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Article

Influence of Mineral Liquid Fertilization on the Plant Growth of Perennials on Sheep’s Wool–Coir–Vegetation Mats

by
Susanne Herfort
1,2,*,
Virginia Maß
3,
Amelie Hüneburg
4 and
Heiner Grüneberg
5
1
Albrecht Daniel Thaer-Institute of Agricultural and Horticultural Sciences, Faculty of Life Sciences, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
2
Institute for Agricultural and Urban Ecological Projects (IASP) Affiliated to Humboldt-Universität zu Berlin, 10115 Berlin, Germany
3
Leibniz Institute for Agricultural Engineering and Bioeconomy Potsdam-Bornim (ATB), Department of Agromechatronics, 14469 Potsdam, Germany
4
Bundesverband GebäudeGrün e.V. (BuGG), 10115 Berlin, Germany
5
Division Urban Ecophysiology of Plants, Albrecht Daniel Thaer-Institute of Agricultural and Horticultural Sciences, Faculty of Life Sciences, Humboldt-Universität zu Berlin, 14195 Berlin, Germany
*
Author to whom correspondence should be addressed.
Horticulturae 2024, 10(8), 773; https://doi.org/10.3390/horticulturae10080773
Submission received: 28 May 2024 / Revised: 1 July 2024 / Accepted: 8 July 2024 / Published: 23 July 2024
(This article belongs to the Special Issue Cultivation and Breeding of Ornamental Plants)
Browse Figures
Versions Notes

Abstract

:
Perennials are usually pre-cultivated on vegetation mats consisting of coconut fiber (coir), which require weather-dependent irrigation and regular fertilization with fast-acting fertilizer to achieve a saleable condition as quickly as possible. In the pre-cultivation of sheep’s wool–coir–vegetation mats, nitrogen (N) is already sufficiently contained in the vegetation mats due to the natural nitrogen content of the sheep’s wool fibers, so that additional liquid fertilization during pre-cultivation can be dispensed with if necessary. In this study, sheep’s wool–coir–vegetation mats of 4.5 kg/m2 were pre-cultivated with 16 perennial plants (8 species) in 2018. Variant 1 (V1) received regular fertilization with mineral liquid fertilizer (total 8.7 g N/m2) during pre-cultivation. Variant 2 (V2) was not fertilized during pre-cultivation. In spring 2019, all pre-cultivated vegetation mats were lifted and laid on an area prepared with topsoil. No additional fertilization was applied after laying. The overall impression, plant height, number of flowering perennials, and plant coverage were examined in the 2018 and 2019 growing seasons, with only minor differences observed between V1 and V2. The number of flowers, biomass, and nitrogen content were determined for the two aster species used. There were differences between V1 and V2 in 2018, but not in 2019. The coverage of perennials of 50%, which is the prerequisite for the saleability of the vegetation mats, was already achieved on both V1 and V2 after 4 months of pre-cultivation. The overall impression of the perennials on both V1 and V2 also did not differ during pre-cultivation nor in the following year. Therefore, liquid fertilization is not necessary during the pre-cultivation of perennials on sheep’s wool–coir–vegetation mats.

