Potassium deficiency limits Virginia cotton yields

Final yield totals are not complete for Virginia’s 2006 cotton crop, but it’s clear that in some areas of the state potassium deficiency caused early defoliation and loss of a part of what at one time looked like a bumper crop.

Virginia Cotton Specialist Joel Faircloth says there are numerous reasons for potassium deficiency in Virginia.

The first is a result of 900-plus pound per acre cotton yields in 2004 and 2005 and a high boll load in 2006. Successive high yielding cotton crops have placed a high demand on all nutrients, including potassium.

In 2006, early spring rains restricted root growth in early planted cotton throughout the Virginia cotton-producing belt. The cotton crop was set up with a small root mass, then the drought came, and there was no extended root system to go out and get nutrients — those is short supply were the hardest to absorb for the cotton plant, Faircloth explains.

“We have seen more potassium deficiency this year, and it tends to show up more in sandy soils than in heavier soils,” Faircloth says.

At the Tidewater Area Research and Extension Center in Holland, Va., potassium deficiency showed up about mid-season, according to Faircloth.

“Once the margin of the leaves starts to crinkle from potassium deficiency, leafspot sets in, ethylene production increases, and leaves start to fall off. Then, growers don’t have to worry about defoliation, but they will see some significant yield losses, Faircloth says.

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