Špičák, Czech Republic, 2010
IX. Alps-Adria Scientific Workshop
EFFECT OF FOLIAR FERTILIZERS ON CHLOROPHYLL
CONTENT INDEX AND YIELD OF POTATO CROP GROWN
UNDER WATER STRESS CONDITIONS
1
Tea HORVAT – Milan POLJAK
1
Tomislav KARAŽIJA
1
2
1
1
– Boris LAZAREVIĆ – Zlatko SVEČNJAK
2
–
Department of Plant Nutrition, Faculty of Agriculture, University of Zagreb, Svetošimunska 25, HR-10000
Zagreb, Croatia, e-mail: [email protected]
Department of Field Crop Production, Grassland and Forages, Faculty of Agriculture, University of Zagreb
Abstract: The aim of this study was to determine the effect of three foliar fertilizers (Epso Salt, Megagreen
and Drin) and control treatment (with no foliar fertilizer) on the chlorophyll content index, tuber size and yield
of potato crop grown under water stress conditions. The experiment was conducted during three growing
seasons (2005, 2006 and 2007) in the greenhouse using variety 'Courage' and arranged in a split-plot design
with three replications. Foliar fertilization was carried out five times during vegetation in the period from the
start of tuber formation to the stage of full tuberization. Water stress was induced at the full tuberization
growth stage. There was no significant difference in chlorophyll content index in potato leaf influenced by
foliar fertilizers between water stress conditions and optimum water supply. However, tuber yield was
significantly reduced by an average of 15 % under water stress conditions. In addition, water stress resulted in
a significantly higher number of 0-25 mm size tubers, but lower number of 50-75 mm size tubers. Foliar
application of Epso Salt brought about similar tuber yields under conditions of water stress and optimum
water supply. In contrast, Megagreen, Drin and control treatment achieved significantly higher tuber yield
under optimum water supply when compared to water stress conditions.
Keywords: potato, foliar fertilizers, water stress, chlorophyll content index, tuber yield
Introduction
Water stress is an important factor which induces significant alterations in plant
physiology and biochemistry (El-Tayeb, 2006). It causes inhibition of growth which is
reflected in a restriction of chlorophyll content and photosynthesis, dry matter formation
and yield (Poljak et al., 2005; Hnilička et al., 2007). The potato (Solanum tuberosum L.)
is well known as one of the most sensitive crops to water stress. Water stress during mid
and late bulking periods reduces yield while increases the percentage of undersized
tubers and causes tubers brown spots (Horvat et al., 2008). Soil fertilization is not
always sufficient to meet the needs of crops, especially in water stress conditions,
because the root is not able to absorb nutrients in adequate quantities from the upper
layer of dry soil. Furthemore, in water stress conditions transport of certain nutrients
(Ca, Mg, B, Mn) that are transported through the plant by xylem is limited. Apart from
soil fertilization, fertilizers can be applied foliar through leaves and stems. On the
market there are different foliar fertilizers, which are often mixtures of micronutrients
and secondary nutrients. Their application is recommended to increase the yield and
quality of crops. However, there are very few scientific results based on their
effectiveness on the plants metabolism.
The objective of this study was to determine the effect of foliar fertilizers on the
chlorophyll content index, tuber size and yield of potato crop grown under water stress
conditions.
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DOI: 10.1556/Novenyterm.59.2010.Suppl.1
Vol. 59, 2010, Suppl.
Növénytermelés
Materials and methods
The experiment was conducted during three growing seasons (2005, 2006 and 2007) in
the greenhouse of the Faculty of Agriculture, University of Zagreb in partly controlled
conditions. Potato tubers of variety 'Courage' were planted in 25 L pots filled with a
mixture of soil and perlite at a ratio of 3:1. The basic fertilization, calculated per pot,
was carried out with 700 kg ha-1 NPK 7:20:30 and 250 kg ha-1 KAN at pre-planting.
The experiment consisted of three foliar fertilizers (Epso Salt (Mg, S, B, Mn), Drin
(alpha amino acid), Megagreen (Ca) and control treatment (with no foliar fertilizer) and
was arranged in a randomized split-plot design with three replications. Foliar
fertilization was carried out five times during vegetation (50, 60, 70, 80 and 90 days
after planting) in the period from the start of tuber formation to the stage of full
tuberization. Foliar fertilizers were applied as instructed by manufacturers (Epso Salt at
a dose of 25 kg ha-1, Drin 0,5 l ha-1 and Megagreen at a dose of 2 kg ha-1) with the water
consumption of 300 l ha-1 calculated per pot. Drip irrigation was used. Water deficit
stress was induced at the full tuberization growth stage (90 days after planting) by
interrupting the irrigation. Chlorophyll content index in potato leaves was measured by
portable CCM 200 apparatus (ADC, Bio Scientific Ltd. UK) on the second and sixth
day after exposure of plants to water stress. After 20-day exposure of plants to water
stress, fresh tuber yield and the number of tubers by size were calculated. Data were
analyzed with analysis of variance. Mean separation was obtained using a protected
LSD test at the 0,05 probability level when significant F-tests (P ≤ 0.05) were observed.
