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.

The objective was to analyze the physical, chemical, and biological water quality in horticulture irrigation systems in 24 ornamental plant greenhouses and nurseries in the United States. At each greenhouse or nursery, water was collected from up to five points (“Sample Types”) which included 1) “Source” from municipal or private well supplies, 2) “Tank” from enclosed storage containers, 3) “Subirrigation” from water applied to crops in ebb-and-flood systems, 4) “Furthest Outlet” that were irrigation emitters most distant from the Source, and 5) “Catchment Basin” from open outdoor retention areas. On average, Source water had the highest physical and microbial quality of Sample Types including the highest ultraviolet (UV) light transmission at 86%, lowest total suspended solids (TSS) at 3.1 mg·L ⁻¹ , and lowest density of aerobic bacteria with 1108 cfu/mL of water. Average quality of recycled water from Subirrigation or Catchment Basins did not meet recommended levels for horticultural irrigation water for UV transmission (68% to 72% compared with recommended 75%), microbial counts (>100,000 cfu/mL compared with recommended <10,000 cfu/mL), and chemical oxygen demand (COD) (48.2 to 61.3 mg·L ⁻¹ compared with recommended <30 mg·L ⁻¹ ). Irrigation water stored in Tanks or applied at Furthest Outlets had lower physical and biological water quality compared with Source water. Level of aerobic bacteria counts highlighted a risk of clogged microirrigation emitters from microbial contaminants, with highest bacteria levels in recirculated irrigation water. The physical, chemical, and microbial water quality results indicate a need for more effective water treatment to improve biological water quality, particularly with recirculated irrigation.

Unreacted residual limestone in the container substrate is key in buffering pH change over time. Our goal was to develop a substrate test protocol to measure residual lime [in units of CaCO ₃ equivalent (CCE)] by applying a strong mineral acid (HCl) to a substrate sample and measuring the evolved CO ₂ gas with a gasometric method based on a Chittick apparatus. In one experiment, CaCO ₃ was added to a substrate that had previously been neutralized to pH 7.35 with Ca(OH) ₂ so that there would be minimal CaCO ₃ reaction with the substrate at this high pH. The gasometric method was then used to estimate residual CCE. Measured CCE and applied CaCO ₃ were similar, indicating reliable CCE estimation. In a second experiment, a pH titration method was used to quantify the relationship between substrate-pH and milliequivalents of reacted base and provided an additional validation of the estimated reacted and residual CCE. The gasometric method demonstrated declining residual CCE over time as a dolomitic limestone reacted to raise substrate-pH and increasing residual CCE as applied CaCO ₃ concentration increased. Residual CCE in a substrate is an important property that should be considered for pH control and management in greenhouse crop production. Our results indicate that the gasometric system may be useful for optimizing lime application rate, lime source, or management of residual CCE during crop production.