A glasshouse study was conducted to evaluate the suitability of composted broiler chicken (Gallus gallus) litter as a potting substrate using lettuce (Lactuca sativa L.). Broiler litters containing wood shavings or peanut bulls as bedding materials were composted with either shredded pine bark or peanut hulls. Composted materials were then combined with a commercially available potting substrate. Greatest fresh weight yield was obtained when peanut bull compost was mixed with commercial potting substrate at a ratio of 3:1. Fresh weight was less with pine bark compost than with peanut hull compost. However, there were no differences in lettuce dry weight among composts except for pine bark composted with wood-shaving broiler litter. The pH of this material was below the lettuce tolerance level for mixes at or above 50% compost. There was no evidence of lettuce physiological disorders resulting from excessive nutrient concentration. Most elements analyzed (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, and Al) were within or slightly above sufficiency ranges for Boston-type leaf lettuce. It appears that composting broiler litter for use as a potting substrate or component would be one suitable alternative to land application in the southern United States. We recommend, however, that the pH of substrates be adjusted to suit desired crop requirements.
The first goal of this study was to determine the packaging film O2 permeability required to maintain a steady-state O2 concentration of 3% in modified-atmosphere packaging (MAP) of minimally processed romaine lettuce (Lactuca sativa L.). The second goal of the study was to determine the extent to which MAP could preserve lettuce quality and consequently extend product shelf life. Oxygen consumption rates of commercially prepared lettuce samples were determined in a closed system for each of three atmospheres (3% O2 combined with either 6%, 10%, or 14% CO2). Enzymatic, quadratic, and linear mathematical models were compared to determine which best described the respiratory data. The linear model was the most suitable and was used to predict the O2 consumption rate of the minimally processed romaine lettuce under the desired package headspace gas concentrations. The predicted O2 consumption rate was used to calculate the necessary O2 permeability for the packaging film. Packages (21.6 × 25.4 cm) were constructed from a polypropylene-polyethylene-laminate film with the appropriate O2 permeability. Packaged samples were stored under three modified atmospheres (MAs) (3% O2 combined with either 6%, 10%, or 14% CO2) for 20 days, and headspace gas concentrations, lettuce appearance, and color were evaluated every other day. Growth of pectinolytic and lactic acid bacteria was also studied. The O2 consumption rate of the lettuce decreased with increasing CO2 levels. The O2 levels in the MA packages equilibrated at 7% to 11%. Compared to a control atmosphere of air, MAP delayed the development of tissue discoloration. Preliminary results indicated no effect of MAP on microbial growth. Of the three CO2 levels, 10% was slightly more effective than 6% and 14%. Critical choice of packaging permeabilities combined with MAP maintained the quality of minimally processed romaine lettuce and thereby increased shelf life by about 50%.
Experiments were conducted to study the effect of temperature on the ethylene inducibility of phenylalanine ammonia lyase (PAL, EC 4.3.1.5) activity and the development of russet spotting (RS) in Iceberg lettuce (Lactucu sutiva L.). Tissue exposed to ethylene and held at 15 or 20C showed earlier hut lower peaks in PAL activity than tissue held at 5C. Accumulation of total soluble phenolic compounds, and the development of RS paralleled increases in PAL activity after a short lag period. Lettuce tissue transferred from 5 to 15C after 1 to 3 days showed later hut higher peaks in PAL activity than tissue continuously held at 15C. Transferring ethylene-exposed tissue to 0C before RS symptoms developed greatly limited further rise in PAL activity and RS development. Discontinuing ethylene exposure after 4 days resulted in a rapid decrease in PAL activity. Lettuce tissue exposed to ethylene for 4 days and then transferred from 5 to 0C after the development of moderate RS symptoms showed no difference in RS after 8 days compared to tissue stored continuously at 5C.
approach to using the N in the atmosphere, transforming it into a form readily used by plants. We describe a field study in which PFN is used as a biostimulant for romaine lettuce ( Lactuca sativa var. longifolia ) grown in the Salinas Valley, CA, USA
treatment). The other half of the chamber remained at full intensity, which was 420 ± 20 μmol·m −2 ·s −1 (high light treatment). Plant material preparation. Seeds of radish ( Raphanus sativus ‘Cherry Bomb II’), lettuce ( Lactuca sativa ‘Outredgeous’ and
Lettuce ( Lactuca sativa ) is an important cool-season vegetable crop species, with more than 2 million tonnes produced in the United States in 2019 [U.S. Department of Agriculture (USDA), National Agricultural Statistics Service, 2020]. The ideal
Lettuce aphid ( Nasonovia ribisnigri Mosley) has affected lettuce ( Lactuca sativa L.) production in Europe since the 1970s and became a serious problem on lettuce in British Columbia, Canada, in 1981 ( Forbes and MacKenzie, 1982 ). It was
). Tipburn is a physiological disorder usually observed in the leaves of vegetable plants such as lettuce ( Lactuca sativa ) ( Saure 1998 ). Tipburn symptoms are irreversible and can cause entire yield losses for growers. These losses are caused by a
produce similar biomass and phytochemical levels compared with HPS lamps at reduced energy cost for lettuce grown in a hydroponics setup. Materials and Methods Lettuce plant culture The Boston head lettuce ( Lactuca sativa var. capitata ) was provided by
196 198 Gray, D. 1975 Effects of temperature on the germination and emergence of lettuce ( Lactuca sativa L.) varieties J. Hort. Sci. 50 349 361 10.1080/00221589.1975.11514644 Guedes, A.C. Cantliffe, D.J. 1980 Germination of lettuce seeds at high