atmosphere. The bacteria use the nitrogen and then it becomes available to the plant.

These nitrogen-fixing plants include a few summer cover crops like southern peas, soybeans, buckwheat, sunn hemp, and hairy vetch.

To make the nitrogen available to your next crop, the cover crop needs to die and decompose. Depending on the crop, you can kill it by cutting it, tilling it under, tarping it, or waiting for frost to kill it in the fall.

Add organic matter. Fast-growing summer cover crops are a great way to add tons of biomass to the soil. As they break down, they add organic matter, which improves soil structure, increases water infiltration, provides nutrients, and increases microbial and beneficial insect activity.

Impact plant diseases. In some cases, summer cover crops may help disrupt disease cycles in the garden. Some research has shown reductions in blight in no-till, cover crop gardens.

How to Work Summer Cover Crops into Your Garden Plan

You don’t need to give up production to grow summer cover crops! There are several ways you can squeeze cover crops into the summer garden without sacrificing your vegetables.

Use pathways. If your garden has pathway space, you can take advantage of it by sowing it in a cover crop like white clover which will tolerate some traffic. You can mow the paths and apply it as mulch under other crops.

Interplant. You can also interplant cover crops. Strips of clover, vetch, and other cover crop can have amazing benefits. According to the North Carolina State Extension, “research in Georgia reported high densities of big-eyed bugs, lady bugs, and other beneficial insects in vetches and clovers.” They also found that, “assassin bugs have destroyed Colorado Potato Beetle feeding on eggplant planted into strip-tilled crimson clover.”

You can grow some cover crops in between other crops. Plant soy beans or southern peas beneath tall crops like corn or sunflowers. You can also grow fast-growing cover crops like buckwheat between hills of vining crops like winter squash or melons. Cut the buckwheat as the vine start to sprawl and use it as mulch.

Pull unproductive crops immediately. If your lettuce has bolted, radishes have gone woody, or beans are slowing down, consider pulling them and sowing a summer cover crop. While letting lettuce flower and beans decompose naturally may provide some minor benefits, using a cover crop is a more productive use of the space.

Beat the heat. In the Deep South, the hottest days of summer can limit vegetable production. Rather than fighting the heat to eek out more production, you may just want to avoid it. For some crops like brassicas, greens, bush beans, and cucumbers, you can get plenty of production in the early summer and fall.

Take well-earned breaks. If you find your garden is getting away from you and your summer is busier than expected, it may be worth sowing a cover crop rather than another succession. A cover crop will essentially take care of its self while improving your soil for another crop in the fall or next season. Sometimes this is more productive than sowing more beans, squash, or other vegetables you won’t have the time to weed, harvest, and preserve.

How to Select a Summer Cover Crop

All summer cover crops have their pros and cons. What cover crop you should choose will be based on a few factors:

Time Available
It’s easiest to choose and appropriate cover crop when you have a good garden plan. Maybe you want a heat tolerant cover crop to grow for 30 days in the middle of summer in between squash plantings. Buckwheat may work in this scenario. Maybe you have an empty bed 80 days before your first frost and want a cover crop that will die back and allow you to plant fall garlic. Sunn Hemp could be a good choice.
Frost Tolerance
Some summer cover crops like buckwheat, are frost sensitive and will die with the first frost in fall. Others, like clover and oats, will continue to grow.
Nitrogen Fixation
If your next crop is a heavy feeder like broccoli, corn, garlic, onions, or tomatoes, choosing a nitrogen fixer like sunn hemp, hairy vetch, clover, soy beans, or southern peas is a great option.
Biomass Production
If adding organic matter to the soil is a priority, you’ll want to choose a cover crop that quickly puts on a lot of biomass. One of the best options is sunn hemp which can reach 6 feet tall in 60 days. Other good options include buckwheat, millet, sorghum sudangrass, vetch, oats, and barley.

Here are a few summer cover crops you may consider. Listed with each are some of their important features.

