Experiments were conducted in the spring of 1990 at Quincy and Live Oak, Florida and 1991 in Quincy to study the effect of 3 K sources (KCl, K2SO4 and KNO3) and 5 K rates (0, 75, 150, 225 and 300 kg ha-1) of yield of `Sunny' tomatoes. Preplant soil test K values were 37 and 54 ppm in 1990, respectively, and 44 ppm in 1991. These K concentrations are considered medium (36-60) for Florida mineral soils. K source had no effect on yield, fruit weight or percent marketable fruit in all studies. In 1990, total yields, yield of extra large (> 7.0 cm) fruit and percent marketable fruit were increased with application of 75 kg ha-1 of K but there was no further response to applied K at both locations. In 1991, total yield increased with applied K up to 150 kg ha-1 then decreased. Fruit size and percent marketable fruit increase with 75 kg ha-1 of K but no further response occurred. There was no interaction of K source and K rate.
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