The 2009 ASHS Annual Conference

Jonathan N. Egilla

Lincoln University Cooperative Research Program, 904 Chestnut St., Jefferson City, MO 65102-0029.

Abstract. The effect of mineral nutrient (fertilizer) and growing substrate source on the yield of beetroot (Beta vulgaris ‘Bulls Blood’) was evaluated in a closed, nutrient recirculating ‘Nutrient Film Technique’ (NFT) hydroponic system. Seedlings raised in 1-inch oasis or rockwool cubes were transferred into rows (28 cm apart) of PVC Hydro-Troughs with 4.45 cm diameter holes at 20 cm spacing (along the row) at the one true-leaf stage. Seedlings were grown until harvesting, either with Peters Excel-CAL-MAG^® (CAL-MAG; J. R. Peters, Inc., Allentown, PA), or All-Purpose Hydroponic Nutrient^® (APHN; Hollister's Hydroponics, Grand Junction, CO), consisting of 15-5-15, and 9-4-15, respectively as percent N-P₂O₅-K₂O. Nitrogen (N) concentration in nutrient solution was 200 mg/liter with CAL-MAG, and at manufacturer's recommended concentration (1 lb fertilizer/100 gallon of water [108 mg N/liter]) with APHN. CAL-MAG increased fresh and dry weight yield of beetroot 2-3 fold compared with APHN. Fertilizer × substrate interaction was significant (P ≤ 0.05) for all the yield parameters measured except root dry weight (RDW) and root:leaf ratio (RLR). With CAL-MAG, components of yield (except RDW and RLR) were increased significantly (P ≤ 0.0003) in rockwool compared with oasis cube. However, with APHN, only leaf fresh weight was significantly higher (P = 0.0492) in rockwool than oasis cube. While fertilizer had no effect on leaf total N and potassium, CAL-MAG significantly increased the concentration of calcium (Ca), magnesium, and sulfur (P <0.0001; P = 0.0069 and P = 0.0246, respectively) over APHN, but phosphorus was significantly higher (P = 0.0403) with APHN. Of the micronutrients, leaf boron (B) and molybdenum (Mo) (P < 0.0001), as well as aluminum (Al; P = 0.0403) concentration varied significantly with fertilizer, and fertilizer × substrate interaction was significant (P ≤ 0.05) for B and Al. With the exception of Ca and B (respectively, 66–75% and 52–72% below the sufficiency range), leaf concentration of essential nutrients were sufficient for beetroot, regardless of fertilizer. These trends suggest that tissue Ca and B concentration contributed to the observed yield response of beetroot in this study.