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Biochar: Prepping it for Soil

Biochar can benefit your soil, but only if properly prepared prior to application. In November 2007, scientists at the USDA National Laboratory for Agricul­ture and the environment (NLAE) in Ames, Iowa, began multi-year field trials to assess the effects of biochar on crop productivity and soil quality. Scientists amended almost 8 acres with biochar made from hardwood. Twelve plots re­ceived 4 tons per acre; 12 were treated with 8 tons per acre.

Author David Yarrow helps install a biochar test plot at Subterra in Kansas.

They found no significant difference in the three-year average grain yield from either treatment. Other USDA field and laboratory studies in Idaho, Kentucky, Minnesota, South Carolina and Texas showed hardwood biochar can improve soil structure and increase sandy soils’ ability to retain water. But soil fertility response was more variable.

USDA scientists violated four key principles for biochar use: 1) bulk char, in one large load 2) raw, uncharged char 3) sterile, uninoculated char, with only a tad of microbial life 4) synthetic salt fertilizer, tillage and other antibiotic practices.

After all, soil may get 25 or more inches of rain a year, but not all at once in a single event. Biochar, like water, is best added in a series of small doses so soil has adequate time to distribute and digest it. We already know from research in the Amazon that dumping five, 10, even 20 tons of raw char all at once into poor soil retards plant growth for one year and maybe two. But after that, plants erupt in impressive, vigorous growth.

But a dip in yield isn’t acceptable for production agriculture. Farmers can’t wait a year or two to harvest a profit­able crop. Professional growers need fast response and strong stimulus to growth. Economics and handling logistics require convenience and low cost, with vigorous growth from minimal applied material.

Fortunately, we are learning how to prepare char for optimum results in soil and on crops. Biochar research in America is hardly 10 years old, but solid research shows that properly prepared, intelligently applied biochar has dramatic effects on soil structure and plant growth at as little as 500 pounds per acre.

To prepare biochar for optimum effec­tive use in soil, there are four fundamen­tal steps: moisten, mineralize, micronize and microbial inoculation. Continue Reading →