Conservation-tillage, says University of Georgia small grains specialist Dewey Lee, could almost count as a religion — sometimes you have to take it on faith.
About 30 to 35 percent of Georgia's corn growers now practice some form of conservation-tillage, and they're “taking it on faith,” based on research and experience, says Lee.
“The amount of cover we're able to produce prior to corn varies from year to year depending on the type of cover we use or what we're planting behind corn,” says Lee. “And the type of cover varies from year to year, whether it's all residue, wheat or rye.”
Positive experiences by growers with conservation-tillage corn also vary from crop to crop, he says. “Some of the benefits are relatively small in the long-term. And as a grower, you often have to react in the short-term because of cash and returns on your inputs. So we don't necessarily see the long-term benefits of conservation-tillage,” says Lee.
Most farmers, he adds, want to know if the benefits are going to put cash in their pockets, and if they can be good stewards of the land for the next generation.
Some studies and research can be confusing as to the specific benefits of conservation-tillage, says Lee. “As for true cost savings, we can show you that there are some cost benefits to conservation-tillage. But what about better yields? Maybe or maybe not. But there are more efficient yields with conservation-tillage,” he says.
In Georgia, the basic rotation consists of cotton peanuts, corn and cattle, says Lee. “These enterprises all interact together to sometimes increase or decrease the degree of benefits you'll receive from conservation-tillage,” he says.
The kind of cover crop can affect a conservation-tillage corn crop, he says, whether it is black oats, rye, wheat or old residue. Research has shown poorer yields in corn behind wheat than with other crops such as cotton.
“A lot of growers use wheat because the seed is cheaper. It's important to address exactly what cover we're going to use. My preference as a cover for corn would be rye because of the amount of residue we can get,” says Lee.
Research also has looked at the effects of reduced-tillage in corn production, he says. “When we look at straight no-till, there's a significant difference in response to tillage, and we expect that in corn. When we look at strip-tillage or slit-tillage, there's a slight advantage to conservation-tillage. But what is the cost advantage? Part of it is reduced inputs.
“Whenever you as a grower are talking to someone in research or Extension, and they use the word ‘no-till,’ make sure you understand exactly what they mean. There are differences because they might be talking about slit-till with no-surface-tillage. In a true no-till, no in-row subsoiling is taking place,” he says.
Turning to the effect of row-width, Lee says most producers in Georgia will be planting corn either in twin rows or 36-inch rows. “There's really no difference in the twin-row and 36-inch row patterns. It's your ability to manage and get good seed-to-soil contact — that's the biggest difference. But when you look at a 30-inch row, which is slightly narrower, then you start to move up that yield curve. You're casting more light, and you get an earlier benefit from your fertilizer application because your plant distribution is different than in a 36-inch row pattern.”
There's also a significant change in 20-inch row corn, although the plant population — 30,000 per acre under irrigation — remains the same, he says. “The difference we see in the yield line is the ability of the grower to obtain a stand in a conservation-tillage and residue system. The seed needs to hit the ground and the soil surface — it doesn't need to sit on top of that residue. When you look at conservation-tillage, most of the problem in corn production is associated with plant establishment and plant stand and the ability to make sure the seed emerges at the same time.”
Managing corn in a conservation-tillage environment is different from managing in a conventional environment, says Lee.
“Most of the value in conservation-tillage corn appears to be in production efficiency and not in additional yield. But what does it take to extract that production efficiency? Certainly there's a savings in fuel and water. But maximizing the benefit of a cover crop means planting that cover in September or October rather than in November or December. This will allow you to obtain a greater degree of residue which will improve your water infiltration.”
Lee makes the following recommendations for making a conservation-tillage system work in corn:
Plant rye as a cover crop. It provides the greatest amount of residue in the quickest time, and it has the deepest root profile, which extracts more nutrients earlier in the season.
Consider disease-resistant cultivars, as there tends to be a greater disease presence in conservation-tillage corn.
Manage residue to obtain good seed-to-soil contact and a uniform plant stand.
Achieve a good plant population. This is especially important in irrigated corn, but also important in dryland production.
Move the residue to the side with your equipment. Don't push residue into the seed slot. This will harm your ability to get a good stand and ultimately hurt your yields.
Disrupt your hardpan. Research has shown a significant yield loss in corn in a straight no-till environment in sandy loam soils such as those found in south Georgia. Disrupt the hardpan with good in-row subsoiling.
Manage all of your inputs to obtain yield goals. Good, strong management practices are the same in conservation-tillage as in conventional-tillage.