EFFECT OF CHICKEN COMPOST OR AMMONIUM PHOSPHATE AND SOLARIZATION ON PATHOGEN CONTROL, RHIZOSPHERE MICROORGANISMS, AND LETTUCE GROWTH

Two field experiments were conducted to determine effects of commercial chicken compost, ammonium phosphate fertilizer, and solarization, alone or combined, on several soilborne pathogens and the growth and yield of lettuce (Lactuca sativa). Southern root-knot nematode (Meloidogyne incognita) present at one of the sites was effectively controlled by the combination of these treatments, whereas solarization alone gave only partial control. Pythium ultimum was controlled by both solarization alone and combined with chicken compost. Lettuce yield was significantly increased by most solarization treatments in successive fall and spring crops at both locations. However, an inhibitory effect on lettuce growth and yield in the fall crop was observed in the plots that were amended with compost after solarization. The rhizosphere of lettuce plants grown on solarized soils was intensively colonized by fluorescent pseudomonads and Bacillus spp. Numbers of P. ultimum and other fungi were suppressed in solarized plots during the two successive lettuce crops.