More soybean farmers are using no-till, and this practice, added to the stronger, denser corn stalks that are the standard now, means growers are facing excessive residue issues. Leaving some corn residue on the fields provides important soil conservation benefits, but heavy amounts can bring disease risk and other stresses down on newly planted soybeans. Using no-till in more than one crop in the rotation can also stress seedlings through the creation of “tight” soil.
Luckily, there is a way to help protect soybean yields. “Using minimum-till provides the benefits of tillage but avoids the negative aspects of no-till,” says Horst Bohner, soybean specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).
No-till is believed to add organic matter to the soil and build soil structure, whereas plowing reduces it over time. On the other hand, a small amount of tillage can lower slug populations and warm the soil for planting, leading to higher yields.
Within the last decade, new “vertical tillage” and minimum tillage implements have been introduced to help manage heavy corn residue. Among the many options available in the Canadian marketplace are the Salford RTS, Landoll VT Plus, the Amazone Catros, International Turbo 330, Gregoire Besson Disc 0 Mix and the Case IH 330. Sunflower released its 6630 VT in fall 2010 and has sold 30 units in Ontario so far. “We can’t get them in fast enough,” says product specialist Steve Hosking. “Our niche is the saber blade and an aggressive configuration, which allows us to perform better at slower speeds equalling less maintenance, horsepower and fuel consumption.”
In 2003, Salford Farm Machinery in Salford, Ontario, released its RTS vertical tillage unit, with individual, spring-loaded shanks that carry coulters. “The standard RTS is equipped with fluted coulters, which enter the ground 1.5 to 3 inches deep at 90 degrees,” says Salford’s national sales manager Jim Boak. “This prevents the creation of ‘secondary density layers’ that using a cultivator can cause, and also avoids ‘side-wall smear’ like the angled blades of a disc.”
The RTS operates most effectively at high speeds (8 to 12 mph). Salford also offers more aggressive vertical tillage models such as the RTS Extreme, which features two rows of shallow concave blades mounted at the front of the unit.
Minimum tillage study
Since 2005, Bohner has studied whether minimal tillage can help to increase yields for no-till soybeans, or whether more aggressive tillage is necessary to maximize yields. The studies were supported by the Agricultural Adaptation Council (AAC), the Grain Farmers of Ontario and the Ontario Soil and Crop Improvement Association. The first part of the study from 2005 to 2008 used an RTS unit followed by seeding with a John Deere no-till drill. “The average yield gain over the three years of the study was only 1.8 bu/ac,” notes Bohner. “This is not enough of an increase to warrant the use of minimum tillage in every case when the costs of time, diesel and equipment maintenance are factored in. But in cases where the yield response was higher (heavy soil types, poor crop rotation, and extremely heavy residue), it starts to make sense.”
In 2010, Bohner ran tillage trials near Lucan and Bornholm that showed minimum tillage does impact yield positively in heavy corn residues, but says the results have to be examined in light of conditions seen during the 2010 growing season. “It was not a particularly good year to show the advantages of using some tillage versus none,” he says. “The spring was not overly wet or cold so the soybeans got off to a good start. Overall, the growing season was exceptional, with great weather, no significant insect or disease pressure and very high yields.”
He adds, “One of the reasons that tillage proved to have a positive impact on soybean yields at these locations may be that these trials were planted relatively early.”
Bohner found the RTS Extreme prototype to have a greater impact than the RTS. He says these results show that there is promise for using minimal tillage units to increase yields, but that “it may take more tillage than one-pass vertical tillage to significantly change yields.”
At the Lucan location, Bohner also ran a treatment in which corn stalks were removed with a hay rake before no-till soybean planting. “The results were very significant – a yield gain of over 7 bu/ac,” he notes.
This huge response to residue removal led to Bohner setting up more trials in 2011. They involved testing 10 different tillage types and three rates of corn stalk removal for a total of 30 different treatments. These trials also focus on the timing of the tillage (fall, spring, and a combination of both) on varying soil types. “Although no definitive conclusions can be made at this point from these trials, it seems that some sort of corn residue management in a heavy residue situation is a wise move to protect soybean yields,” Bohner says.
