Growth and yield of garden rocket (Eruca sativa. Mill.) affected by nitrogen and potassium fertilization

Abstract

We studied the effect of differentiated nitrogen-potassium fertilization upon the growth, yield and chemical composition of garden rocket leaves grown in unheated greenhouse in autumn. Two nitrogen doses were applied (0.3 and 0.6 g dm -3) in the form of calcium saltpeter and two doses of potassium (0.3, 0.6 and 0.9 g dm -3) in the form of chloride and sulfate. The increased amounts of nitrogen and potassium generally contrib-uted to the increase of fresh leaf weight yield. Plants nourished with KCl had larger con-centrations of L-ascorbic acid, chlorine and calcium, whereas the contents of protein, su-gars in total, as well as sulfates were smaller, as compared to plants nourished with K 2 SO 4 .

Full text

Acta Sci. Pol., Hortorum Cultus 8(4) 2009, 23-33
GROWTH AND YIELD OF GARDEN ROCKET
(Eruca sativa. Mill.) AFFECTED BY NITROGEN
AND POTASSIUM FERTILIZATION
Renata Nurzyńska-Wierdak
University of Life Sciences in Lublin
Abstract. We studied the effect of differentiated nitrogen-potassium fertilization upon the
growth, yield and chemical composition of garden rocket leaves grown in unheated
greenhouse in autumn. Two nitrogen doses were applied (0.3 and 0.6 g dm
-3
) in the form
of calcium saltpeter and two doses of potassium (0.3, 0.6 and 0.9 g dm
-3
) in the form of
chloride and sulfate. The increased amounts of nitrogen and potassium generally contrib-
uted to the increase of fresh leaf weight yield. Plants nourished with KCl had larger con-
centrations of L-ascorbic acid, chlorine and calcium, whereas the contents of protein, su-
gars in total, as well as sulfates were smaller, as compared to plants nourished with
K
2
SO
4
.
Key words: garden rocket, fertilization, yield of fresh weight, chemical composition of
leaves
INTRODUCTION
Garden rocket (Eruca sativa Mill.) is grown in Europe mainly under shields, to ob-
tain fresh, aromatic leaves. The rocket producers are mainly focused on information
concerning the manner of plant nutrition and yield quantity and quality, strictly related
to it. Nitrogen and potassium, as basic plant nutrients, are also indispensable elements in
human nutrition. Both nitrogen and potassium are taken by plants in large amounts, as
compared with other nutrients. These elements are necessary for all plants to produce
yield and form its qualitative features that are advantageous for consumption and proc-
essing. Some vegetables, especially those with short vegetation period, have a natural
ability to accumulate proportionally significant amounts of nitrates. We refer to exces-
sive accumulation of these compounds when their uptake is greater than the possibility
of their reduction. This occurs, among others, when there is light deficiency, or small
precipitation intensity [Paschold 1989, Sady et al. 1995]. Main nitrate accumulation
Corresponding author – Adres do korespondencji: Renata Nurzyńska-Wierdak University of Life
Sciences in Lublin, Departament of Vegetables and Medicinal Plants, Leszczyńskiego 58, 20-068
Lublin, e-mail: renata.nurzynska@up.lublin.pl

