ASHS 2015 Annual Conference

Red Giant Mustard (Brassica juncea) and Mizuna (Brassica rapa var. nipposinica) plants were grown at the University of Minnesota St. Paul Campus (St. Paul, MN) in a greenhouse from December to February under an 18-hour photoperiod (natural daylight plus 50 μmol·m^-2·s^-1 high pressure sodium lighting from 0800 to 0200 HR) and a 24/13 °C day/night temperature. Plants were grown using five different fertility treatments, including four organic treatments and one conventional control (Cal Mag 15-5-15 in SunGro LC8©media), to determine their effects on Red Giant Mustard and Mizuna growth and nutrient content. Biomass yield, vitamin C and total dietary fiber varied with fertility treatment. Total dietary fiber and vitamin C levels were measured from tissue frozen at –80 °C.  Foliar nutrients (P, K, Ca, Mg, Fe, Mn, B, Cu) were determined using an inductively-coupled plasma spectrophotometer. The experiment was replicated four times in time and the experiment was duplicated. The poultry litter treatment with Sunshine Natural and Organic Planting Mix© had the highest vitamin C content in both crops (16.0 mg/100 g in Mizuna and 20.8 mg/100 g in Red Giant Mustard). Both crops had similar vitamin C responses to the five fertility treatments, but were not associated with biomass yield, and there were no positive correlations between increases or decreases in biomass yield in relation to vitamin C content. Total dietary fiber ranged from 2–4 g/100 g per sample, indicating both crops can contribute a significant fiber to the diet, compared with other leafy vegetables, such as Romaine or Iceberg lettuce. Results indicated that fertility plays a role in vitamin C synthesis and/or accumulation, both crops can contribute a moderate amount of dietary fiber to the diet, and biomass yield may not be associated with changes in vitamin C content.   Fertility effects on leaf mineral content will also be discussed.