Mineral Nutrition Status of Valencia Orange


However, the practice varied from a low of one-half ton of dolo-
mite per acre every third year to two tons of calcium limestone
per acre annually. Dolomite was used much more extensively
than calcium limestone. The latter was used in less than 15 per-
cent of the groves under study. Basic slag was also used in a
few scattered groves occasionally to supplement either dolomite
or calcium limestone.
 Spray and Dust Programs.-The spray and dust records from
145 groves indicated that the growers followed closely to the
recommendations listed in the Better Fruit Program (1). More
than half of the groves (56 percent) were sprayed with oil as
the summer scalicide. Parathion was used in 23 groves (16
percent). In 41 groves (28 percent) parathion and oil were
either applied in two separate applications or were combined
in a single application. There was a notable switch from para-
thion to oil in 1955 by a number of growers, probably because
of the inability of parathion to control mites and greasy spot.
A mixture of copper-oil applied during the regular melanose
spray in spring and followed with a summer scalicide was used
in 21 (14 percent) groves. The number of sulfur applications
for the control of rust mite varied from two to seven, with 48
percent of the groves receiving four applications a year. Two
and three applications of sulfur were made to 26 (18 percent)
and 33 (23 percent) of the groves, respectively, while 13 groves
(9 percent) were sprayed or dusted five times a year. There
were three (2 percent) groves that received six to seven sulfur
applications in 1955. Almost without exception one application
of DN (dinitro-o-cyclohexylphenol), used either alone or in com-
bination with wettable sulfur, was made in the fall for control of
mites. Two applications of DN were used in a small number of
groves. Aramite, Ovex and Systox were used in about 5 percent
of the groves during 1955. The records also showed that ap-
proximately 10 percent of the groves used concentrated spray
in 1955.
 Irrigation.-Approximately 75 percent of the groves under
study had facilities for irrigation. However, only one-half of
the groves were irrigated in the spring of 1955 despite the below-
normal rainfall in all the areas studied (3). The annual rainfall
for the several years preceding 1955 was "adequate," which may
have influenced the thinking of some of the growers as to the im-
portance of irrigation. The quantity of water applied varied
from one to 15 inches with the majority of the groves receiving