Hydroponics has been an increasingly important field of vegetable production. However, a big issue with hydroponics is that certain crops can quickly accumulate high levels of nitrate-N (NO3 ± -N) from the hydroponic system. The objective of this research was to decrease NO3 accumulation and increase the nutritional value and yield of vegetable crops using lettuce and oilseed rape as a model under hydroponic production. In this study, two technologies were applied to leafy vegetable production: 1) using supplementary lighting (blue-violet diode) by manipulating illumination and 2) removing fertilization before harvest for a short term (3 or 5 days), thus providing a practical experiment for improving yield and edible qualities of hydroponic leaf vegetable production. Illumination was applied 4 hours a day (0500–0700 hr and 1700–1900 hr) during good weather, or 12 hours a day during bad weather with insufficient natural light (<2000 lux) during the autumn and winter seasons. Results showed that the lettuce cultivar Ou-Luo and the oilseed rape cultivar Ao-Guan Pakchoi had increased yield (50.0% and 88.3%, respectively), decreased NO3 content (26.3% and 30.8%, respectively), and increased total soluble solids (24.1% and 30.6%, respectively). The 5-day fertilizer-free treatment before harvest resulted in 19.2%, 6.4%, and 16.5% yield increases; and 26.0%, 24.3%, and 47.8% NO3 decreases in oilseed rape cultivar Ao-Guan Pakchoi and lettuce cultivars Da-Su-Sheng and Ou-Luo, respectively.
Jinghua Guo, Yan Yan, Lingdi Dong, Yonggang Jiao, Haizheng Xiong, Linqi Shi, Yu Tian, Yubo Yang, and Ainong Shi
Qirui Cui, Haizheng Xiong, Yufeng Yufeng, Stephen Eaton, Sora Imamura, Jossie Santamaria, Waltram Ravelombola, Richard Esten Mason, Lisa Wood, Leandro Angel Mozzoni, and Ainong Shi
Cowpea [Vigna unguiculate (L.) Walp.] is not only a healthy, nutritious, and versatile leguminous crop; it also has a relatively high adaptation to drought. Research has shown that cowpea lines have a high tolerance to drought, and many of them can survive more than 40 days under scorching and dry conditions. The cowpea (Southern pea) breeding program at the University of Arkansas has been active for more than 50 years and has produced more than 1000 advanced breeding lines. The purpose of this study was to evaluate the drought-tolerant ability in Arkansas cowpea lines and use the drought-tolerant lines in cowpea production or as parents in cowpea breeding. A total of 36 University of Arkansas breeding lines were used to screen drought tolerance at the seedling stage in this study. The experiment was conducted in the greenhouse using a randomized complete block design (RCBD) with two replicates, organized in a split-plot manner, where the drought treatment (drought and nondrought stress) as the main plot and the cowpea genotypes as the subplot. Drought stress was applied for 4 weeks, and three drought-tolerant–related traits were collected and analyzed. Results showed that cowpea breeding lines: ‘17-61’, ‘17-86’, ‘Early Scarlet’, and ‘ARBlackeye #1’ were found to be drought tolerant.