Hellenic Plant Protection Journal
1
: 26-31, 2008
Effect of different rates of nitrogen application on the
concentration of micronutrients in lettuce and spinach plants
A. Assimakopoulou
1,2
, Y.E. Troyanos
1
and Ch. Tsougrianis
2
Summary
The effects of several nitrogen application rates on Fe, Mn, Zn and Cu concentration
in lettuce and spinach plants were studied in three experiments. The applied nitrogen treatments
were: seven concentrations of nitrate nitrogen (N
1
:0.1, N
2
:0.5, N
3
:1.0, N
4
:2.0, N
5
:4.0, N
6
:7.0, N
7
:14.0
mM N) for Butterhead lettuce, six (N
1
:1.0, N
2
:3.0, N
3
:6.0, N
4
:10.0, N
5
:16.0, N
6
:22.0 mM N) for spinach,
in hydroponics, and six nitrogen fertilization rates (N
1
:0, N
2
:45, N
3
:90, N
4
:135, N
5
:180, N
6
:225 kg Ν/
ha) for Romaine lettuce in the field. The growth of Butterhead lettuce and spinach plants in hy-
droponics was increased by increasing nitrogen supply; foliage Mn, Zn and Cu concentration was
higher at the low nitrogen levels whereas at high N supply a gradual reduction in the relevant mi-
cronutrient concentration occurred. In the field, there was a significant increase on lettuce plant
fresh weight up to the level Ν
5
with increasing the quantity of N fertilizer whereas at the highest ni-
trogen level N
6
, a significant reduction of plant growth occurred; a significant positive correlation
was found between the foliage fresh weight and Zn and Cu concentration. In all the experiments,
no correlation was found between Ν application and foliage Fe concentration.
Additional keywords:
N fertilization, N supply, growth, Fe, Mn, Zn, Cu, nutrient interactions
Introduction
The contents of nutrient elements in
leafy vegetables are important to human
health, mainly for people in developing
world. Besides, lettuce and spinach as di-
etetic food has long been the object of
many investigations. It is well known that
fertilization practices can have significant
effects on the accumulation of micronu-
trients on the edible plant products (15).
Furthermore, the interactions among nu-
trients and/or growth effects caused by
increased supply of a nutrient could affect
accumulation of micronutrients in plants.
The interactions among nutrients are
often complex and occur when the up-
take of one element affects the uptake
and assimilation of another and they are
expressed in different ways, including up-
take phenomena and biochemical reac-
tions. A nutrient may interact simultane-
ously with more than one nutrient; this
may induce deficiencies, toxicities and/
or modified nutrient composition. In crop
plants, the nutrient interactions are gener-
ally measured in terms of uptake and “con-
centration effects” due to modified plant
growth. Better understanding of nutrient
interactions may be useful in understand-
ing the importance of balanced supply of
nutrients and consequently the improve-
ment in plant growth and yields (1).
Nitrogen may interact simultaneous-
ly with more than one nutrient. It is of
fundamental importance in order to im-
prove plant growth and development, to
understand the interactions of nitrogen
with other nutrients. The quantity and the
1
Laboratory of Non Parasitic Diseases, Benaki Phyto-
pathological Institute, 8 St. Delta str., GR-145 61 Kifis-
sia (Athens), Greece
2
District Laboratory of Agricultural Advisory Services
and Fertilizer Analyses, GR-204 00 Xylokastro, Greece
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