24 R. Nurzyńska-Wierdak
_____________________________________________________________________________________________________________________________________________
Acta Sci. Pol.
factors, besides small light intensity, include the applied dose of fertilizer nitrogen
[Chen et al. 2004, Santamaria et al. 1997]. The application of large doses of nitrogen
fertilization not always leads to the increase of crop plant yields, and most often it en-
hances the accumulation of nitrates in their edible parts. Ceylan and others [2002] ob-
tained the greatest rocket leaf yield, applying N at the dose of 300 kg ha
-1
, at the same
time the largest amounts of III and V nitrates were found in the leaves of examined
plants at the dose of 500 kg ha
-1
.
The uptake of nitrogen by plants in the form of anion NO
3
-
and cation NH
4
+
is re-
lated to the mutual influence of other nutrients upon the inorganic nitrogen connections.
One of the basic conditions for good use of soil nitrogen is good soil abundance in
phosphorus and potassium. Hanafy et al. [2000] demonstrated that applying double dose
of phosphorus and potassium contributed to the decrease of nitrate concentrations, even
at a large nitrogen dose. Similarly, other authors [Ali et al. 1985, Wu and Wang 1995,
Zong et al. 1997] proved that the increase of potassium fertilization affects the decrease
of nitrate accumulation in the yield of certain vegetables. In the glasshouse cultivation
of vegetables the kind of potassium salt, used as a fertilizer, is of crucial importance.
Borowski et al. [2000] found that the intensity of net photosynthesis at fertilizing to-
mato plants with K
2
SO
4
was greater as compared to KCl. Besides, other authors
[Nurzyński 1976, 1986a, 1986b, 2005; Nurzyński and Michałojć 1998; Nurzyński et al.
1980, 1982a, 1982b] demonstrated that applying KCl and K
2
SO
4
did not significantly
affect the yields of tomato, cucumber, lettuce and other plants, but it substantially dif-
ferentiated the contents of particular nutrients in the growing mediums and leaves, de-
spite the fact that fertilization with N, P, K, Ca and Mg remained on the same level.
Only anions connected with potassium were different. The authors of works listed
above emphasize that the leaves of plants nourished with K
2
SO
4
contained more nitrates
and less Ca, Mg, Mn and Mo, as compared to KCl fertilization, which results from an-
tagonistic effect of sulfates upon the uptake of molybdenum.
The objective of the study presented in this paper was to define the effect of differ-
entiated nitrogen-potassium fertilization upon the growth of rocket, amount of fresh leaf
weight yield and the chemical composition of plants in autumn glasshouse cultivation.
MATERIAL AND METHODS
The studies were conducted in the years 2004–2005 in an unheated detached glass-
house belonging to the Experiment Farm of the University of Life Sciences in Lublin,
located in northern-southern direction in autumn period. The plants were grown in pots
of the capacity of 2 dm
3
, filled with peat limed with fertilizer chalk in the amount of
4.0 g dm
3
peat to pH 6.2, mixed with clayey-sandy soil (surface soil – arable layer) in
the volume proportion of 9:1. We applied fertilization expressed in g dm
-3
of the sub-
stratum: N – 0.3, 0.6 and 0.9 in the form of calcium saltpeter: K – 0.3 and 0.6 in the
form of KCl and K
2
SO
4
, P – 0.4 g dm
-3
as superphosphate 20% P, Mg – 0.2 g dm
-3
as
magnesium sulfate and microelements: 8.0 Fe, 5.1 Mn, 13.3 Cu, 0.74 Zn, 1.6 B, 3.7 Mo.
Rocket seeds from the Italian seed manufacturer Landen were sown at the beginning of
September, leaving 3 plants in each pot. Each series comprised 8 repetitions (24 plants).

Growth and yield of garden rocket (Eruca sativa. Mill.) affected by nitrogen... 25
_____________________________________________________________________________________________________________________________________________
Hortorum Cultus 8(4) 2009
The plants were watered as the need arose, 1–2 times a day, with the same amount of
water. Harvesting was conducted after 55–60 days of vegetation, shearing whole leaf
rosettes. We defined the fresh yield weight, number of leaves in a rosette and the plant
height. Immediately after harvest we determined the contents of dry matter, total sugars
and monosaccharides in the above-ground parts of the plants (by means of the Luff-
-Schoorl method), as well as the contents of L-ascorbic acid (using Tillmans’s method).
Having dried the plant material in the temperature of 70°C and having minced it we
determined N-total contents (by means of Kjeldahl’s method, on the automatic Kjel-
-Foss apparatus), we also determined the contents of N-NH
4
and N-NO
3
(using Bremn-
ers distillation method, modified by Starck), and we also colorimetrically determined
chlorine with AgNO
3
, as well as sulfates with BaCl
3
. After dry-burning in the tempera-
ture of 550°C the following were determined: phosphorus – colorimetrically with am-
monium vanadomolybdate, calcium and potassium by means of atomic absorption
method. After harvest, we determined 0.03 M CH
3
COOH: N-NH
4
and N-NO
3
, phos-
phorus, potassium, calcium and magnesium in the growing medium extract, using the
same methods as in the plant material. We determined the growing medium reaction pH
potentiometrically in H
2
O, salt concentration in the growing medium (EC) – conducto-
metrically. We worked out the results statistically, using the method of variance analysis
for double cross classification, assessing the significance of differences by means of
Tukey confidence intervals and making LSD calculations at the significance level of
α = 0.05.
RESULTS
The applied nitrogen doses significantly affected the quantity and quality of rocket
yield (tab. 1). The plants fed with a larger nitrogen dose had significantly bigger fresh
weight yield (20.1 g per pot) than plants fed with smaller doses of this nutrient (17.5 g
per pot). However, the mean height of rocket plants was significantly bigger when
a smaller dose of nitrogen was applied, than in the case of feeding plants with a smaller
dose of this component. No significant changes were found in the mean number of
rocket leaves, depending on the amount of the applied nitrogen. We demonstrated
a significant effect of nitrogen dose upon the contents of protein, L-ascorbic acid, total
sugars and monosaccharides in the examined plants (tab. 1). The plants fed with a larger
dose of nitrogen accumulated significantly more protein and less L-ascorbic acid, total
sugars and monosaccharides, as compared to the remaining ones.
It was demonstrated that there was no significant effect of the kind of applied potas-
sium fertilizer upon the yield quantity, mean height and number of examined plants, as
well as upon the contents of dry matter, protein, L-ascorbic acid and sugars (tab. 1). The
differentiated potassium doses (the means from objects of both potassium fertilizers),
however, significantly affected the quantity of rocket yield. The highest yield (19.5 g
per pot) was obtained with the application of mean K dose, and the differences between
the yields of plants fed with the second and third dose of potassium were statistically
insignificant. No significant affect of potassium dose was found upon the mean height
and number of rocket leaves, as well as upon the contents of protein and monosaccha-

