Wednesday, September 29, 2010

BIO-TILLAGE, WHAT ON EARTH IS THAT? (Extension News Release)

Everyone is familiar with that lovely piece of field equipment being pulled behind the tractor, inverting the soil as it goes. Tillage is used for many reasons in agriculture. Inverting the soil kills weeds, buries crop residues to hasten their breakdown to stop disease cycles, and tillage can leave a clean flat surface that is easy to plant into. I’ve done my fair share of tillage, and, boy, was it fun. There is nothing more productive feeling on the farm than spending an afternoon flipping the soil and looking at a clean field when you are done.

There is a negative side associated with tillage. It is an expensive undertaking. Combine large equipment with high diesel prices and tillage can sure make an impact on your wallet. It also takes time. Tillage is usually accomplished at 4 mph. Compare that to a sprayer traveling in the range of 7 to 15 mph that covers a wider swath width. With advancements in no-till planting equipment, crop rotations, and a realization of how much soil is lost as a result of tillage, that practice seems to be on its way out. So what’s this bio-tillage that seems to be the newest rage?

Well, it’s a simple concept. Traffic on a field causes soil compaction. As we plant, spray, till, harvest and even walk in the field, we compress the soil. Compaction occurs when the mineral component of soil (what we usually call dirt) is pushed together and decreases air and water space in the soil. In no-till we rely on organic matter in the soil to act as a spring allowing the mineral particles to compress but keep their structure so they rebound to their original position. But what if the force we put on the soil is too much and compaction occurs? What can we do in a no-till situation?

This is where bio-tillage can help. Bio-tillage relies on crops that are able to send roots through compacted soils that our corn and soybeans might not be able to penetrate. The root channels that remain after the tillage crops die are often utilized by the following corn, soybean or wheat crops. The question always comes up, “Do these crops actually till the soil?”

After reading through articles in periodicals like the Soil Science Society of America Journal and even Pesquisa Agropecu├íria Brasileira, yes, that’s right, a Brazilian journal in Portuguese, “They do most of the time” is my answer.

Depending on soil conditions adding cover crops to a rotation can reduce soil bulk density in compacted areas. Soil bulk density is the measure of solids in the soil compared to pore spaces for air and water. As soil bulk density increases we lose pore spaces for air and water and generally see a decrease in root growth. The addition of grass or broadleaf cover crops to a rotation helps decrease bulk density compared to leaving the area fallow. We also see a longer lasting decrease in bulk density compared to conventional tillage. Is there a difference in which cover crop we use? Well, that is a harder question to answer. Some research says broadleaf crops are better at breaking through deeper tillage than grasses; some research says they are the same. But all the research I’ve found agrees that growing roots making channels in the soil is better than nothing or even tillage. There are some products marketed specifically for bio-tillage. Are they worth the added cost? For now I’d say no. I can’t find any research in a peer reviewed scholarly journal that states product A is better than its regular old competitors that aren’t marketed for tillage. Interested in this concept? Give me a call. I have some research opportunities you can take part in. Also, I’m in a rush to put out plots that include radishes with wheat at planting to increase yields through nutrient recycling. If you have some wheat ground and want to see if you can increase your yields by adding 2 pounds of radish seed per acre, contact Justin Petrosino at the OSU Extension office here in Darke County at 548-5215.

Justin Petrosino, ANR Extension Educator, OSU Extension, Darke County

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