Biochar: Ancient Soil Amendment

As we continue to learn about gardening, we are often reminded of nature’s essential role in the process, and, by extension, the wisdom demonstrated by historical gardeners as they worked in concert with nature.

We have countless examples of the benefits of “gardening with nature,” and ample evidence of the short-sightedness of technology-based agribusiness.

”Technology” as used here encompasses monocropping, animal feedlots and synthetic fertilizers and pesticides, as well as more constructive activities such as the use of drone aircraft to monitor crops.

One fascinating historical instance of natural gardening is biochar. The briefest definition of biochar is organic matter that has been heated to high temperatures with limited oxygen to produce charcoal. This process (pyrolysis) also produces gasses that can be burned to produce electricity.

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Biochar is very similar to charcoal, which is made principally from wood, and used in backyard barbecues and a variety of industrial processes. Biochar, by contrast, is made from all kinds of organic waste, particularly garden or agricultural waste, and is used as a soil amendment, adding carbon to the soil.

 

Note: The biochar photo is from a good article by Jeff Cox in Rodale’s Organic Life.

Biochar apparently has been produced and used for thousands of years by early gardeners in Brazil’s Amazon River Basin to improve their rather poor soils. In 1870, an American geologist and explorer discovered and reported areas of dark and highly fertile soil. Researchers puzzled over the origin of this unusual soil, called “terra preta” but recognized that it has strong benefits for agriculture.

During the past twenty years or so, scientists have attributed several valuable properties to biochar, beyond improving crop yields. The additional benefits include increasing water-holding capacity of soil, reducing the need for chemical fertilizers, reducing natural emissions of greenhouse gasses (nitrous oxide and methane) from agricultural soils, increasing soil microbial life, resulting in carbon sequestration, avoiding the natural decomposition of agricultural and forestry waste and thereby decreasing carbon dioxide emissions.

These benefits are stimulating great enthusiasm for uses of biochar in both gardening and agriculture. For example, scientist James Lovelock, author of The Gaia Theory, has written, “There is an outside chance that one procedure could really turn back the clock on Global warming and that is burying carbon. All you have to do is get every farmer everywhere to make a profit by turning all his agricultural waste into char and burying it.”

This success story has only an outside chance because it assumes universal participation by the world’s farmers, but does reflect the genuine value of biochar.

Still, individual gardeners could help to reverse global warming by using biochar. This material is available commercially, but it’s costly. A quick survey of sources on the Internet shows a typical price around $30 per cubic foot, enough to amend a garden bed of twenty-four square feet.

A gardener could produce biochar with little or no expense. Here are brief directions from Barbara Pleasant, Mother Earth News (2009): “Pile up woody debris in a shallow pit in a garden bed; burn the brush until the smoke thins; damp down the fire with a one-inch soil covering; let the brush smolder until it is charred; put the fire out.”

For more on this topic, visit the International Biochar Initiative.

Biochar could increase dramatically the fertility of your soil, and help you to rival the successes of ancient gardeners of the Amazon Basin.

More

A reader’s query and my reply.

Q: I read your article in Friday’s Sentinel about biochar. I am wondering if I can put used, regular, charcoal from the grill in the garden. There is always some left over. Can I break it up and put it in my garden?

It seems like I read somewhere years ago I could, but I can’t remember.

A: By “used charcoal” do you mean ashes?

I have attached a short article that is about Colorado’s soil, but California soil also tends to be alkaline, so the article has relevance in our area as well.

Charcoal is Not a Good Soil Amendment in Colorado

The bottom line is that charcoal ash, which is alkaline, would have some value when added to very acidic soil, i.e., low pH, but doesn’t add any fertility to the soil.

On the other hand, unburned, or partially burned charcoal briquettes (made from wood) could be useful as a soil amendment, although they have less nutrient value than biochar, which is made from a range of vegetative materials.

Charcoal briquettes usually contain cornstarch as a binder, and might include coal, lime and other ingredients, none of which would be harmful in the garden. Soften them in water to break them down, then dry the result to mix into fertilizers or directly into the soil.

I hope this is helpful

Another reader’s comment: 

Dylan Gillis

Fine article, though it sort of glosses over the fact that biochar itself is 99% carbon that stays in the soil for hundreds if not thousands of years. While compost only costs $3 or more per cubic foot (depending on quality, volume you buy and packaging/marketing variables) it needs to be replaced every year, forever, to result in similar levels of carbon sequestration and fertility. Of course the best is to add biochar, once to satisfactory levels, and then amend with compost for the nutrients and energy feeding the soil life, every year. In this approach you would use less compost to get the same or better results and your carbon sequestration would be more or less permanent!