Buckwheat

Blooms and is ready for incorporation in 30 to 45 days.
Fast growing.
Frost sensitive.
Flowers attract bees and parasitic wasps.
Tender stems are easy to cut down.
Deep root system is adept at mining subsurface minerals.

Pearl Millet

Ready for incorporation in 40 to 60 days.
Grows well in acidic soil and poor soil.
Thrives in warm climates.
Drought tolerant.
Excellent biomass producer growing 3 to 6 feet.
Frost sensitive.

Sunn Hemp

Ready for incorporation in 60 to 90 days.
Fast growing and excellent producer of organic matter (may reach 6 feet).
Nitrogen fixing.
Frost sensitive.
Suppresses nematodes.
Thrives in hot climates.
Tolerates drought.
Extract nutrients from deep within subsoil.

Soy Beans

Ready for incorporation in 45 to 60 days.
Fast growing.
Tolerates hot weather.
Nitrogen fixing.

Southern Peas

Ready for incorporation in 50 to 60 days.
Vigorous.
Drought tolerant.
Nitrogen fixing.
Sprawling vines.

Sorghum Sudangrass

Ready for incorporation in 60-70 days.
Suppresses weeds.
Suppresses nematodes.
Loosens subsoil and reduces compaction.
Excellent biomass producer growing 5 to 12 feet tall.
Provides habitat for beneficial insects like lacewings.
Requires a large mower and is tough to cut with hand tools.

Oats

Ideal for late summer and early fall planting.
Grows quickly.
Produces plenty of biomass or mulch.
Frost hardy.
Oats will get winter-killed when temperatures drop below 10°F.
In cold climates, it makes an excellent mulch for spring crops and in arm climates you can cut it in spring.

Barley

Ideal for late summer and early fall planting.
Frost hardy.
Drought tolerant.
Barley will get winter-killed when temperatures drop below 17°F.
In cold climates, it makes an excellent mulch for spring crops and in warm climates you can cut it in spring.

Hairy Vetch

Ideal sowing period from August 1st to November 1st.
Highly efficient as a nitrogen fixer, it’s recommended to wait until at least 50% of the plants have flowered before mowing the crop to maximize nitrogen fixation.
In the spring, after flowering starts, mow the vetch and transplant tomatoes or other large plants directly into it, or till it under.

Clover

Cold tolerant perennial.
Versatile and may be sown in winter, spring, late summer, or fall.
Excellent for suppressing weed growth.
Nitrogen fixing.
Attracts beneficial insects.
Acts as a living mulch in paths or between rows.

Creating a sustainable, productive garden means that we’re focusing on soil health year round. As you plant and plan your garden this season, think about where you may be able to sneak in a few summer cover crops.

Garden Advice

Biochar 101

July 17, 2023 Jordan Charbonneau Leave a comment

Spend enough time reading about sustainable agriculture, and you’ll inevitably run into the word biochar. In recent years it has seen a surge in popularity and is often touted as an amazing, organic garden amendment. But what is biochar, and is it great for the garden? Today, we’ll dig into what biochar is, what it does to soil, how it’s made, and how indigenous farmers have utilized it for thousands of years.

What is Biochar?

Biochar is a type of charcoal made from biomass or plant material that has been burned or decomposed in a controlled, hot, low-oxygen process called pyrolysis.

In other words, wood chips, leaf litter, twigs, dead plants, or other similar materials are burned in a container that allows very little oxygen to enter. This process produces little to no contaminating fumes.

Biochar is lightweight, highly porous, and has a large surface area. Biochar is approximately 70 percent carbon but contains nitrogen, hydrogen, and oxygen, among other elements depending on the materials. Its exact composition depends on the plant material and temperature and the time it was processed. The University of Tennessee Extension Service has some wonderful charts on Biochar effects and macronutrient contents.

The Benefits of Biochar

You can use biochar as a soil amendment or conditioner in your garden soil or containers. Biochar proponents recommend biochar for its benefits in the garden and the larger environment.

