Date palms are usually fertilized,
although in many cases only with nitrogen
(Nixon and Carpenter, 1978). Responses to
fertilization are inconsistent and probably
depend upon cultivar, soil type, and other
factors. For instance, in the United States,
Furr and Cook (1952) sampled ‘Deglet Noor’
and ‘Khadrawy’ and reported that N concentrations
were higher in leaves of fertilized
trees compared with nonfertilized trees.
However, there was not a consistent correlation
with yield either of fertilization or of leaf
N levels. There was an apparent weak
response from ‘Deglet Noor’, but none was
observed with ‘Khadrawy’. Labanauskas and
Nixon (1962) sampled healthy and declining
palms but noted no significant differences in
nutrient concentrations. The values reported
for most elements were lower than those
established for citrus. Date palm leaf nutrient
concentrations published from various countries
are inconsistent but generally have
shown low N concentrations compared with
other perennial crops. Interestingly, concentrations
from date palms grown in the United
States and receiving high levels of N have
consistently been lower than those reported
for date palms in the Middle East and North
Africa (Krueger, in press).