The objectives were to 1) compare growth and yield of different ginger (Zingiber officinale) and turmeric (Curcuma longa) propagules grown under two photoperiods (Expt. 1); and 2) evaluate whether their growing season could be extended with night interruption lighting (NI) during the winter (Expt. 2). In Expt. 1, propagules included 1) micropropagated tissue culture (TC) transplants, 2) second-generation rhizomes harvested from TC transplants (2GR), and 3) seed rhizomes (R). Plants received natural short days (SDs) or NI providing a total photon flux density (TPFD) of 1.3 µmol·m−2·s−1. Providing NI increased number of new tillers or leaves per plant, rhizome yield (i.e., rhizome fresh weight), and dry mass partitioning to rhizomes in both species. There was no clear trend on SPAD index in response to photoperiod or propagative material. Although TC-derived plants produced more tillers or leaves per plant, 2GR ginger and R turmeric produced a higher rhizome yield. In Expt. 2, seed rhizomes of ginger and turmeric were grown under five treatments with different photoperiods and/or production periods: 1) 20 weeks with NI (20NI), 2) 24 weeks with NI (24NI), 3) 28 weeks with NI (28NI), 4) 14 weeks with NI + 10 weeks under natural SDs (24NISD), and 5) 14 weeks with NI + 14 weeks under natural SDs (28NISD). NI provided a TPFD of 4.5 µmol·m−2·s−1. Lengthening the production period and providing NI increased rhizome yield and crude fiber content in both species. SPAD index decreased when plants were exposed to natural SDs at the end of the production period (NISD treatments). Results demonstrate the potential to overcome winter dormancy of ginger and turmeric plants with NI, enabling higher rhizome yield under natural SDs.

Excess solar radiation can negatively affect growth and rhizome yield of ginger (Zingiber officinale) and turmeric (Curcuma longa) plants. Thus, the objective of this study was to evaluate the effect of 60% shade nets (Experiment 1) as well as white and red kaolin sprays during two production stages (early establishment vs. entire cycle) (Experiment 2) on field-grown ginger and turmeric plants. In Experiment 1, plants were propagated from seed rhizomes (R) or second-generation rhizomes from tissue-cultured plants (2GR), while only R were used in Experiment 2. There were no differences in rhizome yield in response to shade in Experiment 1, with mean values of 644 and 692 g in ginger and turmeric, respectively. Overall, 2GR ginger plants produced a higher rhizome yield (880 g) than R plants (425 g), but no yield differences were measured in turmeric. In Experiment 2, for both species and regardless of kaolin color, sprays applied during the entire cycle increased photosynthesis and stomatal conductance and reduced leaf temperature and transpiration compared to control. Rhizome yield was also up to 87% higher in ginger and 47% higher in turmeric plants sprayed with kaolin. Spraying plants with white kaolin during the early season establishment of these crops can be an effective strategy to reduce radiation stress for open-field production.

Ginger and turmeric are tropical plant species with medicinal, beverage, and edible uses. Both species are typically propagated using seed rhizomes that often lack uniformity when sprouting, ultimately affecting the transplant growth and quality. Our objectives were to (1) develop a model to predict the effect of temperature on rhizome sprouting and transplant growth and (2) characterize the morphological factors affecting the sprouting of ginger and turmeric rhizomes. Two experiments were conducted where the rhizomes were placed in plastic bags with a moist substrate inside dark incubator chambers. Five temperature treatments (21, 25, 27, 30, and 32 °C) were used for calibrating the model, and six temperature treatments (14, 20, 25, 30, 35, and 40 °C) were used in the validation phase. The number of days for rhizomes to develop 1- and 5-cm sprouts were counted; after which, the total number of sprouts, total leaf length, and root quality were measured. A nonlinear regression analysis was used to develop temperature–response curves. Ginger and turmeric had optimal sprouting temperatures of 27.5 and 30.1 °C, respectively. Temperatures close to the optimal reduced the time to sprout and to subsequently reach the transplant stage. No sprouting was observed at 14 °C, and the minimum temperature to develop 5-cm sprouts was estimated at slightly above 17 °C in both species. Temperatures above 32 °C resulted in tissue damage and rhizome loss. The results from this study show the potential to produce uniform ginger and turmeric transplants using temperature treatments that accelerate sprouting.