Biochar’s Soil Benefits

Biochar may increase cation exchange capacity (CEC), a measure of the soil’s ability to hold positively charged ions. CEC influences soil structure, nutrient availability, soil pH, and soil’s reaction to fertilizer and other amendments.
Biochar may enhance water-holding capacity.
Biochar may increase soil surface area.
Biochar may increase plant nutrient availability.
Biochar increases soil pH.

Biochar’s Environmental Benefits

Biochar sequesters carbon in the soil.
Biochar may increase agricultural productivity.
Biochar may help improve soil water filtration.

Biochar Origins: The Amazon Basin

Agriculture is one sphere where some of the greatest minds, particularly those of BIPOC folks, have never gotten the credit they deserve. Biochar is likely one of those cases.

When the Portuguese first began to explore and colonize the Amazon Basin, they were surprised to find sections of dark rich soils surrounded by common, less fertile Amazonian soil. They called these soils terra preta de índio or “Indians’ black earth.”

Unsurprisingly, Europeans did not immediately attribute these high-quality soils to the work of indigenous farmers. Instead, many Europeans thought they resulted from natural causes such as ash fall from Andean volcanoes or sediment from long-ago lakes and ponds.

Today, the content of these soils, which commonly includes tiny pottery shards, fishbones, and other residues from cooking and habitat, tells us otherwise. The indigenous peoples that called these lands home undoubtedly improved these soils with biochar and other amendments, probably beginning between 450 BCE and 950 CE. Through carefully crafted management, once-infertile soils had been made suitable for large-scale agriculture.

Sadly, the descendants of these careful farmers were forced to give up their more agrarian lifestyles, probably in the 16th and 17th centuries, as they faced the effects of colonization. The peoples of this region were hard hit by introduced European diseases and violence, including Bandeirante slave-raiding.

To escape colonization, many likely took up a more nomadic lifestyle. Slash-and-char style agriculture may have been an adaptation of older farming techniques to cope with their migratory lifestyle.

Each year, the soils in the Amazon basin are exposed to warm tropical temperatures and about 80 inches of rainfall. The fact that these incredible soils still exist today, after about 500 years, is a testament to the power and knowledge of indigenous farmers.

A hand holding a piece of biochar in front of a barrel full of it — Homemade biochar

Making Biochar

Today, you can purchase biochar, but with a little time and effort, you can also make your own.

One of the simplest methods for making biochar is to do it right in the garden. Dig a trench in your garden bed and fill it with brush and plant material. Light this material on fire, and once it’s burning well, cover it with an inch or so of soil to reduce the available oxygen. This method is easy but also the least efficient way.

A slightly more efficient method is to place your material in some sort of closed container in a fire. You can do this with an old metal barrel, pot, or pan. Place your material in your container, then build a fire beneath and around the container to heat it.

Pyrolysis equipment is the most efficient route and is available for those who would like to produce large-scale or commercial biochar. Biochar.co.uk has some great information and resources for any level of biochar production you may be interested in.

If you run a wood stove in winter, Edible Acres, a permaculture-focused Youtube Channel, also has an excellent video on experimenting with making biochar in a wood stove.

Please check your local laws and regulations before doing any burning. Stay safe, always watch your fires, and always have a good water source immediately at hand.

Biochar can be a great way to improve your soils without paying for expensive truckloads of topsoil, fertilizer, or other amendments. Its properties and benefits may vary with each batch of biochar and the garden you use it in. Let us know in the comments if you’ve had success with biochar!

Garden Advice

Can I Use Manure On My Garden?

July 3, 2023 Jordan Charbonneau Leave a comment

An abundant source of manure can seem like garden gold, especially for those moving away from commercial fertilizers. Manure provides important nutrients, improves texture, and increases soils’ water-holding capacity. However, like anything else in gardening, manure isn’t always a perfect solution. Here are a few things you should know if you’re considering using manure on your garden.

Using Manure Properly

Manure may be full of nutrients, but it can also contain bacteria. Some of the bacteria in manure can be transmitted to humans via vegetables if it’s not properly handled and applied to the garden. While many small gardeners feel perfectly safe using manure, especially from their own livestock, you should still generally avoid using fresh manure around crops that may come into contact with the soil.

