2018 ASHS Annual Conference

Grafting heirloom tomato (Solanum lycopersicum) cultivars onto hybrid tomato rootstocks can increase yield, mineral nutrition, drought tolerance and disease resistance. In 2017, the determinant heirloom tomato ‘Nebraska Wedding’ was grafted onto two rootstocks, ‘Estamino’ and ‘Maxifort’. Non-grafted and self-grafted ‘Nebraska Wedding’ plants were controls. Plants were grown in a high fertility soil in Lincoln, NE (residual NO₃-N = 10.7 ppm; P = 90 ppm, and K = 410 ppm), and in a low fertility soil near Mead, NE (residual NO₃-N = 3.2 ppm; P = 5.5 ppm, and K = 296 ppm). Plants received no nitrogen fertilizer (control) or 168 kg N ha^-1 from yardwaste compost, calcium nitrate [Ca(NO₃)₂] fertigation, or both (84 kg N ha^-1 from each source). In the high fertility soil, grafting tomatoes with ‘Estamino’ or ‘Maxifort’ reduced yield by 41% and 48% relative to non-grafted plants. Fertilizer and compost did not affect tomato yield in the high fertility soil, but did increase leaf nutrition. In the low fertility soil, tomatoes grafted to ‘Estamino’ had 20% greater yield than non-grafted plants. Fertilizing with Ca(NO₃)₂ alone and in combination with compost also increased tomato yield in the low fertility soil, and plants grafted to ‘Maxifort’ and fertilized with Ca(NO₃)₂ and compost had greater leaf tissue nitrogen, phosphorus, and potassium. Results suggest that grafting and integrated nitrogen management can increase tomato yield and leaf nutrition, especially in a low fertility soil. However, grafted tomatoes grown in a high fertility soil may have excessive vigor and reduced harvest index.