Gardening to Save the Planet

We are learning about humanity’s many impacts on the near and distant future of our planet. Some people are in denial about these impacts, while others are concerned and ready to do whatever we can to ensure that our Earth will support future generations.

To support and encourage such positive action, leading botanist Peter Raven will visit the UCSC Arboretum next week to meet with UCSC faculty and staff, and present a public talk, “Saving Plants, Saving Ourselves.” Raven will present an informed update on the increasing threats to Earth’s environment, and emphasize the special role of public gardens in conserving plants that could be lost through habitat loss and climate change.

Peter Raven has a long friendship with the UCSC Arboretum, and a national reputation as a conservationist and advocate of global biodiversity: Time magazine hailed him as a Hero of the Planet. His visit to the Monterey Bay area inspires us to reflect on the home gardener’s unique role in saving the planet.

Here are ten everyday practices that gardeners can apply to help sustain the environment and protect plant diversity.

  • Irrigate your garden wisely, using drip technology to deliver water only where needed, and mulch (organic or inorganic) to minimize evaporation and weed growth.
  • Recycle household water into the garden, using plant-friendly soaps and detergents.
  • Prune your acquisitions of consumer goods that bury our landfills and clutter our environment…and that you really don’t need.
  • Propagate plants that Nature’s pollinators (bees and other insects, bats and birds) love and need to survive. Clusters of flowering plants will enrich your landscape.
  • Conserve biodiversity by protecting endangered species and including rare and threatened California native plants in your landscape. (Visit the California Native Plant Society’s website, www.rareplants.cnps.org/ for info.)
  • Nourish your plants with organic fertilizers, and discontinue uses of artificial chemicals
  • Control plant-eating insects with insect predators and organic insecticides. Use physical barriers and non-toxic deterrents to control other plant-eaters, e.g., snails, gophers and deer,
  • Select plants that are native to California or other summer-dry climates, to enable their healthy growth, support wildlife and ease your gardening workload.
  • Compost the “carbon-rich” fantasies of climate change deniers with the “nitrogen-rich” facts of the world’s scientists to promote wise stewardship of the environment. (Alto, keep all biomass on the property by composting green garden waste!)
  • Cultivate these good practices among your friends and neighbors.

The UCSC Arboretum employs these practices regularly, and assigns high priority to its work in plant conservation.

pt sur Austin and Tim

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This photo shows UCSC student Austin Robey and Arboretum volunteer Tim Forsell as they replanted endangered California native manzanita shrubs on a steep slope near the Point Sur State Historic Park and Lighthouse. The Arboretum’s Brett Hall coordinated the conservation project.

Your practices in your own garden also could help to save the planet. A good start would be to attend Peter Raven’s talk..

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Registrations for the Peter Raven talk sold out quickly. To receive timely announcements of future events at the Arboretum, visit arboretum.ucsc.edu/get-involved/.

If you would like to sponsor an educational event at the UC Santa Cruz Arboretum, contact Jennifer Macotto, 831-427-2998 or jmacotto@ucsc.edu.

For information on how you could help save a rare species: visit arboretum.ucsc.edu/education/plant-sponsorship/.

Garden Priorities for March

Despite our current, most welcome rains, we remain below the normal precipitation level for this time of the year and water conservation in the landscape continues to be important.

Conserving Water

For long-term conservation, plant California native plants or other drought-tolerant plants from the world’s Mediterranean climates. Succulent plants are increasingly popular for this reason, and for their varied forms, textures and colors, and low maintenance needs. (Desert conditions are not ideal for succulents: all need some water and quick drainage, and many enjoy partial shade.)

Shorter-term water conservation strategies include composting and mulching to retain water, using drip irrigation for efficiency, selecting vegetable varieties for low water requirements, eliminating seasonal weeds to reduce competition for scarce water, and irrigating only when plants need water. See “More” (below) for water conservation tips from Master Gardeners.

Fertilizing

Garden priorities for March include fertilizing trees, shrubs and perennials when they begin to show new growth.

For roses, give each plant two cups of a balanced fertilizer, i.e., 10-10-10 or 12-12-12, plus a quarter-cup of Epsom salts, two cups of alfalfa, and a half-cup of rock phosphate or bone meal.

There are differing views for fertilizing some plants. With bearded irises, for example, some growers recommend just a generous handful of a balanced fertilizer for each plant; others advocate low-nitrogen fertilizer, e.g., 6-10-10, plus bone meal and superphosphate. (The thinking is that adding more nitrogen could encourage root problems.)