Table 1. The effect of nitrogen and potassium fertlization on the yield of garden rocket in autumn cultivation (mean from 2004–2005)
Tabela 1 Wpływ nawożenia azotowo-potasowego na plon rokietty siewnej w uprawie jesiennej (średnio z 2004–2005)
In fresh weight
W świeżej masie
Fertilization
Nawożenie
Kind of fertilizer
Rodzaj nawozu
dose
dawka
g N
dm
-3
dose
dawka
g K dm
-3
Yield of
fresh weight
(g pot
-1
)
Plon świeżej
masy
(g wazon
-1
)
Plant height
Wysokość
rośliny
(cm)
Number
of leaves
(per plant)
Liczba
liści
(z rośliny)
Dry matter
Sucha
masa
(%)
Protein
Białko
(%s.m.)
L-ascorbic acid
Kwas
L-askorbinowy
(mg 100g
-1
)
Total sugars
Cukry ogółem
(%)
Monosaccharides
Cukry redukujące
(%)
0.3
0.3
0.6
0.9
18.4
21.0
15.6
14.5
15.2
18.0
7.3
8.4
8.6
9.7
10.0
10.2
34.9
34.9
34.8
243.2
198.8
169.9
1.07
1.26
1.09
0.38
0.37
0.43
KCl
0.6
0.3
0.6
0.9
19.0
19.9
19.2
16.6
15.0
14.9
8.7
7.6
8.4
9.6
8.2
11.0
36.1
35.8
35.3
201.7
167.0
135.7
1.27
0.93
1.03
0.25
0.21
0.33
Mean – Średnio 18.9 a 15.7 a 8.2 a 9.8 a 35.3 a 185.2 a 1.11 b 0.33 a
0.3
0.3
0.6
0.9
16.9
15.3
17.8
18.5
16.6
17.9
9.9
8.9
8.3
9.1
9.5
10.2
35.4
35.3
35.4
188.6
178.0
150.9
1.68
1.21
1.53
0.41
0.46
0.30
K
2
SO
4
0.6
0.3
0.6
0.9
18.7
21.8
21.8
15.4
16.5
14.6
8.7
8.6
8.7
9.8
10.8
10.2
36.9
36.1
37.2
169.5
178.7
167.0
0.98
1.05
0.95
0.37
0.25
0.28
Mean –Średnio 18.8 a 16.7 a 8.9 a 9.9 a 36.1 a 172.1 b 1.23 a 0.35 a
Mean for N dose
Średnio dla dawki N
0.3
0.6
17.5 b
21.1 a
16.9 a
15.5 b
8.6 a
8.5 a
9.8 a
9.9 a
35.2 a
36.3 a
187.4 a
169.9 b
1.31 a
1.04 b
0.39 a
0.28 b
Mean for K dose
Średnio dla dawki K
0.3
0.6
0.9
18.3 b
19.5 a
18.6 ab
16.3 a
15.8 a
16.4 a
8.7 a
8.4 a
8.5 a
9.6 b
9.6 b
10.4 a
35.8 a
35.5 a
35.7 a
200.8 a
179.4 b
155.9 c
1.25 a
1.11 b
1.15 b
0.35 a
0.32 a
0.34 a
Means followed by the same letter are not significantly different at α = 0.05
Średnie oznaczone tą samą literą nie różnią się pomiędzy sobą istotnie przy α = 0,05

