Potassium Rate and Accompanying Anions Impact on POTASSIUM, Calciumand MAGNESIUM Uptake

potassium rate and accompanying anions impact on POTASSIUM, cALCIUMAND MAGNESIUM uptake by strawberries in soilless culture

Miroslav LISJAK1 – Aleksandar STANISAVLJEVIĆ1 – Marija ŠPOLJAREVIĆ2 –Boris ĐURĐEVIĆ1

1Department of agroecology, Faculty of agriculture, University of J.J. Strossmayer, Trg Sv. Trojstva 3,

31 000 Osijek, Croatia, e-mail:

2 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 retentionand 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 (Stender B400) 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 wassupplied 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-1was 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 solutionwas 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).

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).

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.

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 lossof 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 onaccompanying anions, yetwithout 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 theresearch project no.: 079-0790494-0559 („Physiological mechanisms of plant tolerance to abiotic stress”) supported by The Ministry of science, education and sports, Croatia.

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