EFFECT OF SOLARIZATION ON SOILBORNE PATHOGENS AND WEEDS IN SHORT-DAY, SWEET ONIONS IN GEORGIA.

K.W. Seebold, F.S. Sanders, J.C. Diaz-Perez, and R.D. Gitaitis.

Coastal Plain Experiment Station, University of Georgia, Tifton, GA 31793-0748. kseebold@tifton.uga.edu.

Soils with ten years of onion production were harrowed, shaped into beds and covered with clear plastic (3.0 mil thickness) for a minimum of 10 wks in mid-summer in southern Georgia in 2002 - 2004. In 2003, total yield, mean bulb weight, and number of jumbo grade onions were significantly higher and pink root (Phoma terrestris) levels were significantly lower in solarized plots. In 2004, trends were similar for total yield, mean bulb weight, number of jumbo grade bulbs, but were not significantly different. However, number of small grade bulbs and pink root levels were significantly lower in solarized plots in 2004. Significantly fewer bulbs with Fusarium basal rot occurred in solarized plots in 2003, but because of lack of disease pressure in 2004 there were no significant differences among treatments. However, solarization had a long-term impact on reducing total number of fungi / g soil in both years. In addition, solarization significantly reduced the numbers of weeds, particularly yellow nutsedge, in onion plots in 2004. Although having no impact on bacterial diseases in the 2002-2003 season, a second year of solarization reduced the number of colony-forming-units (CFU) of Burkholderia cepacia / g soil a thousand fold in the 2003-2004 onion season. Although not significant, solarized plots yielded a lower percentage of onions with sour skin in 2004.

to the 2004 National Allium Research Conference Home Page