LONG-TERM EVALUATION OF COVER CROP AND STRIP-TILLAGE ON TOMATO YIELD,FOLIAR DISEASES AND NEMATODE POPULATIONS

A 6-yr (1987-1992) experiment, continuous on the same site, evaluated potential problems for yield, nematodes and diseases with tomatoes (Ly copersicon esculentum Mill.) grown in a strip-till system. Treatments consisted of conventional tillage (CT) and strip tillage (ST), rye (Se cale cereale L.), wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) cover crops and a 2-yr rye-tomato rotation. Result s of the first 5 yr indicated a decrease in tomato yield over time for both tillage treatments and cover crops. However, yield rebounded ove rall for treatments in 1992 with the highest yield in the rye-tomato r otation. We suspect this was a result of high populations of root-knot nematodes which collapsed over the winter of 1991/1992. Tomato yields were lower following wheat and perennial ryegrass than rye. In only 1 yr out of 6, strip-tillage reduced yield compared with conventional t illage. Bacterial speck/spot symptoms on foliage, although minor, were significantly greater in ST than in CT plots during the last 3 yr. No major trends in incidence and severity of bacterial and fungal diseas es and of disorders of fruit were evident during the 5-yr period and n either fruit yield nor quality were significantly affected by these fa ctors. Root-knot nematodes (Meloidogyne hapla Chitwood) were numerical ly less in the rye-tomato rotation than in other treatments; both root -knot and root lesion nematodes (Pratylenchus penetrans [Cobb]) tended to be less numerous under CT than under ST. Strip-tillage is feasible for machine harvest processing tomatoes. However, we are concerned ab out the tendency of tomatoes grown under reduced tillage to have lower yields than those grown under conventional tillage. More work is requ ired on the interactions of cultivars, cover crops and nematodes in so il conservation systems.