Seasonal Changes in Growth, Nitrogen Nutrition, and Yield of Hydroponic Lettuce

Abstract

The effect of different nitrogen (N) concentrations on growth changes, leaf N concentration and accumulation patterns, N nutrition index (NNI), fresh weight yield, and N use efficiency (NUE) was determined for lettuce grown over three consecutive seasons (fall, winter, and spring) in a recirculating hydroponic system, under unheated and naturally lit hoop house in Uvalde, TX. The lettuce cultivars Buttercrunch, Dragoon, and Sparx were grown at six N concentrations, initially 100, 150, 200, 250, 300, and 400 mg · L L1 using a nutrient film technique (NFT). Leaf number, accumulated dry weight (DW) and N, and leaf area index (LAI) followed a logistic trend over time, characterized by a slow increase during early growth followed by a linear increase to a maximum. By contrast, plant total N concentrations were the highest at early stage and decreased slightly over time. Effect of season and cultivar on these growth traits was more pronounced than that of the N concentrations. Averaged across cultivar and N concentrations, DW in spring was 73% and 34% greater than that in fall and winter, respectively. At each sampling date, there were linear, quadratic, or cubic effects of N concentrations on each of these variables. The cultivar Sparx was the most productive, with 63% and 32% higher fresh weight yield in fall, 145% and 114% in spring, than 'Buttercrunch' and 'Dragoon', respectively. Increasing nutrient solution N concentrations from 100 to 400 mg · L L1 increased the yield from 5.9 to 6.7 kg · m L2 in fall, 8.1 to 10.7 kg · m L2 in winter, and 10.3 to 12.6 kg · m L2 in spring. The NUE was the highest at the lowest N concentration (100 mg · L L1 ) and decreased with increasing N concentrations. The NNI during mid-to late-growth stages was near or greater than one, even at the lowest N. These results demonstrated that N concentrations of 100-150 mg · L L1 maximized the growth and yield of hydroponically grown lettuce.

Implication of quantifying nitrate utilization and CO2 assimilation of Brassica napus plantlets in vitro under variable ammonium/nitrate ratios

“…Generally, an excessive nitrogen supply is usually accompanied by low nitrogen use efficiency [ 36 , 37 ]. As shown in Table 3 , the nitrate use efficiency for new C input derived from the CO 2 assimilation (as indicated by the C C /N N ratio) was the lowest for Bn plantlets when the nitrate concentration increased to 40 mM.…”

“…Hence, the nitrate/ammonium use efficiency for new C input derived from CO 2 assimilation/sucrose utilization can be represented by the corresponding C/N ratio for Bn plantlets [9]. Generally, an excessive nitrogen supply is usually accompanied by low nitrogen use efficiency [36,37]. As shown in Table 3, the nitrate use efficiency for new C input derived from the CO 2 assimilation (as indicated by the C C /N N ratio) was the lowest for Bn plantlets when the nitrate concentration increased to 40 mM.…”

Integration of algae treatment with hydroponic crop waste to reduce impact of nutrient waste streams

“…Where data exists regarding CEA systems, it is usually highly bespoke to the system design and conditions of the experiment, thus direct comparisons are difficult to make. Studies carried out on salad crops in CEA systems have shown a wide range of N‐NUEs, covering two orders of magnitude (2%–104%) (e.g., Consentino et al, 2022; Djidonou & Leskovar, 2019; Pennisi et al, 2019; Santamaria et al, 2002; Yang & Kim, 2020; Wang et al, 2021) (Table 4). Data are more difficult to find for other elements to make comparisons, which are poorly represented in literature.…”

Evaluating the Use of Biostimulants for Indoor Hydroponic Lettuce Production

“…Correspondingly, others have shown that phytotoxicity reduces height and biomass production of hydroponic lettuce (Hoque et al, 2007). Further, according to Djidonou and Leskovar (2019), nutrient requirements of lettuce can be cultivar specific. This could explain the fact that leaf area and shoot FW of 'Monte Carlo' were not negatively affected by SE-2.…”