5.1.15
SOILBORNE PATHOGENS IN A SWEET CORN-SNAP BEAN DOUBLE CROP WITH POULTRY LITTER SOIL AMENDMENTS

DR SUMNER, MR HALL, JD GAY, G MACDONALD, SI SAVAGE and K BRAMWELL

Coastal Plain Experiment Station and Rural Development Center, University of Georgia, Tifton, GA 31793-0748, USA

Background and objectives
A steady rise in chicken production for meat and eggs has increased the amount of poultry litter available for distribution on fields in Georgia. This research was initiated to determine the influence of different poultry litter amendments and tillage practices on populations of soilborne pathogenic fungi and root diseases in intensive vegetable culture [1, 2].

Materials and methods
A spiit-plot experiment was established in a field of Tifton loamy sand (fine loamy, siliceous, thermic, Plinthic Kandiudults). Whole plots were five replications of two tillage practices: conservation (subsoiled each fall) and conventional (turning soil with a mouldboard plough before each vegetable crop). Subplots were four soil amendments: non-composted broiler litter, non-composted breeder litter, composted breeder litter, and no litter. Each subplot received commercial fertilizer as needed to ensure optimum crop production based on nutrient analysis of litter, soil and plant tissue. The Jitters were broadcast at 11,200 kg/ha 3-4 weeks before planting sweet corn in March and again before planting snap bean in August. Winter rye was grown no-till in all subplots from November to February. The experiment was continued for 2 years.

Results and conclusions
In sweet corn, there were no differences in populations of Rhizoctonia solani in soil or in crown and brace root rot among treatments, but populations of Pythium spp. and total fungi in soil were increased by all litter treatments in the second year. In the second year, populations of Fusarium spp. and total fungi were increased by conservation tillage compared with conventional tillage. In snap bean, there were no differences in populations of R. solani anastomosis group (AG) 4 or Pythium spp. among litter treatments, but litter treatments had a variable effect on binucleate Rhizoctonia spp. In the second year, post-emergence damping-off was increased by non-composted broiler litter compared with no litter. Tillage practices did not affect root and hypocotyl disease severity or post-emergence damping-off.

References
1. Huber DM, Sumner DR, 1996. Rhizoctonia species: Taxonomy, Molecular Biology, Ecology, Pathology, and Disease Control, pp. 433-443.
2. Riegel C, Fernandez FA, Noe JP, 1996. Journal of Nematology 28, 369-378.