Interaction Between Nutrient Source and Growing Substrate on the Yield of Beetroot in NFT Hydroponic Culture

Interaction Between Nutrient Source and Growing Substrate on the Yield of Beetroot in NFT Hydroponic Culture

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.