CARROT, ONION, CELERY AND LETTUCE CROP SUCCESSION STUDIES ON AN ORGANIC SOIL

Crop successions involving carrot (Daucus carota L.), onion (Allium cepa L.) celery (Apium graveolens L.) and lettuce (Lactuca sativa L.) were organized to study the effect of each crop on the yield of the subsequent crops when grown on an organic soil. Crop sequences affected yields significantly. Carrot yields were significantly greater when they followed celery or lettuce than when they followed carrot or onion. Onion yields were greatest after celery or lettuce, less after onion, least after carrot. Celery yields were greatest after celery or lettuce, less after onion, least after carrot. Lettuce yields were greater after lettuce or celery than after onion or carrot. The nematode species occurring in the largest numbers after continuous growing of carrot, onion, celery, and lettuce were Meloidogyne hapla, Paratylenchus hamatus, Pratylenchus penetrans and M. hapla, respectively.