   Using Biochar in the Garden - October 1, 2014 Jeff Schalau, Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County Biochar is an increasingly popular soil amendment. When I last wrote about biochar in 2009, there was little scientific information in the popular garden literature. But earlier this year, Washington State University Extension Specialist , Dr. Linda Chalker-Scott, conducted a scientific literature review of biochar with some very encouraging findings. Below are the highlights and her WSU Extension Fact Sheet FS147E (see link below) about biochar. Here, I have summarized a few of the higher points of this work. Biochar is a fine-grained charcoal left behind after pyrolysis of wood, crop residues, livestock manures, and other organic material used in alternative fuel production. Pyrolysis is the high temperature (500oC or 932oF) processing of organic materials in the absence of oxygen. Biofuel researchers initially regarded biochar as a waste product. However, upon further investigation scientists found that biochar is so slow to decompose that scientists widely consider it to be a long-term repository for stored carbon which can mitigate effects of climate change. Researchers have shown that biochar is similar to activated charcoal which can be used successfully to treat sewage and waste water. It is also exceptionally well suited for restoring degraded soils, such as those found near mining sites, because it tightly binds toxic heavy metals and neutralizes unnaturally acidic soils. When heated slowly for several hours it produces a lightweight, fine-textured, negatively charged biochar. Contrary to the column I wrote in 2009, biochar cannot be produced effectively at home because it is difficult to reach effective temperatures. According to Dr. Chalker-Scott, “The science behind biochar is complex: there are many variables associated with both making and using biochar.” Each material used to make it gives it differing properties. Biochar made from straw is different than those made from coconut husks, yard waste, or wooden pallets. Also, the temperature at which it they are charred will create varying chemical and physical properties. In addition, biochar effectiveness is highly dependent on soil characteristics, such as texture, organic matter content, and mineral nutrient levels present. Because biochar can remain intact for hundreds of years, it has the potential to permanently change soil characteristics. Biochar is porous and improves aeration of poorly drained or compacted soils. It can also increase water-holding capacity of fast-draining, sandy soils. Biochar’s micropores provide spaces for beneficial bacteria and fungi to colonize and take refuge therefore hiding them from foraging protozoa such as amoebas. Plant pathogenic (plant harming) bacteria also decrease when biochar is added. Earthworm populations, however, often decline in biochar-amended soils, possibly due to pH changes or dehydration. Remember, most of the earthworms present in North America today were introduced by the early settlers (more on this is linked below). Why use biochar? In studies, crops grown in biochar-amended soil have consistently shown increased growth. This may be due to improved nutrient and water availability and an increased number of beneficial microbes. Other biochar benefits include improved drought tolerance and greater resistance to root and leaf diseases. At the same time, gardeners should be careful when using biochar. Application of too much biochar can injure plants, possibly by increasing soil alkalinity past the plant’s tolerance level. Also, applying biochar to soils rich in organic matter can temporarily reduce nitrogen levels because microbes will out-compete plants for this nutrient (a quick guide to diagnosing nutrient deficiencies is linked below). There are good reasons to be excited about the possible benefits of biochar in home gardens. A solid body of research is available that describes the benefits of adding biochar to crops, soils, and soil microorganisms. If you want to try biochar in your garden, be sure to use only a commercially produced biochar with well-defined characteristics. If you decide to use biochar, monitor your plants in the first few months for signs of nitrogen deficiency. As always, small experiments in your garden may help determine if biochar could benefit your soils. The linked article by Dr. Linda Chalker-Scott summarizes the benefits, drawbacks, and best uses for biochar. In closing, I invite readers with biochar experience to share their results with me through the feedback form on the Backyard Gardener website. Follow the Backyard Gardener on Twitter – use the link on the BYG website. If you have other gardening questions, call the Master Gardener help line in the Camp Verde office at 928-554-8999 Ext. 3 or e-mail us at verdevalleymg@gmail.com and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. Additional Resources Biochar: A Home Gardener's Primer Dr. Linda Chalker-Scott, Washington State University Extension Fact Sheet FS147E cru.cahe.wsu.edu/CEPublications/FS147E/FS147E.pdf Earthworm Invaders Ecosystems on the Edge, Smithsonian Environmental Researchh Center ecosystems.serc.si.edu/earthworm-invaders/ Diagnosing Nutrient Deficiencies Quick-Reference Shawna Loper, University of Arizona Cooperative Extension Fact Sheet AZ1609 extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1609.pdf  |