Pruning

March is a good time for pruning still-dormant trees and shrubs, following recommendations for each plant. Here are examples from my garden:

Thin a large Wild Mock-orange (Philadelphus lewisii) by cutting about one-third of the larger branches to the base of the plant.

Shape a large Milkflower Cotoneaster (C. lacteus) by removing old, unproductive limbs and spindly branches, and generally lifting the canopy to provide more sunlight to the understory.

Renew Salvias by cutting old growth to the ground when the plants begin to show early spring growth. Another shrub that responds well to this treatment is the Tree Daisy (Montanoa grandiflora), from Mexico, which can grow up to ten feet high in one season. This annual treatment might seem drastic but the plants otherwise will become scraggly.

A good book on pruning is The American Horticultural Society’s huge “A-Z Encyclopedia of Garden Plants” (Revised edition, 2004), which briefly describes thirteen pruning categories and indicates which to use for each of 15,000 plants.

More

A thorough presentation on conserving water in the garden: “Guidelines for Managing Drought in the Urban Landscape,” was developed by Sonoma County Master Gardeners Susan Foley, Phyllis Turrill and Jerilynn Jenderseck, with input from Mimi Enright, Sonoma County Master Gardener Program Coordinator and Paul Vossen, UCCE Sonoma/ Marin Farm Advisor. (February 2014)

The following paragraphs, also from the Sonoma County Master Gardeners, provide brief recommendations for water conservation in the garden.

1. Compost, compost, compost! Add organic matter to the soil. If soil is sandy, the addition of organic matter allows the soil to hold more water. Organic matter also helps open up soil allowing roots to go deeper and find more water at lower depths if there is any. Higher soil nutrition helps plants produce better yields with the same amount of water. Avoid adding excessive amounts of nitrogen as this encourages lush leafy growth that requires more water to sustain.

2. Mulch, mulch, mulch! Mulch keeps soil cool, conserves moisture and reduces weeds. Use three to four inches on top of the soil. The larger the material size, the deeper layer you need to provide. Choose from straw, fallen leaves, hulls, shredded bark, grass clippings and newspaper. It is not advisable to use plastic sheeting as mulch because it deprives the soil of much-needed oxygen. Keep mulch two inches away from the base of the plant to avoid the possibility of rot. When hand watering, pull back mulch so that water goes directly into the soil.

3. Use a drip system. Learn about individual plant moisture needs and group plants that have the same need together on the same valve. If using in-line emitters in one-fourth inch tubing that use one-half gallon per hour per emitter and there is a length of ten feet with emitters spaced every foot, five gallons of water an hour is used on that section of tubing. Add up all drip lines to determine total water used. Install a timer. Install shut-off valves at the beginning of drip lines in order to turn them off when an area is fallow. Irrigate only as long as it takes to moisten the active root zone. Water, preferably, in the morning or in the cool hours of the evening so that soil stays evenly moist. Don’t forget the drip system once it is set up. Monitor and adjust it, as needed.

4. Be selective. Consider the water available to support crops through harvest, and grow only the amount and types of vegetables the family will consume. For example, plant two beds of vegetables instead of six; plant four tomatoes instead of ten. To get the most out of the water you apply, grow high yielding vegetables like beans, chard, mustard, eggplants, peppers, tomatoes, squash, quinoa and amaranth.

Do not grow crops that need consistent moisture. Examples include most brassicas (broccoli, cabbage, Brussels sprouts, kohlrabi, cauliflower and radishes), lettuce and other greens, beets, carrots and other root crops, celeriac, celery, leeks and onions. Avoid these unless a particular variety has been bred to need less water. Generally, cool season crops are not drought resistant and growing them during the heat of the summer requires lots of extra water to keep them cool.

Consider the following observations on which crops need the most water and when:

  • Some beans and sweet corn need considerable water to produce a good crop. Beans need water most when they are blooming and setting fruit.
  • Corn needs water most during tasseling, silking and ear development. Yield is directly related to quantities of water, nitrogen and spacing.
  • Peas need water most during pod filling.
  • Other vegetables, such as cucumbers and squash, and fruits, such as melons, need water most during flowering and fruiting.
  • Tomatoes, peppers and eggplant need water most during flowering and fruiting. (Note that after tomatoes set, they can do very well with reduced water).

After deciding what to grow, choose varieties that tolerate dry conditions. Look for the terms “drought-resistant” or “drought-tolerant” in seed catalogs or on plant labels (note that “heat-tolerant” refers to above ground air temperature and is not the same as drought-resistant or drought-tolerant). Even these varieties require water. Some water is needed to start seeds or establish a seedling, and to periodically irrigate the plant through the growing season. Selecting varieties that are described as “widely-adapted” in addition to drought-resistant and drought-tolerant also may be helpful.

