Abstract
The Mehlich-1 Mg soil test calibration and Mg fertilizer requirements were evaluated for cucumber grown on sandy soil. The experiment was conducted on a soil initially testing low in Mg (<20 mg-kg1 Mg). Soil samples were taken from the beds of each plot prior to Mg treatment application each season. Magnesium fertilizer for all treatments was incorporated into the soil before mulching. In spring 1997, treatments were 0, 17, 34, 67, and 134 kg-har1 Mg. For fall 1997, each spring treatment plot was split into four plots, each receiving either 0, 17, 34, or 67 kg.ha1 Mg. For spring 1998, each of the fall 1997 plots was split into six plots, each receiving either 0,11,22,34, 45, or 90 kg ha1 Mg. Plants were grown on raised beds that were fumigated with methyl bromide and mulched with polyethylene. 'Lightning' cucumber seeds were planted, and the crop was irrigated by drip irrigation using water that was softened with a household water softener to remove Mg. Harvested fruits were graded as marketable or cull, according to USDA standards. For spring 1997, Mg fertilizer treatments did not affect marketable yield, although yield was significantly affected by the initial Mg soil test index. In fall 1997, yield was improved by the first increment of Mg fertilizer, but the initial soil test index did not affect yield. In spring 1998, yield was not affected by Mg fertilizer treatments, but was affected by initial soil test index. Leaf Mg concentration at first bloom was not affected by Mg fertilizer treatment and was adequate. Leaf Mg concentration at harvest increased linearly with Mg fertilization in two out of three seasons. Fertilization with recommended rate of Mg resulted in leaf Mg concentrations in the adequate range. The inconsistent and unpredictable responses to Mg reflected the mobility of this element in sandy soils or that the native soil concentration of Mg was already near the critical level in the crop season. Under any soil test Mg situation in this study, the recommended amount of Mg was adequate for greatest yields.
