Effects of Recently Incorporated Organic Amendments on Damping-Off of Conifer Seedlings

Abstract

grow seedlings in the greenhouse for Wall, R. E. 1984. Effects of recently incorporated organic amendments on damping-off of conifer pathogenicity studies with damping-off seedlings. Plant Disease 68:59-60. and root rot fungi. Populations of Fusarium oxysporum Schlect., Rhizoctonia In greenhouse tests, forest nursery soil containing the damping-off fungi Fusarium oxysporum, solani Kihn, Pythium spp. and Rhizoctonia solani, and Pythium spp. was planted to oats (Avena sativa), rye (Secale cereale), ' ' buckwheat (Fagopyrum esculentum), and red clover (Trifolium pratense). After 15 and 20 wk, Cylindrocarpon spp. were therefore these green manure crops were incorporated into the soil, which was then amended with two levels present. each of sphagnum peat or fresh conifer sawdust. Black spruce and jack pine planted on these soils Soils were mixed thoroughly, screened were not significantly affected by the peat or sawdust amendments but the oat, rye, and red clover through a sieve with 0.5-cm openings, green manure crops caused an increase in postemergence damping-off. Jack pine was most affected and placed in wooden flats 30 X 50 X 6 by 15-wk-old oats and rye. Black spruce had the most postemergence damping-off in soil cm, which were placed in the greenhouse containing 15-wk-old red clover. Based on these results and earlier studies, it is suggested that any and watered daily. After 1 wk, half of the green manure crop is potentially damaging if incorporated into soil immediately before planting. flats were planted to green manure crops, and 5 wk later, the remainder were planted (with the exception of the Undecomposed plant residues incor- plant residues have been found to controls, which were left unplanted). The porated into soils before planting can increase for 10-25 days after incorporation green manure crops, oats (Avena sativa have various effects on the ensuing crop. and then decrease (13). Decomposed L. 'Stormont'), rye (Secale cereale L. Beneficial effects include improved soil sawdust is considered superior to fresh 'Kustro'), buckwheat (Fagopyrum escutilth, aeration, moisture-holding capacity, sawdust as an organic amendment in lentum 'Redstraw'), and red clover improved root penetration, and sup- forest nurseries (8,18). (Trifolium pratense L.), were grown pression of pathogenic microorganisms Certain fresh plant residues appear during the summer in a glass greenhouse