5. Consider days to maturity. A crop needing fewer days to mature requires fewer irrigations before harvest (e.g., 62-day ‘Stupice’ vs. 85-day ‘Cherokee Purple’ tomato). Look for early-maturing or short-season varieties. Days to maturity will vary from one part of the country to another as well as from one microclimate to another.

6. Increase plant spacing. Spaced plants are not competing as much for water in the soil. Very deep, open soil or French intensive double dug beds allow vegetables to be planted closer together because the roots have more room to grow deeper and find water if it is present. Try increasing the spacing recommended in the SCMG “Vegetable Planting Summary,”iv by 50 percent or even doubling the spacing if you have room.

7. Eliminate weeds. Weeds compete for water. Be aggressive in removing them from growing areas.

8. Use light-weight row covers. Cover plants as a means to collect dew. Dew drops onto soil and keeps it moist. While using row covers can help prevent insect damage, look under the cover from time to time to monitor plant growth and check for unwanted insects trapped inside.

9. Use shade. Heat-sensitive vegetables can benefit from being planted where they receive some afternoon shade. Plant them underneath or behind taller plants or consider using shade cloth.

10. Use windbreaks. The moisture on leaf surfaces is dried by moving air, causing the plant to need more water. In coastal and other windy areas, windbreaks will help roots keep up with leaf demands.

11. Determine when it is time to water again. Use a soil moisture meter. Or squeeze the soil in your hand: if it sticks together, it is still moist; if it is crumbly and falls apart, it is time to water.

Notes from the Field

Gardening often resembles a random walk in which every turn in the garden reveals another opportunity to pursue or problem to solve. Today’s column follows that pattern with three current topics, unrelated except for being “on gardening.”

Sulfate of Ammonia

While clearing out “stuff” I found two 20-pound small bags of sulfate of ammonia fertilizer, which is 21% nitrogen, 24% sulfur and not much else.

Sulfate of ammonia is a long way from a complete fertilizer. It provides a rapid flush of growth and green color in foliage, and is often used on lawns. (I removed my lawn about twenty years ago.)

This special-purpose fertilizer also can be used to promote the growth of other plants, shrubs and trees in the garden, but it can over-stimulate plants, encourage tender foliage that insects particularly like, and in time acidify the soil. It should be used sparingly or not at all.

Another possible use of sulfate of ammonia would be to speed up decomposition in a compost pile: Washington State University researchers found that it would also lower pH (acidify) and raise available nitrogen. However, this is an inorganic salt, produced by combining ammonia with either sulfuric acid or gypsum and calcium carbonate. My garden is strictly organic, so I will either donate my stash to a lawn lover or dispose of it as toxic waste.

Seed & Bulb Exchange

Marina Tree & Garden Club will hold a Seed & Bulb Exchange at the Marina Farmer’s Market (at Reservation Road and Vista Del Camino) on Sunday, October 20th, 10:00–2:00.

Bring seeds, bulbs, tubers or root divisions to share or find something new for your own garden. The event welcomes both home-collected and commercial seeds, flowers, vegetables and California native plants.

Bring your offerings between 10:00 and 12:00. If possible, include the plant’s common or botanical name, blossom color and other information that gardeners like to know.

The Exchange is free and open to all, with or without items to share.

Bring a friend!

Swapping Flowering Vines

Years ago, I used half-inch copper tubing to build a trellis six inches wide and twenty feet high and attached it to an elevated deck. On this trellis I grew a common Woodbine Honeysuckle (Lonicera periclymenum), a woody twining climber. I became tired of this plant, but removing it was a daunting task.

Fortunately, a tireless student came to work in my garden and soon put the honeysuckle in the green waste. Then, at a Berkeley Botanical Garden sale, I found a Chilean Jasmine (Mandevilla laxa), a climber with beautiful, slightly fragrant blossoms and more than enough exotic appeal for this prominent trellis.

mandevilla_laxa_annie

This image of the Chilean Jasmine blossom is from Annie’s Annuals, a nursery in Richmond, California that supplies retail garden centers, and also offers plants by mail.

Change can be refreshing!

Teaming with Nutrients II

This column was planned to provide a closer look at Jeff Lowenfels’ new book, Teaming with Nutrients: The Organic Gardener’s Guide to Optimizing Plant Nutrition. I confess that I have read only the early chapters, due partly to other demands on my time and partly to the book’s demand for concentrated study.

In other words, Lowenfels gives this subject the scientific detail it deserves and that approach requires slow reading.

