Bell Pepper Plant Growth and Fruit Yield as Affected by S-ABA Concentration and Water Application Rate

In the state of Georgia, bell pepper (Capsicum annum L.) has a surface of 2,400 ha and a farmgate value of $78 M.  Bell pepper is exposed to heat stress conditions that affect fruit quality and fruit yield.  Crop biostimulants have shown to increase crop yield and quality under adverse environmental conditions. Abscisic acid (ABA) has many roles in plants but it is primarily associated with stress responses. Objective was to determine the effects of S-ABA concentration and water application rate on plant physiology and growth, and fruit yield in field-grown plants.  Experiment was conducted at the Horticulture Farm, Tifton, Georgia, University of Georgia, during the spring of 2012.  Soil is loamy sand, with a pH of about 6.5. Experimental design was a randomized complete block with a factorial arrangement and eight treatment combinations [4 S-ABA (VBC-30151, Valent BioSciences) levels (0, 250, 500, 1000 ppm) x 2 water application volumes (250 and 1000 mL/m² of tray)]. Bell pepper (‘Colossal’) was planted to the field on 9 Apr. 2012 on raised beds (on 1.8 m centers); two rows per bed (36 cm apart) with a distance of 30 cm between plants within the row.  Beds were covered with 1.5 m wide low density polyethylene black plastic mulch; one drip tape line was placed 2-3 cm deep into the soil in the center of the bed.  The field was fertilized before planting with 672 kg/ha of 10N-10P₂O₅-10K₂O fertilizer.  After planting, N and K₂O were applied weekly through the drip tape.  Total amount of N and K₂O applied were 261 and 304 kg/ha, respectively.  Plants were irrigated with an amount of water equivalent to 100% crop evapotranspiration (ETc). Weather data (air temperature and ETo) were obtained from a nearby Univ. of Georgia weather station (< 300 m).  Bell pepper plant growth, measured as stem diameter and plant height decreased with increased concentrations of S-ABA and increased water application rate. Leaf net photosynthesis and stomatal conductance of mature plants were not significantly affected by S-ABA concentration; they were increased when treated with the high water application rate. Despite the effects on plant growth, no significant effects of S-ABA concentration or water application rate on fruit number or fruit yield were found.