Florida Agricultural Experiment Station


sulfate per acre in the fertilizer, the first year, serves as an
inexpensive insurance against zinc deficiency. In subsequent
years 10 to 15 pounds per acre should be sufficient. As an
alternative procedure, zinc sulfate (89%) also can be supplied
with the first few bordeaux sprays, at the rate of 2 pounds
per 50 gallons of spray solution. Zinc deficiency has not been
definitely observed with celery on these soils, although there
has appeared to be some response to added zinc, and the response
to zinc of some other crops, such as beans, peas, cabbage, and
potatoes (6) has been quite marked.
 The use of copper is not such a problem with celery, inasmuch
as copper is the normal base for bordeaux sprays. However,
work with copper as a plant nutrient has indicated that it must
be present in the soil for benefit to the crop. The first year
that celery is grown on an area it is well to add some snow-form
bluestone (copper sulfate) along with the fertilizer. One
hundred pounds to the acre should suffice. For subsequent
crops the copper added in the bordeaux sprays will leave suffi-
cient residue in the soil and additional copper need not be added.
 Boron is still something of an unknown quantity on Ever-
glades soils where celery is concerned. In other sections of
the state (2) boron deficiency is known to develop as "cracked-
stem" disease, but little celery showing these symptoms has
been reported in the Everglades. Plants require boron in very
small quantities, and since it is known that many fertilizer
materials, such as natural nitrate of soda, triple superphosphate,
and most organic fertilizers (1) contain small amounts of boron,
when these ingredients are used in the fertilizer there is little
possibility of boron deficiency symptoms appearing. When
synthetic fertilizers are used exclusively in mixing the fertilizer
it might be well to add 10 to 15 pounds of borax per ton of
fertilizer as an insurance against deficiency of boron. Large
amounts of borax will prove toxic to plants, and are very
dangerous.
 According to present knowledge no other trace elements need
be added to these soils. If others are required, it is probable
that they are present in sufficient quantity as impurities in the
fertilizer materials commonly used. With respect to magnesium,
calcium and iron, there seems to be a sufficiency of these ma-
terials present in these soils natively, at least for several years'
cropping. It is recommended that no further supply of any
of these three be added.