2017 ASHS Annual Conference

Bare-root strawberry (Fragaria × ananassa Duch.) transplants initially have limited water and nutrient uptake capacity because their roots are mostly desiccated prior to transplanting. Therefore, the promotion of new root growth is the key to their successful establishment. We used a scanner-based rhizotron system to characterize root morphological responses of bare-root strawberry (‘Florida Radiance’) transplants to nitrogen (N) fertilization rates. The rhizotrons had 2655 cm³ of soil volume with a 22.9 × 30.5 cm scannable window. Soil was collected from the strawberry field and packed in the rhizotrons using the field bulk density. After transplanting into the rhizotrons, plants were watered by micro-sprinklers for 10 days to simulate the field establishment. Thereafter, N was applied daily by fertigation at 0.56, 1.12, 1.68, 2.24, 2.80 and 3.36 kg/ha/d for up to 33 days. Leaf area, leaf chlorophyll index, total root length, root surface area showed exponential increases with N reaching a plateau at 2.24 kg/ha/d, although the root responses occurred with a time lag of over a week compared to the leaf traits. At the end of the experiment, these traits maintained the similar responses, whereas crown diameter and number of new primary roots increased linearly with N up to 3.36 kg/ha/d. Correlation analysis between shoot and root traits revealed that leaf area had the highest positive correlation with total root length, and crown diameter had the highest positive correlation with new primary root number. These results suggest that the promotion of leaf and crown growth are important to stimulate new root formation and elongation for newly planted bare-root strawberry transplants. During the establishment period, the use of relatively high N fertilization (2.24 to 3.36 kg/ha/d) compared to the average in-season rate (0.56 to 1.12 kg/ha/d) may be an effective strategy to improve their early growth and development.