Eggplant (Solanum melongena L.) is an increasingly popular crop in the United States. In the southeastern United States, eggplant is often produced with high levels of irrigation water [above the rate of crop evapotranspiration (ETc)], resulting in water waste and nitrogen (N) leaching. The objective of this research was to assess the effects of irrigation rate on plant growth and fruit yield in eggplant. The study was conducted in Tifton, GA, in the fall of 2010 and 2011. Eggplant plants cv. Santana were grown on raised beds (1.8 m centers) covered with white plastic film mulch. There was a single drip tape along the center of the bed. The design was a randomized complete block with five treatments and four replications. Treatments consisted of irrigation rates based on ETc (33%, 67%, 100%, 133%, and 167% ETc). Plant growth, chlorophyll index (CI), and volumetric soil water content (SWC) were monitored over the season. In 2010, SWC (0–30 cm deep) increased and soil nitrate levels decreased with increasing irrigation rates. Foliar N and potassium (K), and CI decreased with increasing irrigation rate, probably due to a dilution effect. Stem diameter, leaf dry weight (DW), and vegetative top DW increased with increasing irrigation rate. Net photosynthesis and stomatal conductance (g S) were lowest at 33% ETc. Fruit number and fruit yields (marketable and total) were also lowest at 33% ETc and there were little yield differences among irrigation rates higher than 33% ETc. In 2011, irrigation rate had minor or no effect on SWC, plant growth of mature plants, leaf gas exchange, and fruit number and yield. The no treatment effect observed for eggplant in 2011 was likely because study was conducted in a low field that remained moist most of the time, nullifying the treatment effects. Results suggested that eggplant may tolerate mild water stress, since plants irrigated at 67% ETc produced fruit yields similar to those of plants irrigated at 100% ETc or higher rates. Thus, there is a potential to save water by reducing current irrigation rates without negatively impacting fruit yields.
Juan Carlos Díaz-Pérez and Touria E. Eaton
Md J. Meagy, Touria E. Eaton and Allen V. Barker
Calcium-rich vegetables in the diet could ameliorate the potential for calcium (Ca) deficiency in human nutrition. This study investigated the prospect of increasing Ca density of lettuce (Lactuca sativa L.) through cultivar selection and nutrient management in a greenhouse. Eighteen lettuce cultivars including butterhead, romaine, and loose-leaf phenotypes of heritage and modern genetics were tested. Organic fertilizer (3N–0.7P–3.3K) and commercial conventional fertilizer (20N–4.4P–16.6K) factored with three Ca levels (50, 100, 200 mg·L−1 as CaCl2) were the fertilizer regimes. Calcium in whole shoots was analyzed by atomic absorption spectrometry of oven-ashed samples. Heritage cultivars had a significantly higher Ca concentration (1.93% dry weight) than modern cultivars (1.54%). Loose-leaf phenotypes had the highest Ca concentration (2.06%) followed by butterhead (1.66%) and romaine (1.49%). Accumulation of Ca was higher with the conventional fertilizer (1.90%) than with the organic fertilizer (1.58%). Elevated Ca level in the fertility regimes raised the Ca concentration in lettuce from 1.56% at 50 mg·L–1 to a mean of 1.82% at 100 mg·L−1 and 200 mg·L−1. Large differences in Ca concentration occurred among individual cultivars with ranges from 1.27% to 3.05%. ‘Salad Bowl’, ‘Red Deer Tongue’, ‘Buttercrunch’, and ‘Bronze Mignonette’ were the top in cultivar ranking with mean Ca concentration of 2.50%, whereas ‘Adriana’, ‘Australe’, ‘Coastal Star’, and ‘Forellenschluss’ were low accumulators with a mean of 1.33%. Head size of cultivars had no correlation with Ca concentration. This experiment indicates that selection of nutrient regimes and cultivars can be used to increase Ca accumulation in lettuce.
Touria E. Eaton, Douglas A. Cox and Allen V. Barker
Experiments were conducted to evaluate organic fertilizers in production of greenhouse-grown calibrachoa (Calibrachoa ×hybrida Llave & Lex) and marigold (Tagetes erecta L.) and nitrogen (N) leaching from containers during production. Calibrachoa was grown with five fertilizer treatments: one chemical, one organic-based, and three organic (liquid fish, oilseed extract, and a combination of oilseed extract and liquid fish). Marigold was grown with seven fertilizer treatments: one chemical and three organic (liquid fish, oilseed extract, and alfalfa pellets) used either alone or in combination. Chemical or organic-based fertilizers produced the best quality calibrachoa based on plant appearance and size. Liquid fish fertilizer produced healthy plants but smaller plants than those grown with chemical or organic-based fertilizers. Plants grown with oilseed extract were stunted and showed chlorosis. If oilseed extract was combined with liquid fish, the plants were similar to those grown with the chemical or organic-based fertilizers in size and quality. Chemical or liquid fish fertilizers produced the highest quality marigold based on plant appearance. Plants fertilized with alfalfa pellets were sparse and pale green. Oilseed extract produced the poorest growth and quality. If oilseed extract was combined with liquid fish or alfalfa, marigold plants were close in size and development to chemical-fertilized plants without nutrient deficiency and with some enhancement of nutrient levels in the leaves. The combination of alfalfa and liquid fish produced similar results. The highest N leaching resulted from plants fertilized by liquid fish, mostly in the form of ammonium nitrogen (NH4-N). Combining liquid fish with alfalfa or oilseed extract reduced the amount of N leached from the pots. The results suggest that organic fertilizers can be used successfully to grow commercial greenhouse crops but should be combined for good plant quality and environmental sustainability.