With freshwater supplies dwindling and sea levels rising, irrigation water for crops can become salinized. Therefore, salt-tolerant genotypes of food crops are needed. Here, we tested genotypes of Brassica juncea (brown mustard), a widely grown and consumed leafy green that has mineral and nutrient rich leaves and is also an important oil-seed crop, for their salt tolerance. Experiments were conducted to evaluate the performance of three mustard genotypes (var. ‘Florida Broadleaf’, ‘Carolina Broadleaf’, and ‘Southern Giant Curl’) grown in nutrient film-technique (NFT) hydroponic systems under varying salinity treatments. Five synthetic seawater dilutions (15, 22.5, 30, 37.5, and 45% Instant Ocean at approximately 10, 13.5, 17, 21, 24.5 dS/m conductivity, respectively) with added fertilizer (Masterblend 20-20-20 at approx. 1.5 dS/m) were compared to a control (fertilizer only at approx. 1.5 dS/m) to identify the optimal salinity range for vegetative production over 6 weeks after seeding. Two different production systems were used to evaluate the genotypes: production-scale NFT systems in a greenhouse in Citra, FL, and lab-scale tabletop NFT systems in an environmentally controlled room. In the greenhouse setting, plants were destructively harvested at 7 day intervals to gather growth over time, while in the lab setting, plants were harvested once at the end of the experiment to calculate the biomass and growth along with water and nutrient use efficiencies per genotype. Preliminary findings suggest that yields and water use efficiencies were improved at a 15% seawater dilution (approx. 10 dS/m) and showed a drop in biomass at higher seawater dilutions. The genotype ‘Florida Broadleaf’ demonstrated higher fresh biomass than either of the other genotypes with ‘Southern Giant Curl’ showing the most sensitivity to salt treatments in both the greenhouse and desktop systems. Data collected in these experiments will be used to construct a dynamic crop growth model for mustards that incorporates salinity to predict crop biomass. Crop models such as this could help inform plant breeders studying salt-tolerance and provide insights into yields and crop growth rates to agricultural producers farming in salt-afflicted soils or for use in saltwater hydroponics.
