Some farmers who think about converting to the no-till planting system are concerned there will be a drop in crop yields either in the short or even term.

Truth is, there may be, says a Penn State University agronomist, but it won't last.

A short-term loss may be noticeable during a period of years of a transition phase, often referred to as "yield drag," says John Rowehl. He says there is some debate about how much this yield drag amounts to, how long it lasts or even if it does in fact occur.

"When no-till was new and farmers lost yield, it could often have resulted from not being able to get seed planted at the proper depth or adequately covered, and they simply did not have a normal plant stand," Rowehl says. "Improvements in planter design and operator knowledge have reduced this problem, yet the perception of yield reduction during transition to no-till is generally an expectation.

"Three to 5 years is commonly agreed upon in such discussions, although it can be greater or less."

Some farmers will say there does not have to be any loss of crop yield if the transition to no-till is done the right way, Rowehl adds. Should we not expect that there would be differences depending on the condition of the soil when this transition begins? Might it depend on where in the crop-rotation cycle that the change to no-till begins?

"Corn is usually the crop first planted, since the farm's row crop planter is usually easiest to get set up for no-till," Rowehl says. "One strategy for farms where a hay crop is in the cropping rotation is to start no-till corn at the end the life of the hay stand, when the soil has already not been tilled for a few years.

"The soil has already begun to develop the characteristics seen in long-term no-till. In this case, complete kill of the existing hay crop is critical."

But for farms that do not grow hay crops, Rowehl and Penn State researchers are questioning whether cover crops can help speed the transition, according to a 4-year study.

Seven different grain-crop systems were compared. Three systems that had a simple corn-soybean rotation compared a tilled system; no-till; and no-till with a rye cover crop.

In the first year, there was no yield loss for the soybeans from going to no-till. For the following year, when corn was the next crop, there was no difference in yield from any of the systems.

By the third year, Rowehl says researchers began to see that the soybeans in no-till were beginning to show a higher yield over the tilled system. In the fourth year, tilled corn was not lower than no-till corn but was lower in yield than no-till corn that had had rye cover crops used each year.

"In two nonrotation systems, tilled corn and no-till corn had comparable yields in the first year, although it takes loyal faith in statistical analysis to be convinced of that," Rowehl says. "From then on, corn yields were the same. However, in some years the system with a rye cover crop gave some yield advantage.

"From this study, we would expect that there might be some risk of yield reduction when starting a no-till system with corn. If we do, we can expect that after the first year, yields will be comparable.

"If we begin no-till with soybeans and rotate to corn the second year, we could expect that there would be very little chance of yield loss and perhaps even some improvement. Use of a rye cover crop seems to give an additional advantage to this as well."