Soil Amendment with Cabbage Residue and Crop Rotationto Reduce Gummy Stem Blight and Increase Growth and Yield of Watermelon. Anthony P. Keinath, Assistant Professor, Clemson University, Department of Plant Pathology and Physiology, Coastal Research and Education Center, 2865 Savannah Highway, Charleston, SC 29414-5332. Plant Dis. 80:564. Accepted for publication 1 February 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0564.

Three cropping sequences, watermelon-cabbage-soil solarization-watermelon, watermelon-wheat-soybean-watermelon, and 3 years watermelon, were evaluated for the effect on gummy stem blight and watermelon fruit yield. The 3-year experiment was conducted three times, first in the fall of 1991 through the summer of 1993, then twice in the fall of 1993 through the summer of 1995, with one of these being a second cycle in the same plots as the first test. Cab-bage-solarization (P ≤ 0.07) and the wheat-soybean double crop (P < 0.04) reduced area under the disease progress curve for gummy stem blight in two experiments when compared with yearly cropping of watermelon. Plant stand, vine length, and fruit set were increased by 31, 26, and 64%, respectively, in cabbage-amended, solarized plots compared with the other two cropping sequences. Averaged across first-cycle experiments in 1993 and 1995, cabbage followed by soil solarization significantly (P ≤ 0.01) increased the weight and number of marketable-sized (>6.35 kg) and total healthy fruit compared with the nonsolarized treatments. Marketable yields of cv. Charleston Gray were 59.4, 35.4, and 39.4 kg of watermelon per 15 m of row in plots cropped to cabbage-solarization, watermelon, and wheat-soybean, respectively, the preceding year. Yield of watermelons weighing <6.35 kg was greater (P ≤ 0.04) after cabbage amendment and solarization than after the other two cropping sequences for both experiments in 1995. In 1994, thermotolerant fungi increased in solarized plots amended with cabbage residue and remained significantly (P < 0.01) higher in these plots than in nonsolarized plots the following year. Growth promotion and fruit yields in amended, solarized plots were not associated with changes in soil mineral nutrients, plant parasitic nematodes, or soil temperatures. Incorporating cabbage residue into mulched soil can increase growth and yield of watermelon.