Florida Agricultural Experiment Stations


magnesium content in both leaf and fruit showed a steady in-
crease from pH 4.8 to 5.9, and then gradually decreased as soil
pH continued to increase. It was pointed out in the previous
section that the quantity of water-soluble magnesium applied in
the fertilizer showed no significant effect in the magnesium con-
tent of leaf and fruit. Therefore, it seemed that dolomite ap-
plications have more influence on the magnesium content of leaf
and fruit than the water-soluble magnesium applied through
fertilizer.

 TABLE 19.-THE INFLUENCE OF DIFFERENT SOIL PH ON QUALITY AND
 MINERAL COMPOSITIONS OF LEAF, FRUIT AND SOIL.

Soil pH Rind Texture Groves Soluble Magnesium
 Groves Smooth Solids Leaf Fruit
Range No. % No. Brix % %
4.75-505 .. 2 45.5 2 12.18 0.322 0.097
5.05-5.35 9 42.9 11 11.71 0.367 0.103
5.35-5.65 .. 20 32.7 30 11.54 0.407 0.111
5.65-5.95 .. 44 27.5 62 11.39 0.446 0.114
5.95-6.25 .. 36 26.6 48 11.15 0.428 0.113
6.25-6.75 .. 6 24.8 8 11.15 0.410 0.108

Statistical I
 significance ** **


 Calcium is the predominating base in the soil colloidal com-
plex. Magnesium, though present in much smaller quantity, is
of equal importance. The amounts of exchangeable calcium and
magnesium found in the soil are closely correlated to the ex-
change capacity at approximately the same pH values (11). For
the same reason the extractable calcium and magnesium should
increase with pH of soil with similar exchange capacity. The
data presented in Table 20 represent the average values of ex-
tractable calcium and magnesium based on different pH ranges.
The data were further divided on the basis of groves that re-
ceived dolomite and those that used calcium limestone. Highly
significant differences in the extractable calcium content at dif-
ferent pH ranges were observed for groves using dolomite as
well as those using calcium limestone. The same was true also
of the extractable magnesium content for groves using dolomite,