Graphical Abstract

1. Introduction

Due to the global growth in the urban population and the associated increase in soil sealing and urban sprawl, sustainable urban development is becoming increasingly important. Forecasts show that 60% of the world’s population will be living in cities by 2030 [1]. The fact that green spaces are indispensable in cities is demonstrated by their multifunctionality: they can absorb pollutants from the air, reduce air pollution and noise [2], contribute to cooling the air, retain water, and counteract the heat island effect [3,4,5,6]. However, it should also be noted that the urban climate is changing significantly with the increase in climate change [7,8]. Strategies for urban green spaces to adapt to climate change are therefore necessary and are being pursued worldwide [9,10,11,12]; these include the creation of additional green spaces on buildings [13,14].
In urban areas, the creation of green spaces, with plants that are suitable for their location and require low maintenance, is an option as described by Hansen et al. [15]. However, it is a major challenge for plants to adapt to climatic changes. Studies on the extreme temperature events observed in Germany over the last 50–130 years clearly show that the maximum temperature is shifting towards higher extremes and the minimum temperature is tending towards less extreme values. This can also be observed in the decline in frost days. Overall, precipitation totals decreased slightly on average in Germany in the summer, with an increase in days with heavy precipitation [16]. Regarding the future management of green spaces in urban areas, this means choosing planting systems that can store sufficient water and provide the plants with sufficient nutrients over a longer period of time. The use of pre-cultivated vegetation mats with sheep’s wool has already been described by Herfort et al. [17] and offers the advantages that the coverage of the planting when laying the vegetation mats is higher than the coverage of new planting, and that the plants have already established themselves. Additionally, the vegetation mats made of sheep’s wool contain sufficient plant-available nutrients that act as long-term fertilizers and can be released to the plants over a longer period of time. Vegetation mats made of sheep’s wool and coir can store up to 82% (by volume) of rainwater [17], which is an advantage for a functioning urban greening—and also for green roofs [18,19,20].
Mixed perennial plantings are increasingly desirable in urban areas, as they are stress-tolerant [21], but above all, they are aesthetic and perennial [15,22,23]. Native plantings with extensive maintenance requirements are the main focus of greening in urban areas [24]. The advantage of using perennials is that they can live for up to 20–25 years [15], eliminating the need for costly alternating plantings that have to be replaced several times a year [24]. Reducing the maintenance effort reducing complexity and permanent plantings is required in order to be cost-efficient [25]. The flowering ability of perennials [26,27] is not inferior to the flowering ability of the alternating plantings, so the benefits of perennials also extend to insects. The “Bund deutscher Staudengärtner” (Association of German Perennial Growers) has now compiled 43 promising perennial mixes for a wide variety of locations in Germany [28].
The cost-effectiveness of planting and maintaining green spaces also plays a major role due to the ever-shrinking budgets of cities. On a positive note, prefabricated, site-specific perennial mixes eliminate the planning effort required for alternating plantings [26]. However, fertilizing is essential, especially for perennials with high nutrient requirements. When maintaining urban green spaces, the recommendation for Berlin (Germany) is to give preference to organic slow-release fertilizers [27]. The sheep’s wool in the vegetation mats would be suitable for this.
The hypothesis of this research is that no application of liquid fertilizer is necessary during the pre-cultivation of vegetation mats with raw sheep’s wool and coir. The hypothesis is, furthermore, that plant growth, especially after laying the vegetation mats, is independent of additional fertilization during pre-cultivation due to the nitrogen contained in the sheep’s wool fibers. Additionally, the question is whether the selected perennials are suitable for sheep’s wool mats. The background to this study is the great demand for local products in horticulture. Sheep’s wool, which is available worldwide, could therefore be used for planting concepts in public green spaces in every region of the world.

2. Materials and Methods

2.1. Utilized Sheep’s Wool–Coir–Vegetation Mats and Their Properties

Based on Herfort et al. [17], vegetation mats were developed that consist of mixed fleeces of raw sheep’s wool and coir with a fiber ratio of 1:1. Before the fibers were processed, the raw wool was hygienized according to a standard hygiene procedure [29] (Koch GbR, Waiblingen, Germany). After hygienization, the wool was air-dried and shredded using a shredder specially developed for raw wool (Ralle Landmaschinen GmbH, Großvoigtsberg, Germany). The sheep’s wool fibers were then mixed with the coir and processed into vegetation mats [17].
In the experiment, four vegetation mat variants of 1 m × 1 m were tested in 12 replicates. In this study, two variants are evaluated: fertilized (V1) and non-fertilized (V2) thick-layer vegetation mats. Plant growth was best on the vegetation mat variants V1 and V2. V3 (thin-layer sheep’s wool–coir–vegetation mat) and V4 (coir–vegetation mat) were not considered. The vegetation mats V1 and V2 were reinforced on both sides with a coir fabric (basis weight of 400 g/m2). The average fiber weight of the mat types V1 and V2 was 4.5 kg/m2. The vegetation mats were manufactured by the company MST-Dränbedarf GmbH (Twistringen, Germany).
The nitrogen content of the sheep’s wool and coir used was analyzed according to the VDLUFA II.1, 3.5.2.7 (2000) method [30] with a threefold repetition.