Results and discussion
Chlorophyll content index significantly differed depending on the water stress
conditions and optimum water supply conditions in individual growing seasons (Figure
1). In 2005 and 2006, a significant difference in chlorophyll content index in water
stress and optimum water supply conditions was not found. In contrast, chlorophyll
content index in water stress conditions in 2007 was 18,7 and was significantly lower by
40 % compared to optimum water supply conditions (31,0). Reduction of chlorophyll
content in water stress conditions was reported by Kiani et al. (2008). There was no
significant difference in chlorophyll content index in potato leaf influenced by foliar
fertilizers between water stress conditions and optimum water supply in both growing
seasons.
The analysis of variance showed that water stress significantly influenced the potato
tuber yield and number of 0-25 mm and 50-75 mm size tubers (Table 1). Potato tuber
yield was significantly reduced in water stress conditions by an average of 15 % and
amounted 370,0 g per plant compared with 433,5 g per plant under optimum water
supply conditions. The negative impact of water stress during and at the end of tuber
bulking on potato yield and quality was also found by Pereira and Shock (2006). The
authors reported the reduction in yield and specific gravity and increase in reducing
sugar in potato tuber due to water stress.
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Špičák, Czech Republic, 2010
IX. Alps-Adria Scientific Workshop
Non stress
50,0
40,0
31,0
18,7
28,4
10,0
29,1
20,0
34,1
30,0
32,9
Chlorophyll content index
Stress
0,0
2005
2006
2007
Growing season
Figure 1. The average chlorophyll content index in stress and non stress conditions in growing seasons 2005,
2006 and 2007. LSD 0,05 =5,9; bars apply for comparing stress and non stress conditions within the same
growing season.
Foliar treatments significantly differed in tuber yield produced under water stress and
optimum water supply conditions (Table 1).
Table 1. Combined analysis of variance for potato yield and number of tubers by size.
Potato yield
Number of tubers by size
Source of variation
(g per plant)
0-25mm
25-50mm
50-75mm
Growing season (GS)
*
**
NS
*
Treatment (T)
*
NS
NS
*
GS × T
NS
NS
NS
NS
Stress (S)
**
*
NS
*
GS × S
*
NS
NS
NS
T×S
*
NS
NS
NS
NS Not significant; * Significant at P ≤ 0.05; ** Significant at P ≤ 0.01
Foliar application of Epso Salt brought about similar tuber yields under conditions of
water stress and optimum water supply (Figure 2). In contrast, plants subjected to
control, Megagreen and Drin had a significantly higher tuber yield under optimum
water supply when compared to water stress conditions. Takacs-Hajos et al. (2007)
indicated a positive impact of foliar fertilizer Epso Salt on the yield and quality of sugar
beet. In water stress conditions Megagreen treatment achieved a higher yield (418,3 g
per plant). The smallest yield in stress conditions was obtained under the influence of
Drin treatment.
In water stress conditions, a significantly higher number of 0-25 mm size tubers, but
lower number of 50-75 mm size tubers was determined. The likely reason is that in
water deficit conditions the stoma closure decreased the intensity of photosynthesis,
prevented the translocation of assimilates into the tuber and further thickening. A
reduced number of larger tubers in water stress conditions was reported by Walworth
and Carling (2002). The absence of interaction between treatments and stress indicate
that treatments responded similarly in the number of tubers by size in water stress and
optimum water supply conditions (Table 1).
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DOI: 10.1556/Novenyterm.59.2010.Suppl.1
Vol. 59, 2010, Suppl.
Növénytermelés
Non-w ater stress
500,0
450,0
459,2
418,3
421,6
315,5
250,0
386,0
300,0
353,4
350,0
455,1
400,0
392,7
Potato yield (g per plant)
Water stress
200,0
Control
Epso Salt
Drin
Megagreen
Treatments
Figure 2. The average yield of potato tubers following application of foliar treatments compared with control
in stress and non stress conditions. LSD 0,05 = 33,53 g per plant; bars apply for comparing treatment in stress
and non stress conditions.
Conclusions
A significantly lower average tuber yield was attained in water stress conditions. In
addition, water stress resulted in a significantly higher number of 0-25 mm size tubers,
but lower number of 50-75 mm size tubers. Our findings have shown a positive impact
of foliar fertilizer Epso Salt on potato tuber yield in water stress conditions. There was
no significant difference in chlorophyll content index in potato leaf influenced by foliar
fertilizers between water stress conditions and optimum water supply.
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