"No-till" or "low-till" cropping systems - increasingly common in large scale traditional agriculture - are superior because they consume less energy, build soil organic matter over time, sequester carbon, and greatly reduce soil and nutrient loss. (The old style moldboard plow behind the mule was actually terrible for the land: with soils deeply turned and broken up with several passes, leading to rapid soil loss and eventually productivity loss for the farm. Such primitive farming practices were a contributing factor to the Dust Bowl.)
Green Products Made With Crop Residues Can Compromise Long Range Food Productivity.
What happens when you scrape up most, or all, of the non-food portions of a crop, and make cellulosic ethanol or kitchen counter tops with it? Soil erodes at a faster rate and, over time, the organic content falls, leading to lower productivity. The latter issue is well described in a report by Washington State University, USDA-Agricultural Research Service soil scientist, Ann Kennedy.
Kennedy, whose current research is examining the composition of cereal crop residues and the amount of residue needed to maintain soil quality, said that in direct-seed or one- pass tillage systems at least a ton of residue per acre per year is needed to build soil organic matter over time. In these minimum tillage systems, the intact and slowly decomposing roots also add to organic matter. In fields with multiple tillage passes, every bit of residue is needed and even then, organic matter may not increase.So...is wheat straw board a "green product". How about ethanol made from corn stover? Among other things, the answer depends on whether the demand created by a crop residue based product resulted in a significant reduction in post-harvest soil cover. It's a situational question. For an extensive discussion of the "caveats" have a look at this USDA white paper, Crop Residue Removal For Biomass Energy Production: Effects On Soils And Recommendations (streaming image version). Also available as a pdf download here.
What of organic farming systems that use the moldboard plow to turn soil completely? Do they cause long term loss of soil organic matter under certain condition? We will have to defer to the experts on that question.
One thing is certain. Farmers have their hands full stewarding the soils while producing our food. If we also require them to help build our kitchen cabinets and fuel our vehicles, something is going to fall by the wayside, and it's probably going to be our nation's agricultural productivity. It's a high risk public policy to push that on farmers. Calling something green does not make it better without a full life cycle risk management evaluation.
It would be interesting to hear what organic farmers have to say about this issue.
Via::WSU Today, Protecting the soil, Straw residue too valuable for biofuel. Image credit:WSU Today.
For more information about soil loss impacts:
Plowing's Dark Secret
Organic Farming More Than Competitive
Shhhh, We've Got a Secret: Soil Solves Global Warming, Part 1 ...