COLUMBUS, Ohio - To till or not to till? Balancing conservation with productivity makes for a weighty decision, says an Ohio State University agronomist.
Tillage is a practice whereby fields are plowed to loosen the soil and bury crop residue before seeding the following season's crop. In no-tillage, crop residue is left undisturbed and seeds are placed directly in untilled soil.
No-tillage is becoming a more popular agricultural practice. According to the Conservation Technology Information Center (CTIC), no-till adoption in the United States has increased more than 200 percent since 1990 from nearly 17 million acres to over 51 million acres. In a 2000 CTIC tillage system usage survey, 60 percent of Ohio's soybean crop and 24 percent of the corn crop was planted using no-till.
"There are two main reasons why farmers should practice no-till: economics and soil conservation," said Jim Beuerlein. "Tillage production can run anywhere from $15 on the low-end up to $30-$40 per acre and there's often not enough yield generated to make tillage profitable."
According to Ohio State research, a farmer would have to increase his corn yields an average of 8.4 bushels per acre, soybean yields 5.6 bushels per acre and wheat yields 3.4 bushels per acre to recoup the tillage costs, depending on the type of equipment used.
Tilling also causes soil erosion, an environmental problem that no-tillage reduces. "No-tillage usually reduces erosion up to 90 percent compared to tillage practices," said Beuerlein. No-tillage also conserves and improves water quality, and stores more carbon in the soil than plowed land. Hence it improves soil quality and helps reduce carbon inputs to the atmosphere that are thought to be the cause of global warming.
Despite the conservation benefits, no-tillage does have its disadvantages depending on the crop and soil type.
"Poorly drained soils, such as clay soils, tend to get tilled more because they don't dry out as fast in the spring. No-till on poorly drained soils is definitely a problem," said Beuerlein. Poorly drained soils are much colder and wetter in the spring, causing slowed growth, and disease problems for crops that are planted in no-tillage fields.
"How all this affects your crop depends on the type of crop planted. Corn isn't no-tilled a lot because it's planted in early spring. Soybeans tend to dodge those problems because they get planted later on when the soil is much warmer," said Beuerlein. "No-tillage is actually beneficial for wheat in that it practically eliminates heaving, where the plants get pushed out of the ground due to freezing and thawing of the soil in the spring. No-tilled soil also has a greater bulk density and helps the root system anchor the wheat plant a lot better."
Beuerlein said there are some situations were tillage should be considered:
* When inadequate soil drainage leads to serious yield loss due to root rot diseases, poor stand establishment or late planting.
* To bury crop residue and thus reduce pathogen survival that can infect a following season's crop.
* To use as a prelude to land leveling, rock removal and for the incorporation of soil amendments such as lime or very high rates of fertilizer.
* To mitigate compacted soil layers or zones that interfere with water movement into and through the soil which may delay planting, harvesting and other field operations.
* To destroy crop residues that harbor insects that can interfere with succeeding crops.
Tillage and no-tillage practices have their pros and cons and farmers should weigh them all when choosing which technique best suits their farmland and their pocketbook, said Beuerlein.