Effects of Rootstock and Location on Open Field ‘BHN 589’ and ‘Nebraska Wedding’ Grafted Tomato Yield

Grafted tomato ( Solanum lycopersicum ) production is popular, particularly in high tunnels, because grafted plants can mitigate soilborne disease incidence in highly infested soils and increase water and nutrient use efficiency and crop yield and quality. However, these potential benefits are not as well documented in open field production systems with less disease pressure. The objective of this study was to quantify the effect of tomato grafting on fruit yield, number, and size across 2 years (2018 and 2019) and three diverse open-field production environments in Nebraska (Lincoln, North Platte, and Dwight). At each location, a scion from one of two determinant fresh market tomatoes, ‘Nebraska Wedding’ (heirloom) or ‘BHN 589’ (commercial hybrid), were grafted onto one of two rootstocks, ‘Estamino’ and ‘Maxifort,’ and the nongrafted scion cultivars were controls. In year 2, a fertilizer treatment was introduced (0 and 50 kg·ha −1 N). Ripe tomatoes were harvested weekly, sorted as marketable or cull, counted, and weighed fresh. No marketable or total yield benefits of grafting were observed in 2018 for any scion by rootstock combination across locations. Marketable yield of grafted plants was reduced by 32% in Lincoln. However, grafted ‘Nebraska Wedding’ plants (regardless of rootstock) in North Platte (with coarse-textured, lower organic matter soil) increased fruit number (but not yield) by 50% to 63%. In 2019, grafting ‘BHN 589’ to ‘Maxifort’ increased total tomato yield by 24% across all locations. The heirloom variety Nebraska Wedding did not benefit from grafting in 2019. ‘Estamino’ rootstock did not increase tomato yield, number, or size for either scion variety in either year. Nitrogen fertilizer increased yield as expected in 2019, but grafted plants did not perform better than nongrafted under reduced nitrogen fertility. Results from this study suggest that grafting is not consistently beneficial to ‘BHN 589’ and ‘Nebraska Wedding’ in open field production systems in Nebraska, particularly if there are no known soilborne disease issues.