Potassium source and rate for polyethylene-mulched tomatoes
1997
Locascio, S.J. | Hochmuth, G.J. | Olson, S.M. | Hochmuth, R.C. | Csizinszky, A.A. | Shuler, K.D.
Tomato (Lycopersicon esculentum Mill.) was grown with polyethylene mulch at five locations during a total of nine seasons to evaluate the effects of K source and K rate on fruit yield and leaf K concentration with drip and subsurface irrigation K sources evaluated were KCl, K2SO4, and KNO3 and K rates varied from 0 to 400 kg.ha-1. Preplant soil K concentrations by Mehlich-1 extraction on the sandy soils and loamy sands used in the study varied from 12 mg.kg-1 (very low) to 60 mg.kg-1 (medium). In seven of the eight studies, K source did not significantly influence fruit yield or leaf K concentration In the other study with subsurface irrigation at Bradenton in Spring 1992, marketable yields were significantly higher with KNO3 than with KCl as the K source. Tomato fruit yield responded to the application of K in all studies. At Gainesville, Quince, and Live Oak, with drip irrigation on soils testing low to medium in K, maximum yields were produced with 75 to 150 kg.ha-1 K where the K was broadcast preplant. These rates were 25% to 30% higher than those predicted by soil test. At Bradenton and West Palm Beach on soils testing low to very low in K, where all or part of the K was applied in double bands on the bed shoulder with subsurface irrigation yield responses were obtained to 225 to 300 kg.ha-1 K. These rates exceeded the maximum recommended K rate of 150 kg.ha-1. Tomato leaf tissue K concentration increased linearly with increased rates of K application, but were not influenced by K source. These data suggest that the recommendation for K on soils testing low in K be increased from 150 to 210 kg.ha-1 and that this increase should suffice for tomatoes grown with either drip or subsurface irrigation.
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