Intumescence is a physiological disorder that affects some tomato (Solanum lycopersicum) cultivars grown in environments lacking ultraviolet radiation. Both far-red (FR) radiation and blue light have been shown to help mitigate this disorder. Thus, the objectives of this study were to characterize and compare intumescence injury and growth of various tomato cultivars propagated under different radiation qualities (Expt. 1) and to evaluate plant responses to the interactive effect of radiation quality and relative humidity (RH) (Expt. 2). Seedlings of six cultivars in Expt. 1 were grown under broad band white light (W), W and blue with (WBFR) or without (WB) FR radiation, and blue and red light with FR radiation (BRFR). Seedlings of four cultivars in Expt. 2 were grown under W or WBFR and a low (≈50%) or high (≈95%) RH. In both experiments, seedlings were grown under a daily light integral of ≈13 mol·m‒2·d‒1 (200 ± 4 μmol·m‒2·s‒1 for 18 h·d−1). FR radiation was provided using 20 ± 2 μmol·m−2·s−1 delivered throughout the entire photoperiod or at the end-of-day (EOD) in Expts. 1 or 2, respectively. Intumescence was generally suppressed when seedlings in Expt. 1 were grown under BRFR and WBFR, which also corresponded with the general response to stomatal conductance (gs). In contrast, seedlings grown under W had the highest incidence of intumescence, ranging from 23% to 69% across cultivars. The high blue photon flux (PF) ratio in WB was not effective at suppressing intumescence injury without FR radiation, although incidence and severity were lower compared with W. In Expt. 2, intumescence incidence was generally lower in seedlings grown under WBFR, and RH had small effects on intumescence. In both experiments, younger leaves were relatively less affected by intumescence, suggesting that a developmental factor is associated with the disorder. As expected, providing FR radiation resulted in a general increase in stem height across cultivars and in both experiments. The high RH provided in Expt. 2 also resulted in an increase in stem height. However, seedlings under low RH produced larger leaves, lower specific leaf area, and more shoot dry mass than those under high RH. Overall, our findings show that applying FR radiation helps suppress intumescence, but strategies are needed to minimize issues with excessive stem elongation.

Domestic production of ginger (Zingiber officinale) and turmeric (Curcuma longa) rhizomes is increasing. The objective of this study was to compare growth and rhizome yield of these crops using different container volumes and planting densities. Two greenhouse experiments that lasted 28 weeks each were conducted. In Expt. I, one sprouted rhizome of a single ginger variety (Bubba Blue) and four turmeric varieties (Hawaiian Red, BKK, White Mango, and Black) were transplanted into either small (1.5 gal) or large (13.3 gal) round containers. In Expt. II, either one or three sprouted rhizomes of two ginger varieties (Bubba Blue and Madonna) and two turmeric varieties (Indira Yellow and Hawaiian Red) were transplanted into either large (13.3 gal) or medium (3.9 gal) round containers. In Expt. I, there were an increase in plant growth and yield with increasing container volume, as both crops produced more than double the shoot, root, and rhizome fresh weight (FW) when grown in large compared with small containers. In Expt. II, rhizome yield of ginger was 44% higher in medium than large containers, and container volume did not affect yield in turmeric. Total dry weight (DW) was higher in plants grown in the larger container volume in both species in Expt. I, and turmeric only in Expt. II. However, ginger in Expt. II had an 18% higher plant DW in the medium compared with the large container. The higher density in Expt. II increased yield and biomass production per container compared with the lower density, regardless of variety and container volume. Overall, net revenue per container was higher in Expt. II than Expt. I because of the higher rhizome yield. In Expt. I, the higher yield of ginger compared with turmeric increased sales revenue of this species, despite a lower sales price per kilogram. In contrast, the higher yield of turmeric in Expt. II resulted in higher sales revenue and net revenue per container compared with ginger. Based on our results, medium containers could be used to minimize material and space costs for ginger and turmeric production under the conditions evaluated in our study.