But adding to this rotation a few years of sod, a soil holder, could bring the average loss to within 7 tons per acre per year. This a reasonable outcome that would meet highly erodible land compliance requirements on most Kentucky soils, Smallwood said.

There are different levels, or classes, of highly erodible land. With conventionally-tilled tobacco on the least erodible class, erosion control practices include cover crops, strip-cropping or permanent grass strips, which might be all that is needed. 

On the more highly erodible fields, rotation with sod or no-till crops is the key.

“On many upland fields in the burley and dark tobacco regions, rotations with three to five years of sod for every one year of tobacco may be required,” said Paul Denton, burley tobacco specialist with University of Tennessee and University of Kentucky.

No-till or strip-till can help tobacco farmers stay in conservation compliance.

“In the early 1990s this was the way many cotton and grain crop producers were able to stay in compliance with minimal effects on their operations.  At that time conservation-tillage was not seen as a viable alternative for tobacco, but advances in weed control in tobacco have changed that,” Denton said.

Research shows that strip-till systems give tobacco yields equal to conventionally-tilled systems across a variety of conditions. No-till also performs well on loamy, well drained soils but may not do as well as strip-till on less favorable soils.

“When combined with cover crops, use of conservation-tillage may allow much shorter rotations, perhaps allowing even the more erodible fields to be in tobacco up to half of the crop rotation.” Denton said.

With tobacco’s long history of intense tillage, fields are prone to compaction, which can hurt yields because tobacco roots have a difficult time growing in or through compacted soil layers, Pearce said.

“As the size of tobacco farms has gotten larger, we have seen an increase in the potential for soil compaction to reduce growth.  With larger acreages to cover, growers have a tendency to begin tillage and transplanting operations when the soil is still wet below the surface. 

“This can lead to situation where the surface may be reasonably well prepared, but there is a zone of compaction hidden in the root zone,” Pearce said.

A shallow-rooted plant suffers quickly during dry weather, and at times will not have access to all the available nutrients in the soil.  Severe compaction can cost 200 to 400 pounds of yield lose per acre. 

It’s hard to do, but growers need to avoid tilling soils that are marginally wet, watching soil conditions 3 to 4 inches below the surface.

A cover crop can lessen soil compaction.  The roots of a winter cereal, for example, can penetrate and loosen mildly compacted layers. The cover crop can add much-needed organic matter, too.  The sod rotation, too, strengthens soils and help fields resist compaction.

“Many burley tobacco growers have asked in recent years why they don’t seem to get the higher yields they have been accustomed to in the past.  There could be a number of answers to that question, but at least one is to consider if hidden soil compaction might be limiting the potential of the crop,” Pearce said.

brad.haire@penton.com

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