A Rapid Test for Possible Excesses of

 Copper in Sandy Soils

 W. F. SPENCER 1

 It is known that applied copper is largely retained in sandy
soils and may exhibit beneficial or harmful properties, depend-
ing on the amount present in the soil. Soil analysis by Rogers
et al. (9) showed that the copper content of virgin soils was
usually less than 10 ppm, whereas cultivated soils contained as
high as 300 ppm Cu. Erwin (4) found that less than 1%C of
the added copper was leached from lysimeters filled with soil
during the nine months of his experiments. More recent work
by Reuther, Smith, and Specht (6, 7, 8) and Westgate (15)
verified the fact that copper accumulates in Florida soils. Thus,
it is possible to build up the copper content of the soil so that
it is not necessary to apply additional copper to meet the nu-
tritional requirements of citrus trees.
 It has been common practice in recent years to apply relatively
large amounts of copper to citrus grove soils. Thus, in some
groves such large accumulations of copper occur (7) as to be
potentially detrimental to citrus trees. Chapman and associates
(1) observed that slight excesses of copper induced iron chlorosis
in citrus plants growing in nutrient solutions. Reuther and Smith
(6) concluded that the level of soil copper in many mature
Florida citrus groves on acid sandy soil is approaching a point
where foliage chlorosis and damage to normal root development
is likely to occur if the soil is allowed to become too acid. Stewart
and Leonard (11) found that acid soil chlorosis of citrus can
be corrected by additions of an iron chelate (EDTA) to the soil.
 Excess copper has been found to be detrimental to other crops
also. Recent work by Westgate (15) indicates that residues
from copper sprays on celery and other crops have accumulated
in toxic amounts in the surface layer of old celery fields in the
Sanford area. Steenbjerg (10) found that the amount of copper
available to grasses and cultivated plants was at a minimum
at pH 5.5 to 6.5 and that organically combined copper was avail-
able at various pH values depending upon the combination in
which it occurred. Reuther and Smith (6) and Westgate (15)
 1The author wishes to thank Dr. Herman J. Reitz for help in preparing
the manuscript.