THE INFLUENCE OF SYNTHETIC FERTILIZERS ON SEED GERMINATION AND EARLY GROWTH OF HORDEUM VULGARE L.
DOI:10.30825/5.EJPAU.28.2017.20.4

Ali Asghar Aliloo
Department of Plant Production and Genetic Engineering, Faculty of Agriculture, University of Maragheh, Iran

ABSTRACT

Experiments were carried out to evaluate synthetic fertilizers effects on seed germination and seedling growth of barley (Hordeum vulgare L.). In this study, three most commonly used synthetic fertilizers including Urea (100, 200, 300, 400, 500 and 1000 ppm), Triple superphosphate (10, 20, 30 and 60 ppm) and K₂SO₄ (100, 200, 300, 400 and 800 ppm) were used in four replications. The results showed that fertilizers at given concentrations did not change seed germination performance. However, there was a significant influence on seedling performance. Seedling growth under Triple superphosphate and K₂SO₄ applications was slightly enhanced, but the enhancement for Urea was notice only at low concentrations. At high concentrations the seedling growth significantly decreased in comparison with control. The root to shoot ratio was influenced by Urea and when the concentrations exceeded 300 ppm the ratio was decreased. The results also showed that Triple superphosphate improved root dry weight, but the other treatments decreased this trait slightly. It was concluded that the seedling growth of barley was more sensitive than seed germination to the fertilizers, and among the treatments Urea application due to inhibition effects at high concentrations must be used carefully.

Key words: Fertilizers, Germination, Hordeum vulgare, Seedling growth .

INTRODUCTION

Hordeum vulgare L. (Poaceae) is one of the first cultivated cereals that has been commonly used for multiple purposes such as food, animal fodder and beverages. According to FAO statistics [10] the average production of the crop in Iran is about three million tons per year covering 70% of the country requirements. In grain crops, seed germination and early seedling growth are very vulnerable to environmental stresses. The success at these stages could enhance crop growth and development, so the plants survive under environmental stresses to better production [1, 2]. Beside environmental stresses, the inputs such as synthetic products that frequently are used in agro-systems have a great potential to influence the germination processes. Main synthetic inputs are fertilizers, insecticides and herbicides that could be a stress source for seed germination. Nowadays, yield has been mostly increased by fertilizers [9]. Fertilizers are superior tools to enhance productivity; however, they have disadvantages such as eutrophication [17], increase soil acidity and impact on flora and fauna [4]. Concurrency application of synthetic fertilizers with seed germination and seedling growth could adversely affect these processes. Various tests have reported conflicting effects of fertilizer on seed germination. For example, Bremner [6] reported that application of Urea in soil had an adverse effect on germination of wheat, rye and corn. They also stated that this effect is imposed indirectly by ammonia as a result of urease activity, while Durrant and Mash [8] found that potassium nitrate increased hypocotyl growth of sugar beet seedling. Dürr and Mary [7] also determined that absorption of minerals were different among species. According their findings, absorption of nitrogen by sugar beet started earlier than by wheat seedling, which affect hypocotyl elongation. Another important issues at germination time and seedling growth is water potential of the seed bed [13]. Commonly, decreasing the water potential as a result of dissolved salts could affect root protrusion and seedling growth. Bouaziz and Hicks [5], however, reported that relationship between water potential and seed germination of wheat seed was not significant. There is a necessity to distinguish the effects of supplementary synthetic fertilizer on germination and emergence for better understanding these contradictory effects.

The objectives of the study were: (a) to determine the effects of most used synthetic fertilizer on germination and seedling growth of barley and (b) to evaluate the seedling vigor performance under different fertilizer application.

MATERIAL AND METHODS

This study was conducted at Agronomy Laboratory of University of Maragheh, Iran in a completely randomized design (CRD) with four replications during the year 2015. The used barely variety was Hordeum vulgare var. Sardari (widely cultivated in North West of Iran). In order to disinfection, the seeds were surface sterilized with 1% of sodium hypochlorite for 10 minutes, followed by washing with tap water for three minutes. Seeds were immediately surface dried by filter paper. Twenty five seeds were placed on two layers of filter paper then the following fertilizer solutions include: Urea (100, 200, 300, 400, 500 and 1000 ppm), Triple superphosphate (10, 20, 30 and 60 ppm) and K₂SO₄ (100, 200, 300, 400 and 800 ppm) were poured (10 ml) on the seed bed. The used concentrations imitate possible status of the fertilizers in the soil solutions. To prevent drying of seed beds, the rolled filter papers were put in plastic bags and were kept in the germinator maintained at 20°C. After 10 days towel papers were removed and characteristics including germination percentage (GP%), normal seedling percentage (NS%), root length (RL), shoot length (SL), seedling length (SEL), root to shoot ratio (R/S), dry weight of root (WR), dry weight of shoot (WS) and seedling dry weight (WSE) were recorded. To calculate seedling vigor index (SV) we used the following formula:

SV = [(G/G0) × (SEL/SEL0)]

Where:

G – percentage of germinated seeds in the treatment;
G0 – percentage of germinated seeds in the control;
SEL – average length (cm) of the seedling in the treatment;
SEL0 – average length (cm) of the seedling in the control.

For the statistical analysis, the data of germination percentage was transformed to .

