Cucumber Plant Growth and Fruit Yield as Affected by 6-Benzyladenine and Magnesium Sulfate

Cucumber (Cucumis sativus) is an important vegetable crop in Georgia, with a surface of 1,700 ha and a farmgate value of $41 M.  Cucumber is exposed to heat stress conditions that affect fruit quality and fruit yield.  Crop biostimulants have been shown to increase crop yield and quality under adverse environmental conditions. Benzyladenine (BA) is a cytokinin used for fruit thinning in apples and other fruit trees. Objective was to determine the effects of rate of 6- BA alone or in combination with magnesium sulfate on chlorophyll SPAD values, plant growth, leaf gas exchange, leaf fluorescence, and fruit yield in cucumber. Experiment conducted at the Horticulture Farm, Tifton, Georgia, University of Georgia, during fall season of 2010.  Soil is loamy sand, with a pH of about 6.5. Cucumber (‘Dasher II’) was direct-seeded on 23 Aug. on raised beds (on 1.8 m centers).  Plants were established using 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 white plastic mulch.  One drip tape line was placed 2-3 cm deep into soil in the center of the bed. Experimental design was a randomized complete block with six replications and six treatments [three 6-BA (MaxCel^®) rates (0, 20 and 60 ppm) x two rates of magnesium sulfate (0 and 136 kg/ha)]. Benzyladenine was associated with reductions in chlorophyll SPAD values, particularly at high BA rate.  Benzyladenine had no effect on leaf gas exchange, leaf fluorescence and marketable yield. Benzyladenine-treated plants showed delayed fruit production and enhanced vegetative top growth.  Magnesium sulfate had no significant effects on chlorophyll SPAD values, vegetative top growth, leaf gas exchange, leaf fluorescence, or fruit yields.