Table 2. The effect of nitrogen and potassium fertlization on the chemical composition of rocket leaves (mean from 2004–2005)
Tabela 2. Wpływ nawożenia azotowo-potasowego na skład chemiczny liści rokietty (średnio z 2004–2005)
Fertilization – Nawożenie % of dry matter – % suchej masy
Kind of fertilizer
Rodzaj nawozu
Dose
Dawka
g N dm
-3
Dose
Dawka
g K dm
-3
N-total
N-og
N-NO
3
S-SO
4
Cl P K Ca Mg
0,3
0,3
0,6
0,9
5.59
5.59
5.57
0.97
1.11
1.06
0.68
0.70
0.68
1.13
1.39
1.61
0.57
0.56
0.57
5.30
6.26
5.73
3.19
3.79
2.85
0.36
0.44
0.33
KCl
0,6
0,3
0,6
0,9
5.77
5.72
5.64
0.99
1.01
0.98
0.62
0.66
0.61
1.40
1.38
1.39
0.52
0.51
0.56
5.63
5.48
6.67
3.50
3.10
3.63
0.34
0.36
0.39
Mean – Średnio 5.65 a 1.02 a 0.66 b 1.39 a 0.55 a 5.85 a 3.35 a 0.37 a
0,3
0,3
0,6
0,9
5.67
5.65
5.66
1.20
1.03
0.98
0.79
0.67
0.67
0.82
0.81
0.82
0.61
0.59
0.52
5.57
6.76
6.07
2.98
3.31
2.93
0.35
0.32
0.28
K
2
SO
4
0,6
0,3
0,6
0,9
5.90
5.78
5.95
1.06
1.00
0.98
0.70
0.78
0.77
0.78
1.00
0.93
0.56
0.52
0.57
6.26
5.68
6.06
3.83
2.99
3.26
0.43
0.39
0.36
Mean – Średnio 5.77 a 1.04 a 0.73 a 0.86 b 0.58 a 6.07 a 3.22 a 0.36 a
Mean for N dose
Średnio dla dawki N
0,3
0,6
5.62 b
5.80 b
1.06 a
1.00 a
0.70 a
0.69 a
1.10 a
1.15 a
0.57 a
0.56 a
5.95 a
5.97 a
3.18 b
3.39 a
0.35 a
0.38 a
Mean for K dose
Średnio dla dawki K
0,3
0,6
0,9
5.73 a
5.69 a
5.71 a
1.06 a
1.04 a
1.00a
0.70 a
0.70 a
0.68 a
1.03 b
1.15 a
1.19 a
0.57 a
0.55 a
0.56 a
5.69 b
6.05 a
6.13 a
3.38 a
3.30 a
3.17 b
0.37 a
0.38 a
0.34 a
Means followed by the same letter are not significantly different at α = 0.05
Średnie oznaczone tą samą literą nie różnią się pomiędzy sobą istotnie przy α = 0,05

