POTASSIUM RATE AND ACCOMPANYING ANIONS IMPACT
ON POTASSIUM, CALCIUM AND MAGNESIUM UPTAKE BY
STRAWBERRIES IN SOILLESS CULTURE
1
1
2
Miroslav LISJAK – Aleksandar STANISAVLJEVIĆ – Marija ŠPOLJAREVIĆ – Boris
1
ĐURĐEVIĆ
1
2
Department of agroecology, Faculty of agriculture, University of J.J. Strossmayer, Trg Sv. Trojstva 3,
31 000 Osijek, Croatia, e-mail: mlisjak@pfos.hr
Department of biology, University of J.J. Strossmayer, Trg Lj. Gaja 6, 31 000 Osijek, Croatia
Abstract: This paper refers to the influence of K fertilization on K, Ca and Mg relations in strawberry cv.
Elsanta grown in peat mix, in a plastic greenhouse with vertical pot system. Four fertilization variants (control
- 0.72 g K plant-1 as KNO3 and three variants with 2.22 g K plant-1 as the combinations of KNO3 and K2SO4,
KCl or KHCO3) were applied using trickle irrigation in fruit bearing stage in autumn. The amount of K
leached through the verticals containing eight pots and four plants per pot was influenced mostly by K rate.
The highest yield was obtained on control variant with lower K dose applied as nitrate. The enhanced K rate
influenced on leaf K concentration, showing significant differences among the applied combinations of K salts
and the antagonism with Mg uptake was observed. The possible role of accompanying anions in the nutrient
relations in soilless grown strawberries needs to be further elucidated.
Keywords: fertilization, calcium, magnesium, nutrient leaching, soilless culture, strawberry
Introduction
The effect of major and minor elements on the fruit quality as well as their
accumulations in the organs of strawberries grown in the field and soilless culture was
reviewed by Nestby et al. (2004). A strawberry plant with unsatisfactory nutrient supply
can not produce the genetically determined fruit quality (M. Deák et al., 2007).
However, leaf dry matter analysis taken during beginning of flowering, could be used as
an indicator thus making it possible to make corrections within the season, if needed
(Daugaard, 2007). K is one of three major crop nutrients, with an essential role in
physiological processes such as water uptake, osmotic regulation, photosynthesis
enzyme action, and has been considered to have a significant role in decreasing effects
of climatic stress (Fodorné Fehér et al., 2007). As stated by Tagliavini et al. (2004), K
uptake has special features as more than 60% of total requirements are met in short
period of five weeks after flowering. It is well known that high supply with K can
influence Ca and Mg uptake in plants, but the possible influence of accompanying
anions on K, Ca and Mg interrelations were rarely investigated.
Recently, Rácz (2007) stated that the mean utilisation of main nutrient elements varied
between 30 and 80% in the open systems of experimental soilless cultures. However,
after Madjar and Davidescu (2004), the K retention and leaching process on organic
substrate with high organic matter content are not fully understood yet. Therefore, the
aim of the presented study was to evaluate the K level influence on strawberry nutrient
supply, considering possible impact of accompanying anions and the intensity of K loss
by leaching in soilless culture.
Materials and methods
The cold stored frigo plantlets (A4+) of strawberry (Fragaria x ananassa Duch. cv.
Elsanta) were planted on August 1, 2007, in perlite pot (4.5 l) filled with peat mix
1
(Stender B 400) and mount on vertical support structures (Figure 1), in plastic
greenhouse located in Dalj (40 km east from Osijek, Croatia). The number of pots per
vertical was 8 with 4 plants in every pot. Each vertical was supplied by one trickle
irrigation line, placed in the uppermost pot. In the vegetative stage all plants received in
total 0.41 g K plant-1, using complex fertilizer with microelements, with N : P2O5 : K2O
ratio 12 : 30 : 12 and 20 : 20 : 20, as well as fertilizer Universol Purple containing MgO
and microelements. On September 10, at the beginning of fruit set, the experiment with
4 potassium fertilization treatment was settled with 4 verticals (repetitions) per
treatment. Control plants (variant F1) received further 0.72 g K plant-1 as KNO3. The
variants F2 - F4 received triple dose (in total 2.22 g K plant -1 in period September 10 –
October 12), applied in 4 fertirigation treatments, in the same terms as control variant.
