Florida Agricultural Experiment Station


than the actual available phosphate content. The basic slags
also contain from 1 to 3%c of manganese oxides, and since
manganese is also very low in these soils it is impossible to
tell how much of the yield difference is due to the source of
phosphate and how much to the various trace elements present
in the slag. In general, basic slag is well suited to unburned
soils and less suited for use on alkaline soils. Should home
mixing of fertilizer be practiced, ammonia fertilizers should
not be mixed with basic slags, or some of the ammonia will
be lost.
 The superphosphates, "single" or "triple", can be used more or
less interchangeably. Triple superphosphate is slightly cheaper
per unit of P20s (4), and more economical, higher analysis fer-
tilizers can be mixed when this material is used. These are
probably the most satisfactory phosphatic materials on neutral
or alkaline soils, and they have proven very satisfactory on the
slightly acid soils of the Everglades Experiment Station. The
available phosphoric acid (P205) has a cost of 5.5c per pound
in 16% superphosphate, and of 5.1c per pound in 44% super-
phosphate, according to the State Chemist's report (4).



 500 -


 *CO I




 9% .-: 90
 o -


 No FfO C ; K:-. 18% k0


 Fig. 9.-The influence of different amounts of phosphate (POs) fertilizers on five-year
 average yields of marketable celery produced per acre on Area 2 at the Everglades Experiment
 Station. The different amounts of phosphate applied were tested at each of three levels of
 potash (KeO). The yield represented by the figures is given in terms of the number of
 field-trimmed crates produced per acre. (Yield data for the separate years for all of these
 comparisons are listed in Table 8 in the appendix.)

 Figure 9 represents the yields of marketable celery, in terms
 of the number of 70-pound field-trimmed crates per acre, pro-
 duced by using different quantities of superphosphate in the