INTERACTION AMONG MYCORRHIZAE, SOIL SOLARIZATION, METALAXYL, AND PLANTS IN THE FIELD

Field trials were conducted in 1988 and 1989 to increase growth response, yield, and vesicular-arbuscular mycorrhizal (VAM) fungi colonization of cotton (Gossypium hirsutum), onion (Allium cepa), and pepper (Capsicum annuum) in nonfumigated soil. Treatments of fumigated and nonfumigated soil plots included soil solarization, soil solarization plus tarp coverage for 2 wk after planting, and metalaxyl application. Plants from each treatment were inoculated or not inoculated with VAM fungi. Because results were similar in both years, only those for 1989 are given. Fresh weight and boll number of cotton were highest in VAM-inoculated plants grown in nonfumigated soil after soil solarization, soil solarization plus tarp coverage, and metalaxyl application. Fresh weight of onion was highest in VAM-inoculated, nonfumigated, solarized soil, with or without tarp coverage. Fresh weight and fruit weight of VAM-inoculated pepper plants were one to two times greater in nonfumigated soil than in fumigated soil, and both were greatest in VAM-inoculated, solarized soil and in solarized soil plus tarp coverage. Fresh weight and yield of the three crops were highly correlated with percent root colonization by VAM 5 wk after planting. VAM colonization of roots of cotton, onion, and pepper was maximum (65, 59, and 63%, respectively) at 3.5-5 wk after planting in nonfumigated plots treated by soil solarization plus tarp coverage. Roots of cotton, onion, and pepper were longest (149, 51, and 94 cm, respectively) in soil solarized and tarped, whether VAM-inoculated or not. Benefit of VAM inoculation appears greatest with solarization and solarization plus tarp coverage.