F1 was the combination of KNO3 and K2SO4, F2 was composed of KNO3 and KCl,
while F4 contained KNO3 and KHCO3. The ratio of KNO3 and other K salts
administered in nutrient solution was 1:2 in treatments F2 - F4. Plants received the same
Ca and Mg amount regardless of K treatment, whereas 1.5 g Ca plant-1 was applied
additionally in fruit bearing period. The percolated nutrient solution was collected using
PVC containers placed under the verticals before the applications of fertilization (Figure
1). The volume of the leached solution was measured and the concentration of K in the
solution was analyzed by AAS 24 h after the beginning of treatment. The most
developed strawberry leaves were sampled (30 leaves per vertical – repetition) before
the first fertilization treatment on September 10, as well as two days after the last
fertilization treatment, on October 12. The concentration of K, Ca and Mg in leaf dry
matter was determined by AAS, after leaf dry matter decomposition using acid mixture
(sulphuric and perchloric acid) and H2O2. During the experiment, fruits were harvested
every third day from each vertical (repetition) and the total yield was calculated and
expressed as g plant-1. Statistical data analysis was performed using single-factor
ANOVA, with F test for treatment influence evaluation and LSD test for treatments
means comparison, as well as t test in correlative regression analyses.
Results and discussion
According to the measured K concentration in percolated nutrient solution, it can be
concluded that higher K supply in nutrient solution resulted with significantly higher
leaching loss (P≤0.01), as compared to control treatment with 2.4 times lower K dose
(Table 1; Figure 2).
Table 1. The influence of the K fertilization treatments on K, Ca and Mg uptake and yield of strawberry (data
are means of four replicates; means followed by the same letter do not differ according to LSD test).
Fertilization
treatments
F1 (KNO3)
F2 (KNO3+K2SO4)
F3 (KNO3+KCl)
F4 (KNO3+KHCO3)
F test
Leaf nutrient composition
Applied
Leached
K g plant-1 K g plant-1
K%
Ca %
Mg %
1.13
0.18a
2.15a±0.09
0.74a±0.02 0.33a±0.01
2.64
0.51b
2.31a,b±0.09 0.71a±0.03 0.27b±0.00
2.64
0.46b
2.55b,c±0.06 0.71a±0.04 0.26b±0.00
2.64
0.51b
2.75c±0.08
0.70a±0.03 0.24b±0.02
Analysis of variance (* P≤0.05, **P≤0.01)
3.903*
14.007**
ns
6.021**
2
Fruit yield
g plant-1
73.8a±2.21
66.5b±1.80
64.4b±2.01
68.1a,b±1.59
4.376*
However, although the same K amount was given in F2 – F4, the percentage of lost K
per vertical was not equal (Figure 2). Among these treatments, the lowest leaching of K
was observed in F3 (the combination K-of nitrate and -chloride).
Rácz (2007) stated that as the ratio of nutrients depleted as well as left in the overflow
cannot be determined directly in the experimental production so that the volume of the
overflow could not be plotted against the nutrients taken up by plants. Accordingly, the
data presented show only the loss of the applied K that occured in 24 h after the applied
fertirrigation. In the research of Madjar and Davidescu (2004), the quantity of K that
passed through the organic substrate column without being retained or K in percolate
was 34-46% from the applied quantity of K. The content of nutrients in the drainage
water depends on the substrate, the addition of preplant fertilizer, the growth stage of
the plants, the percentage of drainage and the climatical conditions (Lieten et al., 2004).
19.38
20.0
19.14
Leached K (% of applied)
19.0
18.0
17.37
17.0
16.0
15.24
15.0
14.0
KNO3
KNO3+K2SO4
KNO3+KCl
KNO3+KHCO3
Fertilization variants
Figure 1. Collection of nutrient solution leachate
from strawberries grown in a vertical pot system in
plastic greenhouse
90
Figure 2. The amount of leached K per treatment
as % of the applied K per vertical
(data are means of four replicates)
0.4
3.0
2
2.6
60
2.4
50
0.3
% Mg
70
y = 0.0045x - 0.0904x + 0.4563
r = - 0.753**
0.3
2.8
Leaf K (% in DM)
K dose (g vertical-1)
80
0.3
0.2
2.2
40
added K
0.2
leaf K
30
1.7
2.0
KNO3
1.9
2.1
2.3
2.5
2.7
2.9
3.1
%K
KNO3+K2SO4 KNO3+KCl KNO3+KHCO3
K treatments
Figure 4. Leaf K and Mg antagonistic relation in
soilless grown strawberry under influence of
enhanced potassium supply in nutrient solution
(n=16; ** P≤0.01)
Figure 3. The variation of K % in strawberry leaf
dry matter under influence of K treatment
(data points are means ± S.E. of four replicates)
The enhanced K supply and the addition of sulphate, chloride or bicarbonate anions did
not altogether increase strawberry fruit yield. On the contrary, the highest yield was
obtained on control variant with lower K dose applied only as nitrate (Table 1). The
insignificantly lower yield per plant was in the combination with KCl (F3), in variant
that had the lowest leaching loss of K.
