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Joanne Thiessen Martens and Martin Entz
Can organic crop production and no-till crop production ever come together? While at first it may seem like an unlikely union, there is growing interest in developing organic no-till crop production systems that bring together the benefits of both systems.
The main beneficiary of organic no-till is the soil, which is a farm’s most important resource. A healthy soil system is critical for profitable and sustainable organic farming and the basis of a healthy soil system is soil organic matter. It is soil organic matter that turns clay, silt, and sand particles into something that is able to support life.
Soil is “built” naturally as organic matter is added to the soil. The soil-building process can be sped up by using diverse crop rotations, planting cover crops, and adding manure to soils, all of which are common practices on organic farms.
At the other end of the equation, soil-building also involves protecting the soil organic matter that already exists. Soil organic matter breaks down naturally over time, releasing nutrients for plant uptake. However, accelerating the break-down process can deplete the soil of organic matter. Tillage operations accelerate this process by physically damaging soil organic matter and increasing the potential for soil erosion.
There has been some debate over which farming system does a better job of building soil – organic or no-till. Proponents of no-till crop production claim that eliminating tillage protects soil organic matter from mechanical damage and erosion, while proponents of organic crop production claim that addition of organic matter through green manures, animal manures, and good crop rotation more than compensates for any damage done through tillage. Regardless of which system is “better”, the truth is that both approaches have merit, and that bringing the two closer together will have positive effects on soil health in both systems.
Eliminating tillage from organic crop production is a lofty ideal. In reality, tillage is one of the organic farmer’s most important tools for weed control and green manure termination and incorporation. Tillage has, however, been overused at times, and there are certainly opportunities to reduce tillage in organic crop production. Use of green manures during the fallow phase, rather than traditional black summerfallow, is one practice that has already allowed for considerable reduction in the amount of tillage carried out on organic farms on the prairies.
According to researchers at the Rodale Institute, a functional organic no-till system is based on effective use of cover crops and green manures. Since green manures are generally terminated and incorporated through tillage, alternative methods of managing these crops will help to reduce or eliminate tillage on organic farms.
One such method is the use of a blade roller, also called a crimper roller, to terminate green manures. Here in the Department of Plant Science at the University of Manitoba, we began experimenting with a blade roller in the summer of 2007. Plans were obtained from the Rodale Institute for a roller developed by Cedarwood Meadow Farm in Pennsylvania, and Mr. Glen Kippen at the Carman Research Farm built us our very own blade roller.
The roller consists of a drum with protruding blades attached lengthwise along the drum (see photo). The drum is filled with water for weight (we also used additional weights on top of the roller), and pulled on a three-point hitch. As the roller is pulled through the green manure crop, the blades crimp or sometimes even cut through the plant stems and the roller flattens the crop to the ground.
This summer, we did some preliminary trials evaluating the effectiveness of the roller at killing the green manure crop. An oat/pea green manure crop was rolled in late July. Pea and oat stems were “crimped” by the blades every 20 cm or so, and the crop showed signs of wilting within about 15 minutes of rolling. One week later, the rolled oat/pea crop was predominantly dead (see photo), although later in summer there was some pea regrowth. Some of the plots were rolled a second time.
In a second trial, green manure crops (lentil, oat/pea, chickling vetch, fababean, hairy vetch) were terminated with various combinations of rolling and tillage to see if an optimum number of rolling operations and tillage operations could be determined. Preliminary results indicate that some crops are more susceptible to rolling than others, although rolling did kill all crops tested. Rolling crops first and tilling later resulted in more erosion resistant soil cover going into winter.
A number of questions arise regarding the effectiveness of the crop roller and the effect that it could have on various management issues in organic crop production:
In the new year, we will be welcoming a graduate student who will study the roller in greater depth. We are looking forward to exploring this exciting opportunity to improve green manure management practices on organic farms and to bring organic and no-till systems closer together.
To learn more about our experience with the crop roller and to see
it in action, watch a video clip about the roller at www.umanitoba.ca/outreach/naturalagriculture/video/roller.html.
© 2012, Organic Agriculture Centre of Canada (OACC)