Answer: True. “Surface compaction causes large yield reductions that are relatively short-lived,” Duiker says. “Deep compaction causes less yield reduction, but it is very long lasting (c).”

Research at Ohio State University found that corn and soybean yield losses persisted for more than a decade after the soil was compacted, says Randall Reeder Ohio State University ag engineer emeritus, even though no further compaction occurred. Average yields (a) were about 10% lower than on non-compacted soil. The effects on topsoil compaction gradually abated, but compaction in the subsoil (b) continued to reduce yields, even after 12 years.

“Lower subsoil compaction is, practically speaking, permanent,” Duiker says, “and should therefore be avoided by all means, whereas topsoil compaction and upper subsoil compaction are temporary and should be limited as much as possible.”

Left: Controlled traffic matches implement widths to align all field traffic into lanes, limiting compaction to just 17%, compared to 85-100% of a field compacted in conventional operations. Right: A controlled-traffic field has much lower overall soil compaction (pink line) than a conventionally farmed field (blue line), as measured by soil penetrometer resistance. The traffic lanes, (yellow line) contain the compaction to spare the growing zones.

An internal study from 1988 to 2002 found that the effects of compaction in the topsoil and upper part of the subsoil abate after five to 10 years if there is no further compaction. But deep subsoil compaction persists.