RESULTS

Results concerning to Table 1 and 2 showed that the effects of synthetic fertilizers on traits including root length (RL), seedling length (SEL), root to shoot ratio (R/S), dry weight of root (WR) and vigor index (SV) were statistically significant (p≤0.01). However, germination percentage (GP%), normal seedling percentage (NS%), shoot length (SL), dry weight of shoot (WS) and seedling dry weight (WSE) were not remarkably affected by fertilizers application. The findings showed that fertilizer at given concentration did not alter germination percentage. In this study, shoot length slightly increased when K₂SO₄ and Urea were used at low and medium concentrations, while at the highest concentrations the rate decreased smoothly (Tab. 1). According to Table 1, at high concentrations of the synthetic fertilizers, a non-significant inhibitory effect was recorded for shoot growth. Root growth was remarkably influenced by fertilizers and at 300–400 ppm of K₂SO₄ and 30 ppm Triple superphosphate the value was noticeably increased in comparison with the control treatment, however the enhancing effect for Urea was not achieved, nevertheless, low concentrations i.e. 100 and 200 ppm smoothly improved the rate. Contrary, with increasing Urea concentration up to 400 ppm the root growth significantly decreased compared to the control (Tab. 1, Fig. 1). Almost, similar results were also recorded for seedling length. The highest seedling growth was obtained by K₂SO₄ at 400 ppm concentration which had no significantly differences with control. On the other hand, Urea at the highest concentration (1000 ppm) reduced the value considerably (Tab. 1). Root to shoot ratio was slightly improved by Triple superphosphate treatments but high concentrations of Urea (400–1000 ppm) declined the ratio significantly (Fig. 2). Regarding Table 2, the shoot and seedling dry weights were not significantly affected by treatments, however, the treatments had influence on root dry weights. Compared to the control, Triple superphosphate had a positive influence on root dry weight (Fig. 3); whereas the others decreased the value and the lowest values were measured for Urea treatments at high concentrations (Tab. 2). The results of seedling vigor index revealed that the fertilizers have significantly influenced on the index (Tab. 2). At medium concentration of K₂SO₄ and Triple superphosphate the index was slightly improved and highest value was obtained by K₂SO₄ at 400 ppm concentration. However, amendment of Urea was seen at first two low concentrations. At highest concentration of Urea the index was significantly decreased in comparison with control treatment (Tab. 2).

DISCUSSION

The study revealed that the synthetic fertilizers did not affect seed germination of barley (Tab. 1). These findings are in consistence with Monaco et al. [16], who studied the influence of N form and availability on germination and seedling development of two invasive annual grasses and six perennial grasses. They found that treatments did not alter germination percentage. The results of germination experiment also agreed with those of other studies on soil N effects, demonstrating modifications in soil N do not alter seed germination of many grass and broad leaf weed species [15]. They also suggested that the presence of N in seed bed environments only alters germination of dormant seeds. In our study, the dormancy was not observed and all of seeds in control treatments were germinated. Some experiments reported that ammonia toxicity as a result of Urea volatilization could be effective on germination of rice [18]. However, in our study the toxicity of the fertilizers at used concentrations on seed germination did not confirm this effect. It is possible that at higher concentrations the inhibition effects inaugurate and seed germination percentage reduces severely. Again, there was also no difference between the fertilizers and control on abnormal seedlings perhaps supporting the safety of used concentrations. Under synthetic stresses, usually the number of abnormal seedling in crop plants tend to be increase [3] and it`s rate depends on synthetic concentrations and exposure duration. Hadžić [12] reported inhibition in seedling growth of Setaria glauca when synthetic fertilizers reached up to 1%. Regarding to our findings, the fertilizers did not alter shoot growth of the plant while their effects on root growth was significant. The concentrations of K₂SO₄ and Triple superphosphate enhanced the root rate, however, Urea only at the low concentrations showed better results and at higher concentrations inhibition effects were recorded. There were similar results for root dry weights but Triple superphosphate was superior for this trait. These findings are agreed with other published results. Anatomical and biochemical analyses of Arabidopsis thaliana have shown that low-P-grown mature roots absence a typical apex. By contrast, the roots of high-P-grown plants have high auxin contents in meristematic cells with high mitotic activity [11, 14]. Regulation in root growth by P in our study may be related to mitotic activity at root region which enhanced root dry weights. There was no significant change in seedling dry weight. With regarding the change in root dry weight, the results revealed that allocation of reserves to root parts under P rich environments was promoted (esp. root thickness improved) while Urea decreased root to shoot ratio, especially at higher concentrations. Fertilizers did not improved seedling vigor index but they decreased the value at high concentration. Lowest seedling vigor index was achieved at higher concentration of urea. We used the multiplication of seed germination and seedling behavior to calculate the seedling vigor index. Seed germination parameter was not significantly affected by fertilizers in comparison to control, therefore the results of the index was similar to the seedling measurements.

CONCLUSIONS

In conclusion, it is not easy to make simple recommendations on fertilizer safety on seeds germination and early growth of barley. The rates of nitrogen, phosphorus and potassium fertilizers did not affect seed germination percentage, however, seedling values, especially root parts, were decreased at high concentration of the fertilizers. Suggesting this fact that seedling developments are more susceptible than seed germination processes to chemical fertilizers. This research revealed that Urea at high concentration could decrease the root growth and consequently the modifications will occur in root to shoot ratio.

REFERENCES

Accepted for print: 10.10.2017

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.