Mineral Nutrition Status of Valencia Orange


but in groves receiving calcium limestone the level of signifi-
cance between exchangeable magnesium and soil reaction reached
only the 5 percent level.

 TABLE 20.-RELATION BETWEEN SOIL REACTION AND EXTRACTABLE
 CALCIUM AND MAGNESIUM CONTENTS.

Soil Dolomite Limestone
Reaction Groves Groves
 Extractable Extractable
 Calcium Magnesium Calcium Magnesium
 pH No o. Lbs A. Lbs.A. No. Lbs.A. Lbs./A.
4.75-5.05 2 263 34 1 365 39
5.05-5.35 10 370 49 3 444 72
5.35-5.65 28 403 66 6 525 79
5.65-5.95 54 606 89 8 798 90
5.95-6.25 40 754 112 14 965 103
6.25-6.75 9 1319 109 2 1750 124

Statistical
 significance ...... ** -:* *

 The extractable calcium was consistently higher in groves
which received calcium limestone when compared to those using
dolomite at the same pH range. Higher solubility of residual cal-
cium carbonate compared to dolomite by the extracting solution
may have been a factor.
 Peech and Young (11) contended that a calcium-magnesium
ratio between 8 and 10 to 1 was desirable and necessary to pre-
vent magnesium deficiency. Such a ratio was found in all the
pH ranges except in groves where the pH was 6.3 or above. The
average calcium-to-magnesium ratio in this range was 12 to 1
for groves receiving dolomite and 14 to 1 for those using calcium
limestone and showed no attending magnesium deficiency.

 INFLUENCE OF COPPER IN SOIL
 The effects of soil copper content on the characteristics meas-
ured are summarized in Table 21. Fruit quality was not affected
by the copper content in soil. Fruit production increased with
soil copper content. It was highly doubtful that soil copper con-
tent caused increase in fruit production. Increase in the nitro-
gen applied undoubtedly contributed to higher yield. The par-
allel increase in the available soil phosphorus and copper would