With the object of finding the control measures for the magnesium deficiency of grape trees in sand dune region, comparison was made amoung magnesian limestone, fused phosphate, combined fertilizer and compost in the manurial value of magnesium for young grape trees (var. Delaware) from 1957 to 1958.
In early spring of 1957, experiment was set up with 5 plots constituted of Non-magnesium, Magnesian limestone, Fused phosphate, Combined fertilizer and Compost, and in next 1958, treatment and observation were continued with 3 plots of Magnesian limestone, Fused phosphate and Compost. In each plot, the nutrient elements were dressed as equally as possible in quantity and standard ratio of these elements was as follows ; N : 10, P_2O_5 : 5, K_2O : 7.5, CaO : 20 (1957) and 30 (1958). Therefore the ratio of MgO to N resulted not to be similar in each plot and the highest of it was 10 in the plot of Magnesian limeston. Then in any plots with the exception of Fused phosphate plot, super phosphate was used as the source of phosphate element.
The results are sumerized as follows ;
Non-magnesium caused serious magnesium deficiency and worse growth, and this fact showed the necessity of magnesium supply for grape trees in sand dune region. When magnesian limestone was applied, magnesium deficiency scarcely found and growth was better, but K content in leaves had a tendency to be lower. In the case of fused phosphate which was dressed according to the standardization of P_2O_5, magnesium deficiency could not be controled and growth was the worst and moreover, P content in leaves was the lowest of all. Dressing of combined fertilizer controled enough magnesium deficiency, and growth in this plot was the best next to compost. When compost was applied, growth was remarkably excellent, and content of each element (N, P, K, Ca) in leaves was higher than in any other plots, but Mg content alone was low and deficiency symptom was severe next to Non-magnesium plot. It means that compost application for grape trees in this region is much effective for the growth but not sufficient for supplying magnesium in order to satisfy the demand of the plants.