2.2. Experimental Conditions during Pre-Cultivation

The investigations of the pre-cultivation of the perennial mats with liquid fertilization and after their lifting and laying were carried out on the open space of the Albrecht Daniel Thaer-Institute of the Humboldt-Universität zu Berlin in 14195 Berlin-Dahlem (geographical coordinates: 52°28′ N; 13°18′ E). The experimental site belongs to the northeast German lowlands and is 51 m above sea level.
Due to its eastern location, the prevailing temperate climate at the experimental site is characterized by the transition from the maritime to the continental climate zone. The temperatures between July and December 2018 were on average 2.1 K higher, and between January and October 2019 were 2.0 K higher, than the 30-year average (1981–2010) for Berlin-Dahlem. Between July and December 2018, Tmax was 37.4 °C and Tmin was −1.3 °C. Between January and October 2019, Tmax was 39.2 °C and Tmin was −6.6 °C. Precipitation was 57% (170 mm) of the 30-year average between July and December 2018 and 79% (374 mm) of the 30-year average between January and October 2019. Global radiation was 112% (1838 MJ/m2) of the 30-year average between July and December 2018 and 88% (3039 MJ/m2) of the 30-year average between January and October 2019 [31].

2.3. Selection of Perennials

The young plants used for pre-cultivation were pre-grown in standardized P9 pots (0.5 L) [32] and supplied by the perennial nursery (Lux-Staudenkulturen, Pirna, Germany). Eight different types of perennials with different plant heights and flowering times were used (Table 1). All perennials showed a uniform growth pattern and had a uniform height depending on the type of perennial. The trial was carried out with perennials that prefer a sunny to semi-shady location.

2.4. Pre-Cultivation and Laying the Vegetation Mats with Subsequent Completion Care and Maintenance Care

At the end of June 2018, the vegetation mat variants of 1 m2 each to be tested were randomly laid in 12 replicates on an experimental site with woven tape fabric and perforated film on top (Figure 1a). Then, 16 planting holes were cut into each mat. On 11 July and 12 July 2018, the 8 different perennials were planted in duplicate in the mats and pre-cultivated in Berlin-Dahlem until 10 October 2018. The pre-cultivated mats were then left on the pre-cultivation area to overwinter.
On 2 April 2019, the vegetation mats were lifted and then laid on a prepared area with 10 cm of topsoil. The arrangement of the mats during laying corresponded to the arrangement of the pre-cultivation. After laying the mats, a 0.5 m wide mulch film was laid around the area to protect against weed pressure. From the time the mats were laid, completion care and maintenance care were carried out until October 2019 (Figure 1b).

2.5. Pre-Cultivation Conditions and Conditions during Completion Care and Maintenance Care

Irrigation was carried out using a drip irrigation system (NETAFIM Deutschland GmbH Innovative Bewässerung, Frankfurt/Nieder-Erlenbach, Germany) depending on the weather conditions and in accordance with irrigation recommendations [34], with all mats being treated equally. The V1 vegetation mats were fertilized weekly during pre-cultivation with a balanced mineral N-P-K liquid fertilizer (1st fertilization, mixed fertilizer in a ratio of 1:1 consisting of Kristalon® Azur: 16-11-16, Yara GmbH & Co. KG, Dülmen, Deutschland, and Kristalon® Grünmarke: 18-18-18, Yara GmbH & Co. KG, Dülmen, Deutschland; 2nd–6th fertilization, Agriplant 1: 20-5-10+2, Hauert MANNA Düngerwerke GmbH, Nürnberg, Deutschland). The fertilizer solution was prepared as follows: For the 1st fertilization, 0.5 kg Kristalon® Azur and 0.5 kg Kristalon® Grünmarke; for the 2nd–6th fertilization, 1 kg Agriplant 1 dissolved in 10 L tap water. The 1st fertilization took place on 10 August 2018, with 0.7 g N/m2, and the 2nd–6th fertilizer application was carried out weekly, with 1.6 g N/m2 per fertilization. Between 10 August 2018 and 14 September 2018, 8.7 g nitrogen per m2 was applied to V1 vegetation mats. The V2 vegetation mats did not receive any liquid fertilizer.

