Mineral Nutrition Status of Valencia Orange


As a result, the potassium contents of leaf and fruit may be rela-
tively low because of the suppressing effects of nitrogen on po-
tassium. An erroneous conclusion may then be drawn that high
rates of potassium application had no effect on the potassium
contents of leaf and fruit. However, when the rates of both ni-
trogen and potassium are taken into consideration, the potassium
contents of leaf and fruit are significantly different at various
levels of application.
 The fact that the quantity of water-soluble magnesium ap-
plied in the fertilizer was not related to fruit production, quality
or the magnesium content of leaf, fruit and soil would seem to in-
dicate that it was not the only source of magnesium. Records
showed that approximately 85 percent of the groves used dolo-
mite for control of soil acidity. This led to the belief that dol-
omite may be an important source of magnesium. A compari-
son of the average magnesium content of leaf, fruit and soil
between groves using calcium limestone and dolomite substanti-
ated the belief. On the average, less water-soluble magnesium
was applied to groves which used dolomite than those using cal-
cium limestone and yet, the average magnesium content of leaf
and fruit was higher for the former. The difference in the ex-
tractable magnesium of the soil was negligible, as shown in
Table 18.

TABLE 18.-A COMPARISON OF THE AVERAGE MAGNESIUM CONTENT OF LEAF,
FRUIT AND SOIL IN GROVES LIMED WITH DOLOMITE AND CALCIUM LIMESTONE.

Material Percent Avg. MgO" Magnesium Content
 Groves Applied Leaf Fruit Soil
 Percent lbs./A. Percent Percent lbs./A.
Calcium
 Limestone ........ 15 111 0.390 0.109 92
Dolomite .............. 85 89 0.428 0.114 89

 a. Water-soluble magnesium applied as magnesium sulfate.

 INFLUENCE OF SOIL REACTION
 The range of soil pH covered in the present study did not
correlate directly with fruit production. Characteristics that
were related to soil pH are summarized in Table 19. Only two
characteristics of fruit quality were related to soil reaction.
 Fruits of smoother rind and higher solids were produced on
soils with lower pH. Magnesium was the only element studied
for which leaf or fruit analysis was related to soil reaction. The