2019 ASHS Annual Conference

Tomatoes are the gateway vegetable for home gardeners nationwide. Accordingly, tomato-related problems are among the most common questions received from the public based on a survey of County Extension agents with the New Mexico State University (NMSU) Cooperative Extension Service. Tomato planting recommendations tend to be anecdotal and widely varied for root-bound, store-bought plants intended for urban gardens. The effects of root pruning on tomato vigor and yield have not been previously reported in New Mexico. This 2018 study used a completely randomized design to explore the effects of four transplanting methods on two tomato hybrid cultivars, ‘Bella Rosa’ (determinate) and ‘Big Beef’ (indeterminate). Tomatoes were planted from seed and grown in 1-gal containers until substantially root-bound before transplanting into prepared planting beds at the NMSU Agricultural Science Center at Los Lunas. To emulate backyard growing conditions, tomato plants were spaced at 0.61 m between plants within a row and 1.52 m between rows, then caged for support. Each combination of treatment and variety was assigned randomly to four experimental units containing four plants within the same row. Data was collected from only the two inner plants. Rows were flood-irrigated approximately once per week from June through Sept. At the time of planting, root-bound plants were subjected to one of four treatments of varying root pruning intensity: (1) POP N DROP, control treatment where plants were un-potted and set directly with minimal root disturbance; (2) LIGHTLY SCUFFED, where outer surface of root ball was firmly chafed; (3) HALVED, where half of the root ball was severed completely on the diagonal; and (4) WASHED, where the entire root ball was submerged in water and washed free of soil. Dependent variables included above-ground and below ground tissue dry weights, stem caliper, and tomato yield. Yield was recorded as red tomato weights harvested when ripe and green weights of tomatoes harvested at the end of the season, just before the first frost. No differences in total tomato yield were detected between cultivars or treatments, despite extreme differences in root pruning technique at the time of planting. Significant cultivar differences were detected in dry weights and stem caliper, with ‘Big Beef’ consistently higher than ‘Bella Rosa.’ Significant treatment differences were also detected for dry weights, with the less disturbing POP N DROP and LIGHTLY SCUFFED treatments tending to have larger sizes compared to the two more extreme root pruning treatments, HALVED and WASHED.