Page 19 - Volume 4, Issue 1, January 2011
Basic HTML Version
© Benaki Phytopathological Institute
Response of young olive trees to nitrogen
17
the growth of old mature olive trees (4, 13).
However, it has also been reported that the
optimum leaf [N] is higher in young than in
mature olive trees (16). Furthermore, Gon-
zalez
et al
. (10, 11, 12) found that the yield of
mature olive trees was reduced when leaf [N]
was < 1.95%.
The results of the present study also
showed that the increased leaf DWT was
accompanied by a significant (P<0.01) in-
creased soil [NO
3
-N] due to split soil N fer-
tilization, nitrification and addition of NO
3
-N
with irrigation (Fig. 6). After the last applica-
tion of soil N fertilizer (65 DAF), big differenc-
es (P<0.05) in soil [NO
3
-N] were found among
the treatments. The soil [NO
3
-N] in treat-
ments N
3
and N
4
was very high (>100 mg/
kgDWT), whereas in the other treatments it
was between 20 and 50 mg/kg DWT. To es-
timate the threshold soil [NO
3
-N] (25 mg/kg
DWT) for maximum growth of young olive
trees, the relationship between leaf DWT
and soil [NO
3
-N] was used (Fig. 7). The rela-
tionship between the mean leaf DWT and
the mean soil [NO
3
-N] during the course of
the experiment was curvilinear and it was
described by the following equation:
Leaf DWT = a+b*r
[NO
3
-N]
+c
[NO
3
-N]
where, a, b, r and c are the coefficients de-
rived from the statistical analysis (Table 2).
Figure 4.
Effects of N fertilization on the ratio of
leaves+shoots+stems dry weight (DWT) (g) : root length (m)
of one-year-old olive trees. Soil N fertilization rates: N
0
: 0, N
1
:
0.95, N
2
: 1.90, N
3
: 3.80, N
4
: 6.25 g N at three monthly applica-
tions. Foliar treatment N
f
: 0.3 g/l of 21-21-21 (N-P-K) soluble
fertilizer at six monthly applications. Means followed by a dif-
ferent letter are significantly different at P<0.05 level. Means
separation calculated by the Duncan test.
N fertilizer treatments
Leaf+stem+shoot DWT (g) : root length (m)
Figure 5.
Changes in the leaf [N] (%) during the growth of
one-year-old olive trees. DAF: days after first fertilization. Soil
N fertilization rates: N
0
: 0 (
■-■
), N
1
: 0.95 (
▲-▲
), N
2
: 1.90 (
▼-
▼
), N
3
: 3.80 (
♦-♦
)
, N
4
: 6.25 (
●-●
) g N at three monthly ap-
plications. Foliar treatment N
f
: 0.3 g/lof 21-21-21 (N-P-K) solu-
ble fertilizer at six monthly applications. Bars: Least significant
difference (LSD) at each harvest.
N (%)
DAF
Figure 6.
Changes in the soil [NO
3
-N] (mg kg
-1
DWT) during
the growth of one-year-old olive trees. DAF: days after first
fertilization. Soil N fertilization rates: N
0
: 0 (
■-■
), N
1
: 0.95
(
▲-▲
), N
2
: 1.90 (
▼-▼
), N
3
: 3.80 (
♦-♦
)
, N
4
: 6.25 (
●-●
) g N at
three monthly applications. Foliar treatment N
f
(*-*): 0.3 g/lof
21-21-21 (N-P-K) soluble fertilizer at six monthly applications.
Bars: Least significant difference (LSD) at each harvest.
NO
3
-N (mg/kg DWT)
DAF
