COLUMBUS, Ohio -- When using heavy machinery on cropland under potential compaction situations, farmers may get better yields by practicing continuous no-till than with annual deep tillage.
According to results from a six-year Ohio State University compaction study at the Northwest Agricultural Research Station near Hoytville, land in continuous no-till showed less effect from intentional compaction than soil that was deep tilled (subsoiled) each fall.
Researchers compacted corn/soybean rotation plots in the fall of 2002 and 2005 using a 20 ton/axle, 600-bushel grain cart. Averaged over six years, corn yields were reduced by 15 percent on subsoiled plots, as opposed to a 9 percent reduction in no-till fields. For soybeans, yields on subsoiled plots were down 24 percent, compared to a 13 percent yield drop under no-till.
"We think continuous no-till performed better because of better soil structure," said Randall Reeder, an Ohio State University Extension agricultural engineer. "Good no-till soils are firm, with natural channels for root growth and movement of water and air. Tillage tends to destroy that soil structure."
Previous compaction research at the same site gave results more favorable to subsoiling, but there was a key difference. Once annual subsoiling began on the compacted plots, there was no additional intentional compaction for 12 years. In that situation, subsoiling gave consistently higher corn and soybean yields, compared to shallow chisel plowing.
When the research practices were changed in 2002 to include intentional compaction every three years, and continuous no-till replaced chisel plowing, the benefit of deep tillage disappeared, said Reeder.
"The current research is much closer to the real world because the average square foot of soil on farms with big equipment is going to be driven on at least every three or four years," said Reeder, who also holds a research appointment with the Ohio Agricultural Research and Development Center.
Soil moisture plays a big role in compaction, said Reeder, and as spring progresses and Ohio receives more rain, soil moisture may be the factor in deciding when to start planting.
"Wet soil compacts deeper than dry soil," said Reeder. "Typically in late April and early May, there is only one day out of three that is dry enough to plant."
Reeder said that under compacted soils, farmers could easily lose 5 percent to 10 percent of their corn or soybean yields. So, how do farmers know if their fields are compacted?
"Most farmers don't know, because they don't have any non-compacted area for comparison," said Reeder. "But there is a way to get around this mystery. It's called controlled traffic. With controlled traffic, a grower never has to be concerned about whether or not the soil is susceptible to compaction."
Controlled traffic is a method whereby all farm equipment is the same width (or multiples of that width) and traffic is confined to specific paths year after year.
Without switching to controlled traffic, there are other ways growers can help minimize compaction:
• Run tires at the correct pressure for the load. "Many farm tires are overinflated, which reduces the tire footprint, increasing compaction," said Reeder. "Many farmers can easily reduce tire pressure and it won't cost them anything." Over inflation also reduces traction.
• Remove excess weights that make a tractor heavier than necessary. Extra ballast needed for a tillage operation could be removed when pulling a planter.
• Add more tires, or switch to bigger tires or rubber tracks. The more rubber that comes into contact with the ground, the less pressure on the soil.
• Consider improving surface and subsurface drainage. A good drainage system helps the soil dry out faster, reducing the potential for soil compaction.
Compaction can have a number of impacts on the soil and the plants growing in it. Compaction destroys the soil structure and causes erosion by keeping water out. It prevents plant roots from penetrating deep into the soil, and traps carbon dioxide while preventing oxygen from reaching plant roots. The result suffocates the plant either killing the plant or impacting yield performance.
Continuous no-till may be one practice to help minimize the negative effects, said Reeder.