The book opens with chapters on The Plant Cell, Some Basic Chemistry and Botany for Plant Nutrition. It then proceeds to The Nutrients, Water Movement Through Plants, and Nutrient Movement Through Plants.

The four remaining chapters address The Molecules of Life, The Importance of Soil Testing, Factors Influencing Nutrient Availability, and What and When to Feed Plants.

I’m still reading, but my early assessment of the book has two parts. First, the text offers clear but not easy reading. Second, it provides basic science that is fundamental to successful gardening.

We can approach gardening as an aesthetic exercise, choosing and arranging plants to provide a pleasing display. If they succeed, we are delighted; if they do not, we either move them to spots that might be more hospitable, or discard them in favor of other trials.

If we approach gardening from the more scientific approach of Lowenfel’s Teaming with Nutrients (and his previous book, Teaming with Microbes) we can achieve very high degrees of success and plants with vigorous good health. And good health in plants means more beautiful foliage and blossoms, and stronger resistance to diseases and insect pests.

There is a middle ground. This is the territory of “green thumb gardeners” who succeed because they enjoy intuitive knowledge but don’t know why their plants flourish.

I respect green thumb gardeners and I am grateful for the occasions when my efforts qualify me to join their ranks temporarily.

But perhaps we prefer that our gardens hold a measure of mystery!

Most garden books emphasize gardening’s aesthetic aspects; Lowenfels’ book provides a rare example of plant science and nutrition from the perspective of a dedicated gardener.

Mark Your Calendar

As you consider adding this book to your reading list, consider these events for avid gardeners:

• Annual Iris Rhizome Sale I, Monterey Bay Iris Society, Saturday, August 3rd, (yes, today!), Deer Park Shopping Center, Aptos;

• Annual Rhizome Sale II, Monterey Bay Iris Society, Saturday, August 10th, Aptos Farmer’s Market at Cabrillo College, Aptos;

• Annual Show, Monterey Bay Dahlia Society, Saturday, August 31st, 1:00–5:00 and Sunday, September 1st, 10:00–4:00, Soquel High School, Soquel.

Teaming with Nutrients

Over two years ago, I reviewed an exceptional book on gardening in two of these columns. The book is Teaming with Microbes: The Organic Gardener’s Guide to the Soil Food Web, by Jeff Lowenfels and Wayne Lewis (Timber Press, 2010). That book uses readily accessible language to introduce gardeners to the microbial life that sustains healthy plants. It remains today an uncommonly scientific perspective on gardening and a valuable resource for all gardeners.

Now, the principal author of that book has released an equally valuable companion work: Teaming with Nutrients: The Organic Gardeners Guide to Optimizing Plant Nutrition (Timber Press, 2013). In this book, Lowenfels provides easily understood explanations of the chemistry, biology and botany involved in how nutrients get to plants, and how they contribute to the plant’s health and vigorous growth.

Common knowledge indicates that nitrogen is responsible for strong stem and foliage growth, phosphorus aids in healthy root growth and flower and seed production, and potassium is responsible for improving overall health and disease resistance.

Many gardeners employ a fairly rudimentary approach to plant nutrition, and often adopt one of the following major perspectives on the subject.

The Balanced Fertilizer Group doses all plants with a chemical fertilizer with equal parts of nitrogen, phosphorus and potassium, represented by the symbols N, P and K, e.g., a fertilizer labeled “10–10–10.”

The Customized Fertilizer Group uses chemical fertilizers that have varying percentages of these most important nutrients, depending on the cultivation objectives. For example, Osmocote’s Indoor/Outdoor Fertilizer, labeled 19–6–12, focuses on strong top growth and overall health, and less on root growth.

Both of these groups use more nitrogen than their plants really need, while unintentionally delivering excess nutrients that wash into waterways and harm aquatic ecosystems.

The Organic Fertilizer Group relies on fertilizers composed of organic plant or animal matter. These fertilizers include commercial products, manures and plant materials that a gardener composts in his/her own garden. These fertilizers also could be described in terms of N-P-K ratios, but compared to chemical fertilizers they act more slowly and over longer periods, and are friendlier to the environment.

The No-Fertilizer Group includes gardeners who add nothing to their gardens in the belief that plants will grow in the same soil year after year without depleting the nutrients. This is an error, as the garden’s declining performance demonstrates eventually.

In this book, Lowenfels offers deeper understanding of the major and minor plant nutrients and delivers the necessary science in a conversational style that most gardeners will appreciate.

Next week’s column will review Teaming with Nutrients in more detail and (no surprise) recommend reading this book as an investment in your long-term success in gardening.