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James M. Spiers and John H. Braswell

Leaf concentrations of N, P, K, Fe, and Mn in `Sterling' muscadine grapes (Vitis rotundifolia Michaux) grown for 2 years in sand culture were not influenced by different N fertilizer sources. Leaf Zn and Cu were higher in plants receiving N as NH4NO3 rather than as (NH4)2SO4. Growth was greatest in plants fertilized with NH4NO3 compared to those with either (NH4)2SO4 or NaNO3 fertilization. Leaf Ca, Mg, Mn, and Cu content decreased linearly and leaf N increased linearly as N fertilizer rates were raised from 1.8 to 16.1 mM. Plant growth was a positively correlated with leaf N but was negatively correlated with leaf Ca, Mg, and Mn content. Percent Mg in the leaves was reduced when N levels, regardless of N source, were raised from the low (1.8 mM) to middle (5.4 mM) rate. High leaf N levels were correlated with lower Ca and Mg in the leaves, indicating a possible relationship between N fertilization and the late-season Mg deficiency often observed in muscadine grapes.

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James M. Spiers and John H. Braswell

Two-year studies were conducted on 4- to 6-year-old rabbiteye blueberry (Vacciniun ashei Reade) plants grown on a high (6.6) pH soil and irrigated regularly with water containing moderate amounts of Na and Ca (32 and 15 ppm, respectively). In one study, various levels (0, 280, 560, and 1120 kg·ha-1) of elemental S were applied in a single annual application. In another study, a single level (1120 kg·ha-1) of S was applied annually in either one, two, or four applications. Applications of S at up to 1120 kg·ha-1 were not detrimental to plant vigor of rabbiteye blueberries. Soil pH decreased with successively higher levels of applied S. Leaf P, K, and Mn contents were higher and soil pH was lower with single compared with multiple applications of S. Soil K, Ca, Mg, and S levels were negatively correlated with plant growth. Amounts up to 1120 kg·ha-1 of applied elemental S were not sufficient to lower soil pH to a level desirable for rabbiteye blueberry production when the soil was irrigated 7 months·year-1 with water containing moderate amounts of Na.

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James M. Spiers and John H. Braswell

The effects of varying N, Ca, and Mg fertilization levels on plant growth and leaf elemental content of `Sterling' muscadine grapes (Vitis rotundifolia Michaux) were studied in a 2 year sand culture experiment. Increased N levels reduced leaf K, Ca, and Mn and increased leaf N and P concentrations plus plant growth. Calcium fertilization increased leaf Ca, decreased leaf Mg, but did not affect plant growth. Mg fertilization reduced leaf K and Ca and increased leaf Mg plus plant growth. Visual symptoms, assumed to be Mg deficiencies, were decreased by Mg fertilization and highly correlated to leaf Mg content. Plants which received the highest Ca fertilizer level had fewer deficiency symptoms when treated with the highest rate of N. Calcium fertilization tended to slow both Mg uptake and deficiency symptoms reductions caused by increases in levels of applied Mg. Growth of `Sterling' muscadine plants was positively correlated to leaf N and Mg and negatively related to leaf K, Ca, Mn, Zn, and Cu concentrations.