Table 3. The nutrients content (mg dm
-3
), pH
H2O
and EC (mS cm
-1
) of the growing medium (mean from 2004–2005)
Tabela 3. Zawartość składników pokarmowych w podłożu (mg dm
-3
), pH
H2O
i EC (mS cm
-1
) (średnio z 2004–2005)
Kind of fertilizer
Rodzaj nawozu
Dose
Dawka
g N dm
-3
Dose
Dawka
g K dm
-3
N-NH
4
N-NO
3
N-NH
4
+
N-NO
3
S-SO
4
Cl P K Ca Mg pH EC
0.3
0.3
0.6
0.9
11
22
26
240
207
232
251
229
258
180
200
190
260
420
720
240
210
210
103
356
709
1599
1453
1278
222
208
204
5.67
5.73
5.81
1.81
1.77
2.37
KCl
0.6
0.3
0.6
0.9
21
22
15
297
350
357
318
372
362
202
200
195
220
500
800
245
245
225
146
355
543
1575
1649
1666
184
168
177
5.67
5.53
5.58
2.30
2.18
2.41
Mean – Średnio 15 b 281 b 296 b 195 b 487 a 229 a 552 a 1537 b 194 b 2.14 a
0.3
0.3
0.6
0.9
15
28
18
182
218
261
197
246
279
205
232
330
65
45
50
220
240
225
115
398
694
1897
1959
2452
209
294
366
5.84
5.83
5.92
1.49
2.08
2.49
K
2
SO
4
0.6
0.3
0.6
0.9
20
21
22
398
406
379
419
427
402
265
265
312
60
65
55
225
225
220
101
391
584
2215
1620
2492
264
250
277
5.71
5.69
5.68
2.11
2.28
2.76
Mean – Średnio 21 a 307 a 328 a 268 a 53 b 226 a 547 a 2106 a 277 a 2.20 a
Mean for N dose
Średnio dla dawki N
0.3
0.6
18 a
19 a
223 b
365 a
241 b
383 a
223 a
240 a
260 b
283 a
224 a
231 a
579 a
520 b
1773 b
1890 a
250 a
220 b
2.00 b
2.34 a
Mean for K dose
Średnio dla dawki K
0.3
0.6
0.9
17 b
23 a
20 ab
279 b
295 ab
307 a
296 b
319 ab
325 a
213 b
224 b
257 a
151 c
258 b
406 a
233 a
230 a
220 a
241 c
575 b
832 a
1822 b
1670 c
1972 a
220 b
230 b
256 a
1.93 b
2.08 b
2.51 a
Means followed by the same letter are not significantly different at α = 0.05
Średnie oznaczone tą samą literą nie różnią się pomiędzy sobą istotnie przy α = 0,05

Growth and yield of garden rocket (Eruca sativa. Mill.) affected by nitrogen... 29
_____________________________________________________________________________________________________________________________________________
Hortorum Cultus 8(4) 2009
rides. Significantly the greatest dry matter contents (10.4%) were found in plants fed
with the largest potassium doses, as compared to other plants. The concentrations of
protein and monosacchaides, in turn, was the greatest in plants fed with the smallest
dose of potassium. Increasing the applied potassium dose caused significant decrease of
the amount of L-ascorbic acid. Rocket fed with the smallest potassium dose had signifi-
cantly the largest content of this nutrient (200.8 mg 100 g
-1
fresh weight) and the largest
total concentration of sugars (1.25% fresh weight), with reference to the remaining ones.
We found a significant influence of the kind of applied potassium fertilizer upon the
concentration of mineral components (tab. 2). Rocket fed with potassium sulfate con-
tained significantly more nitrogen in total, sulfates and potassium than plants fed with
KCl, which revealed significantly the largest contents of chlorine and calcium. The
concentrations of N-NO
3
, P and Mg did not significantly depend upon the applied form
of potassium. No significant effect of potassium dose was found upon the total content
of nitrogen in rocket leaves. However, the differentiation of potassium doses signifi-
cantly affected the contents of nitrates, chlorine, potassium, calcium and magnesium. As
the potassium doses increased, the concentrations of N-NO
3
decreased (only in objects
with K
2
SO
4
), and the concentrations of Ca and Mg decreased as well. Significantly the
largest amounts of potassium were found in plants fed with the largest doses of K. We
demonstrated lack of significant influence of potassium dose upon the contents of sul-
fates (also when K
2
SO
4
was applied), and phosphorus The concentration of sulfates was
the smallest when the largest dose of K was applied, whereas the concentration of phos-
phorus was the smallest with the average K dose. The increasing doses of KCl signifi-
cantly influenced the increase of chlorine contents in rocket leaves. No significant dif-
ferences were found between mean concentration of this component in plants fed with
average and the largest potassium dose.
The applied potassium doses differentiated the contents of mineral components in
the examined plants to a small extent (tab. 2). Significantly larger contents of total ni-
trogen, calcium and magnesium were found in plants fed with a larger dose of nitrogen
than the plants getting less of that component. No significant effect of applied nitrogen
upon the contents of nitrates was found.
We revealed a significant effect of differentiated nitrogen-potassium fertilization
upon the chemical composition of growing medium after plant harvesting (tab. 3). In the
objects with K
2
SO
4
we found significantly larger concentrations of ammonium, nitrate
and mineral nitrogen concentrations, as well as significantly larger concentrations of
calcium and ammonium sulfates, as compared to KCl. The contents of chlorine in the
growing medium was very differentiated and it depended on the kind and dose of ap-
plied potassium fertilizer as well as on the nitrogen dose. At the application of larger
nitrogen dose we also found in the growing medium significantly more nitrate and min-
eral nitrogen, chlorine, potassium, calcium and magnesium. No significant effect of the
kind of applied potassium fertilizer was demonstrated upon the reactions and concentra-
tions of nutrients in examined growing media after plant harvesting (tab. 3). The grow-
ing medium fertilized with K
2
SO
4
had larger pH and EC values, as compared to KCl.
The increased dose of the applied nitrogen affected the decrease of pH value and in-
crease of ion concentration (EC). The increased potassium dose, in turn, did not differ-
entiate the pH values, only causing the increase of EC values.