3
As stated by Tagliavini et al. (2004), nutrients entering the fruit during its maturation
derive only partially from direct root uptake, while significant amounts come from
leaves, in the latter, N and K contents may markedly decrease during fruit maturation if
not compensated by root uptake. Here, the enhanced K supply led to significantly higher
K concentration in strawberry leaves, especially in F3 and F4 (P≤0.01). Although the K
dose was much higher in F2 – F4 as compared to F1, leaf K concentration was different
regarding accompanying anion (Figure 3). In generall, K dose was not significant for Ca
concentration in leaf dry matter, but in the case of Mg, there was very significant
decrease under influence of K excessive supplly (Table 1; P≤0.01).
As reported by Lieten (2006), during the autumn culture of Elsanta on peat substrate,
the different K:Ca:Mg ratios in the nutrient solution did not affect vegetative growth or
yield. Regarding the leaf K and Mg concentration in the research presented here, there
was an antagonistic relation between these elements (Figure 4; P≤0.01), but the possible
role of accompanying anions in the uptake of K and Mg as well as other nutrients,
remains to be further investigated.
Conclusions
This research shows that rapid loss of the applied K in peat grown strawberry in vertical
pot system depends mostly on K rate. The higher fertilization level enhanced leaf K
concentration, depending on accompanying anions, yet without beneficial effect on fruit
yield. Based on leaf mineral composition, the antagonism in the uptake of K and Mg
was observed, while K did not affect Ca uptake. The role of accompanying anions in the
nutrient relations in soilless grown strawberries needs to be further elucidated.
Acknowledgements
This work was an integral part of the research project no.: 079-0790494-0559
(„Physiological mechanisms of plant tolerance to abiotic stress”) supported by The
Ministry of science, education and sports, Croatia.
References
Daugaard, H. 2007: Leaf analysis in strawberries: Effects of cultivar, plant age, and sampling time on nutrient
levels. Journal of Plant Nutrition, 30: 4-6. 549-556.
Fodorné Fehér, E., Varga, I., Fodor, L., Lefler, P. 2007: Stock fertilization with potassium in vineyard on
sandy soil. Cereal Research Communications, 35: 393-395.
Lieten, P. 2006: Effect of K:Ca:Mg Ratio on Performance of 'Elsanta' Strawberries Grown on Peat. Acta
Horticulturae ISHS, 708: 397-400.
Lieten, P., Longuesserre, J., Pivot, D. 2004: Experiences with substrates, drainage water and recirculation in
strawberry culture. Acta Horticulturae ISHS, 649: 207-211.
Madjar, R., Davidescu, V. 2004: Retention and migration process of potassium in an organic substrate for
horticulture. Acta Horticulturae ISHS, 633: 309-314.
M. Deák, Sz., Márk, G.I., Szabó, T., Füleky, Gy. 2007: Spectral properties of strawberry plants. International
Journal of Horticultural Science, 13 (2): 17–22.
Nestby, R., Lieten, F., Pivot, D., Raynal Lacroix, C., Tagliavini, M., Evenhuis, B. 2004: Influence of mineral
nutrients on strawberry fruit quality and their accumulation in plant organs. A review. Acta Horticulturae
ISHS, 649: 201-206.
Rácz, I. 2007: Study on nutrient conditions in soilless vegetable production. Cereal Research
Communications, 35: 965-968.
Tagliavini, M., Baldi, E., Nestby, R., Raynal-Lacroix, C., Lieten, P., Salo, T., Pivot, D., Lucchi, P.L.,
Baruzzi, G., Faedi, W. 2004: Uptake and partitioning of major nutrients by strawberry plants. Acta
Horticulturae ISHS, 649: 197-200.
4