Ian Kaplan

Introduction Tomatoes are among the most popular horticultural crops cultivated in high tunnels. Due to space limitations in these enclosed environments, some tomatoes are produced in succession (i.e., without rotation) across years, which could lead to yield reductions over time. However, the impact of tomato monocultures on productivity in high tunnels and strategies to buffer against yield declines need further testing. Materials and Methods We used a 4‐year field experiment whereby heirloom tomatoes (cv. Cherokee Purple and Black Krim) were grown in the same high tunnel soil over time. We tested the impact of both tomato grafting and companion planting on aboveground vegetative biomass and fruit yield. For the grafting treatment, we used the commercially available Maxifort and wild tomato, Solanum pimpinellifolium , as rootstocks. For companion planting, we seeded open alleys with clover and spatially shifted crop beds each year such that tomatoes were transplanted into the previous year's clover planting. Results Our data indicate that the companion (clover) treatment had little to no impact on tomato production, while grafting to Maxifort rootstock had a significant positive effect on biomass and yield. However, beneficial effects of grafting were only observed over time, in years three (+71% inc. in biomass) and four (+77% inc. in biomass, +38% inc. in yield) of the experiment; not during the initial 2 years. Leaf (SPAD) and fruit (Brix) metrics were unaffected by any of the treatments. Conclusion Overall, our results suggest that grafting tomatoes with commercially available rootstock is an effective tool for maintaining production in high tunnel monocultures over time.