30 R. Nurzyńska-Wierdak
_____________________________________________________________________________________________________________________________________________
Acta Sci. Pol.
DISCUSSION
The yield of fresh rocket weight significantly depended upon the dose of applied ni-
trogen and potassium. The increase of nitrogen dose caused a significant increase of
yield, which was also demonstrated in the previous paper [Nurzyńska-Wierdak 2001].
The increased amount of applied potassium caused the increased yield of examined
plants, but only at 0.6 g dm
-3
. Further increasing of potassium doses diminished the
yield of fresh rocket weight. This dependence is confirmed by results of the studies
conducted in the spring period [Nurzyńska-Wierdak 2006b]. Similarly, El-Bassiony
[2006] demonstrated the increase of fresh leaf weight and total yield of onion under the
influence of increased potassium dose. The application of potassium in the form of KCl
and K
2
SO
4
did not differentiate the quantity of rocket yield and the contents of dry mat-
ter, protein, total sugars and monosaccharides. This is confirmed by Nurzyński’s con-
clusion [2005], that potassium is equally well taken up by plants from those fertilizers.
Potassium plays an important role in the formation of protein compounds in plants.
Its presence intensifies the process of nitrate reduction. The examined rocket plants
accumulated less nitrates in their leaves under the influence of increased potassium
dose, however the differences were not statistically significant. Hanafy et al. [2000]
report that the application of double potassium and phosphorus doses in rocket cultiva-
tion contributed to the decrease of nitrate concentrations even at a large dose of nitro-
gen. Similarly, other authors [Ali et al. 1985, Wu and Wang 1995, Zong et al. 1997]
claim that the increase of potassium fertilization affects the decrease of nitrate accumu-
lation in the yields of certain vegetables.
The concentration of N-NO
3
in the leaves of the examined rocket plants did not sig-
nificantly depend on the kind of applied potassium fertilizer, although less of these
compounds were found in plants nourished with KCl. Nurzyński [2005] reports that
plants fed with potassium chloride accumulate less nitrates and more molybdenum, as
compared to potassium sulfate. Nitrate and chloride anions, as univalent, balance out, so
the more chlorides there are, the less nitrates. Substantial accumulation of sulfates in the
growing medium causes increased concentration of nitrates in plants, which results from
their impaired ability of reduction and further processing. The presented paper demon-
strates that as a result of nourishing plants with K
2
SO
4
, after harvesting there remained
significantly more N-NH
4
, N-NO
3
, N-NH
4
+ N-NO
3
, S-SO
4
, Ca and Mg in the growing
medium, and significantly less chlorine, as compared to KCl. Simultaneously, the appli-
cation of potassium in the form of KCl and K
2
SO
4
did not significantly affect the con-
tents of macrocomponents and nitrates in plant leaves, except the obvious differences in
the contents of sulfates and chlorine. This can probably be justified by appropriate con-
centration of nutrients in the growing medium (EC), slightly larger in the objects with
K
2
SO
4
, allowing for correct uptake of water, as well as micro- and macroelements by
plants. When analyzing the chemical composition of growing medium after plant har-
vesting, one can notice that the EC values were affected to the greatest extent by potas-
sium and nitrate ions. Similar dependences were demonstrated by Golcz et al. [2008].
As Nurzyński [2005] reports, high chloride concentration in the growing medium does
not cause a significant increase of EC values. This is confirmed by results of the pre-
sented studies, where at chloride mean contents in growing medium of 487 g dm
-3
the