If you’re looking for good guidelines, the USDA National Organic Program has standards for handling fresh manure. These are especially important if you sell or hope to sell some of your produce.

USDA National Organic Program (NOP) Standards

The NOP has specific rules for when growers may apply non-composted manure to their gardens.

If you’re using manure on crops with an edible portion that may come into contact with the soil, you must apply the fresh manure 120 days before harvest. This rule includes vegetables that come into direct contact with the soil, like carrots and melons, and those that may come into contact with it from irrigation or rain splash, including leafy greens, peas, and beans.

Fresh manure can be incorporated into the soil up to 90 days before harvest for crops that don’t have an edible portion that touches the soil, like tree fruits and sweet corn.

Note that the 90- and 120-day restrictions apply only to food crops; they do not apply to fiber crops, cover crops, or crops used as livestock feed.

Avoid Run-Off

When applying fresh manure to gardens, you also want to avoid run-off. Manure running into local streams, storm drains, and other waterways can lead to excessive amounts of nitrogen and other nutrients in the water, which may cause toxic algal blooms. To help prevent and control run-off, you can plant cover crops, better incorporate the manure into the soil, and create berms or swales.

Composting Manure

Alternatively, you can compost your manure. To kill bacteria and pathogens in compost, you’ll need reasonably high composting temperatures, between 131-170°F (54-60°C), for several days. These temperatures will also kill parasites, weed seeds, and harmful fungi.

Herbicide Contaminated Manure

The widespread use of commercial herbicides has also presented another issue for gardeners. Manure from animals that have eaten hay or forage from fields that were treated with aminopyralid or related herbicides like clopyralid or picloram may be contaminated. Animals’ digestive systems do not filter these chemicals out. Therefore, adding their manure to gardens can severely damage legumes like beans and peas, solanaceous crops like tomatoes and peppers, and other broadleaf crops. You can check for herbicide residues at home with a bioassay test.

Bioassay Test

You’ll need 6 to 10 pots and seeds or seedlings to conduct a bioassay test. In its simplest form, you will check and see how seedlings grow in soil you know to be safe compared with how seedlings grow in soil mixed with the unknown manure.

Fill half of the pots with soil you know is good quality and free from herbicides, like soil from your own garden. Fill the other half of the pots with a one-to-one mixture of soil and manure. When you collect manure for this, take samples from different areas and depths in the pile and mix them together.

Then plant the same type of seed or transplant the same age and type of seedling in each pot. Observe their growth over the next three weeks. Make notes on the plant’s overall growth, including the leaves and roots. Watch for signs of stunted growth, discoloration, abnormal growth, curled leaves, root swelling, or stunting.

The North Carolina Extension Agency has further instructions for Bioassay tests and a helpful table covering some recommended bioassay species for residual herbicides and the expected injury symptoms.

Can I Use Pet Waste?

No, you should not use pet waste in the garden or compost it for use in the garden. Waste from cats and dogs may contain heavy metals, bacteria like E. Coli and Salmonella, as well as parasites like tapeworms and ringworms.

If you need to get rid of pet waste, make a separate compost pile, and don’t use it on the garden.

If you have a pet rabbit, their waste is safe for the garden as long as you use compostable litter.

Can I Use Human Waste?

It sounds weird, as most of us in the United States have modern plumbing, but the idea of using human waste on crops isn’t new. Until about 400 years ago, adding human waste back to the soil was commonplace.

Today, this practice is mostly followed by off-grid and sustainability enthusiasts. If you’re interested in these topics, you may have heard of “The Humane Handbook,” written by Joseph Jenkins in 1995, which helped to make waste composting systems more popular.

If properly managed, human waste can be safely composted and used. That said, you’ll need to be set up for it. Even then, you should only use human waste when it’s fully composted and only use it around fruit trees and ornamental plantings.

Manure is a wonderful garden amendment when handled properly. If you want to use manure in your garden, follow these steps to ensure it doesn’t contaminate your garden with herbicides or bacteria.

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