Effects of Grafting and Landscape Fabric on Productivity of Three Organically Grown Heirloom Tomato Varieties in High Tunnels

Consumers continue to become more health conscious and seek out organically and sustainably grown produce such as tomatoes (Solanum lycopersicum) to support healthy diets. With the high demand for early fresh produce and the premium price it commands, achieving maximum yield from each tomato plant is very desirable. Organic tomatoes, especially heirlooms, have been favored at direct markets such as farmers’ markets and Community Supported Agriculture. With high tunnels becoming widely used, season extension of tomato production is practical but not without challenges, among which are soil-borne diseases, weeds, and low soil temperatures in early spring. The objective of this research was to examine if grafting and landscape fabric would increase the yield potential of tomatoes grown organically in high tunnels for early season harvest. In this two-year study, heirloom tomatoes (German Johnson, Cherokee Purple, and Red Brandywine in 2010; Paul Roberson replaced Red Brandywine in 2011) were grafted on Maxifort rootstock using the silicon tube method in the greenhouse. Grafted and non-grafted transplants were either planted on bare ground or on black landscape fabric (BLF) covered ground with holes cut for transplants in high tunnels. Trials were conducted at North Carolina A&T State University Farm in Greensboro, North Carolina. The BLF was used primarily for weed control and to promote possible higher soil temperatures in early spring. In 2010, no significant difference was observed between grafted and non-grafted cultivars or between the bare soil and BLF treatments in terms of total marketable yield, which was highest with German Johnson, followed by Cherokee Purple and Red Brandywine. In 2011, total yield and number of fruit were also not different between the grafted and non-grafted cultivars, or between the bare soil and BLF treatments. For early yield, there was an interaction between cultivars and BLF treatment.  No difference existed between grafted and non-grafted tomato varieties grown in bare soil. In BLF treatment, grafted Cherokee Purple and German Johnson had significantly lower yields than the non-grafted ones, while grafted Paul Roberson had significantly higher early yield than the non-grafted. Our two-year data suggest that grafting may not be an economical approach in organic heirloom tomato production if disease pressure is not evident in high tunnel soils.