Soil applications of sulfureous compounds to control tipburn of head lettuce in the field
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Different levels of sulfureous compounds were applied to the soil before sowing or four to six weeks after sowing seeds of head lettuce (Lactuca sativa var.capitata L.) in five field plots throughout Arizona during 1979 and 1983. Plants were rated for tipburn incidence at harvest. Tipburn severity values were consistently lower in cultivars, Calmar, Vanguard and Empire and higher in cultivar Green bud in treated plots compared to non-treated plots. However, disease severity ratings in treated and non-treated plots were not significantly different at the 5% level.
Attempts to control lettuce tipburn by foliar and soil application of calcium salts have been successful in the greenhouse and in the laboratory3, 6, 7, but not in the field1, 2, 4.
Therefore, we undertook the present study to determine if the disease can be managed by soil application of sulfureous compounds. Our rational for using sulfureous compounds was based on the assumption that these compounds may convert a portion of the relatively water insoluble calcium carbonate (present in large quantities in the calcereous soils of Arizona and California) into more water soluble calcium sulfate by causing a slight drop in soil pH. Moreover, different formulations of sulfureous compounds, including those used in this study, are being used by some lettuce growers as soil conditioners and fertilizers.
Key wordsCalcium deficiency Control Lettuce tipburn
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