Growth and yield of garden rocket (Eruca sativa. Mill.) affected by nitrogen... 31
_____________________________________________________________________________________________________________________________________________
Hortorum Cultus 8(4) 2009
EC value was 2.14 and did not significantly differ from the EC value of the growing
medium, containing chloride merely 53 g dm
-3
(objects with K
2
SO
4
).
The nutritional value of examined rocket plants, related to the participation of dry
matter and concentrations of monosaccharides, total sugars, protein, L-ascorbic acid and
mineral components, significantly depended upon the applied fertilization. Together
with the increase of nitrogen dose, the contents of dry matter, protein, N-total, Cl, K, Ca
and Mg, though the differences were not always statistically significant. The concentra-
tions of L-ascorbic acid, monosaccharides and total sugars, however, were significantly
smaller as an effect of the increased nitrogen dose, which confirms the results of previ-
ous studies [Nurzyńska-Wierdak 2001, 2006a, b], the results obtained by Vyas et al.
[1995], as well as by Golcz and Kozik [2004]. The increased potassium fertilization,
applied in the presented studies, caused a significant decrease of L-ascorbic acid in
rocket leaves, which confirms the results of previous studies concerning rocket growing
in spring [Nurzyńska-Wierdak 2006b]. However, different results were obtained by
Golcz and Kozik [2004]. These authors demonstrated that together with the increase of
potassium dose the vitamin C contents increases in pepper fruit. This can be explained
by differences in the course of physiological processes in the examined vegetative and
generative plant organs. Total sugars concentration in the examined rocket leaves sig-
nificantly depended on the applied potassium dose and it was the largest at the smallest
dose. Similarly, Venkatesan et al. [2005], studying the effect of various potassium
sources and doses upon the quality of potassium leaves, demonstrated that the smallest
potassium dose, applied in the form of K
2
SO
4
was sufficient for increasing biochemical
parameters. Lin et al. [2004] in turn, demonstrated a significant effect of potassium dose
upon the quality of melon fruit. These authors report that with the potassium application
of 240 mg dm
-3
growing medium the greatest concentrations of total sugars and vitamin
C were obtained, which improved the taste and smell of the examined fruit.
CONCLUSIONS
1. Fresh leaf weight yield of the rocket grown in autumn significantly depended
upon the applied nitrogen and potassium doses.
2. The potassium applied in the forms of KCl and K
2
SO
4
was equally well taken in
by rocket plants. No significant difference in fresh leaf weight yield of the rocket fed
with KCl and K
2
SO
4
was found.
3. The contents of L-ascorbic acid, total sugars and monosaccharides decreased as
an effect of increased nitrogen and potassium doses. In the objects with KCl a signifi-
cantly larger L-ascorbic acid concentration was found in rocket leaves, as compared to
K
2
SO
4
.
4. The applied fertilization did not significantly differentiate the nitrate contents in
the leaves of examined plants.
5. Increased chloride concentration in the growing medium after the application of
KCl did not cause a significant increase of EC values, as compared with K
2
SO
4
.

32 R. Nurzyńska-Wierdak
_____________________________________________________________________________________________________________________________________________
Acta Sci. Pol.
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WZROST I PLON ROKIETTY SIEWNEJ (Eruca sativa Mill.) POD
WPŁYWEM NAWOŻENIA AZOTOWO-POTASOWEGO
Streszczenie. Badano wpływ zróżnicowanego nawożenia azotowo-potasowego na wzrost,
plon i skład chemiczny liści rokietty siewnej uprawianej w szklarni nieogrzewanej
w okresie jesiennym. Zastosowano dwie dawki azotu (0,3 i 0,6 g dm
-3
) w formie saletry
wapniowej oraz trzy dawki potasu (0,3; 0,6 i 0,9 g dm
-3
) w postaci chlorku potasu i siar-
czanu potasu. Zwiększanie ilości azotu i potasu przyczyniało się na ogół do zwiększania
plonu świeżej masy liści. Rośliny żywione KCl charakteryzowały się większą koncentra-
cją kwasu L-askorbinowego, chloru i wapnia, natomiast mniejszą zawartością białka, cu-
krów ogółem i siarczanów w porównaniu z roślinami żywionymi K
2
SO
4
.
Słowa kluczowe: rokietta siewna, nawożenie, plon świeżej masy liści, skład chemiczny
liści
Accepted for print – Zaakceptowano do druku: 17.12.2009