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Technical Paper

Inverse Temperature Studies to Reduce Canopy Growth of Sweetpotato

Sweetpotato [Ipomoea batatas (L.) Lam.] cv TU-82-155 was grown in controlled environments to determine if inverse day/night temperatures could effectively control the height of the canopy without adversely affecting storage root yield. Plants were exposed to temperatures of 18/24, 24/18, 20/26, 26/20, 22/28, and 28/22°C (Experiment 1); 22/28 and the control 28/22°C (Experiment 2); and in Experiment 3, 28/22°C for the first 6-8 weeks of growth and then 22/28°C thereafter, and 22/28°C continuously. Storage root yield was either reduced by about 50% among plants grown under cool days and warm nights (Experiment 1), was similar to the control plants if plant population was increased (64 vs. 48 m-2, Experiment 2), or if cool days/warm night regimes were initiated 6-8 weeks after planting (Experiment 3). There was a substantial reduction in canopy growth (height) for inverted temperature treatments. For every 2 °C decrease there was a 3.1 cm decrease in canopy height.
Technical Paper

Using Mass Balance Techniques to Manage Nutrition of Hydroponically-Grown Sweetpotato [Ipomoea batatas (L.) Lam]

A mass balance nutrient management approach was used in controlled environment studies, to determine an appropriate nutrient solution replenishment regime for the growth of sweetpotato in nutrient film technique (NFT). Four stem cuttings (15-cm long) were planted into each of three gray PVC-1 (0.15×0.15×1.2 m) troughs in a walk-in growth chamber under a 14/10 h photoperiod, 28/22°C and 70% relative humidity. Photosynthetic photon flux at canopy level averaged 450-μmol m−2 s−1. Plants were grown with a modified half-Hoagland starter solution with an extra 3 mM of N for the first 4–6 weeks to accelerate vegetative growth, after which three refill solutions containing 1.5 (A), 4.5 (B), 0.75 (C), or 3 (A), 4.5 (B), and 6 (C) mM NO3−1-N and K, respectively, were used once per week until harvest. The level of N and K in the refill solutions did not significantly influence the number of storage roots produced.
Technical Paper

Sweet Potato Growth Parameters, Yield Components and Nutritive value for CELSS Applications

Sweet potatoes have been grown hydropon-Ically using the nutrient film technique (NFT) to provide a potential food source for long-term manned space missions. Experiments in both sand and NFT with ‘Georgia Jet’ and ‘TI-155’ cultivars have produced up to 1790 g/plant of fresh storage root with an edible biomass index ranging from 60-89% and edible biomass linear growth rates of 39-66 g m−2 d−1 in 105 to 130 days. Experiments with different cultivars, nutrient solution compositions and application rates, air and root temperatures, photoperiods and light intensities indicate good potential for sweet potatoes in Controlled Ecological Life Support Systems (CELSS).