2.6. Data Collection

The perennials were evaluated every 2 weeks (7 assessments) from July to October 2018 and every 4 weeks (7 assessments) from May to October 2019. The overall impression of the perennials (see below), the plant height, the number of flowering plants and the number of flowers on the asters were examined. The above-ground fresh and dry mass and the resulting dry matter of the asters as well as the nitrogen content of the asters after pruning in October 2018 and after pruning in October 2019 were also examined. The coverage of perennials on the vegetation mats was recorded as part of the last assessment in October 2018 and as part of the 4-week assessments in 2019 that took place from the laying of the vegetation mats in April 2019.
The overall impression of the perennials was determined by awarding a score, according to [35] (score 1 = plant failure, score 3 = sufficient, score 5 = satisfactory, score 7 = good, score 9 = very good). As the assessment were carried out at different times; the developmental stage of the different plant species was considered. The possibility of a future increase in the overall impression was factored in and considered in the valuation. The observations were always carried out by the same person.
The plant height (stem height) was measured using a folding rule with a measuring accuracy of 0.5 cm.
The flowering period was determined by counting the plants that were flowering at the time of the assessment. In addition, the exact number of flowers on the asters was determined.
The determination of the above-ground fresh and dry mass was carried out exclusively for the asters and with digital scales (EMB 2000-2 and PCB M Memory, Kern and Sohn GmbH, Balingen-Frommern, Deutschland), as these were the only plants with a high biomass in the autumn and that could tolerate pruning. To determine the dry mass of the asters, the fresh mass was weighed and, in a first step, dried at 60 °C to constant weight in drying ovens (Thermo Scientific Heraeus® Series 6000 and HerathermTM OMH750, Fisher Scientific GmbH, Schwerte, Germany). After the nitrogen analysis, the samples were further dried in a drying oven (Memmert UM 400, Memmert GmbH, Schwabach, Germany) at 105 °C in a second step to determine the exact dry mass. Then, the dry matter was calculated.
The determination of the total nitrogen content in the above-ground dry mass of the asters was carried out according to Kjeldahl [36].
The coverage of the perennials on the vegetation mats was assessed on site and given in %.

2.7. Statistical Analysis

The median was calculated with SPSS (29.0) for the evaluation of the ordinal-scaled scores regarding the assessment of the overall impression depending on the vegetation mat variant V1 and V2. The plant height, the number of flowering perennials, the number of flowers on the asters as well as the above-ground fresh and dry mass and the dry matter calculated from these, the nitrogen content of the asters, and the coverage of the perennials on the vegetation mats were evaluated using analysis of variance (ANOVA) with SPSS (29.0).
Significant differences were determined with the Tukey’s test at a significance level of p < 0.05 [37]. Different lower-case letters in the tables indicate significant differences.
The mean variability was indicated by the standard error, which is marked with “±”, respectively, with error bars.
A linear correlation was calculated using Pearson correlation (r) to identify the relationships between the dry mass and the dry matter of the asters and between the nitrogen content of the above-ground dry mass and the number of flowers of the asters. These were confirmed at a significance level of p < 0.05.

3. Results and Discussion

3.1. Nitrogen Content of the Vegetation Mats

The total nitrogen content at the start of the experiment was 10.5% in the sheep’s wool fibers and 0.3% in the coir in the air-dry condition. The subsequently calculated nitrogen content (long-term available nitrogen) in the thick-layer vegetation mats averaged 241.8 g N (V1) and 245.5 g N (V2) per m2 of vegetation mat (Table 2). Cut perennials have a maximum N requirement of 25 g N/m2 per year [38]. The nitrogen depot in the vegetation mats could therefore, theoretically, last for around 10 years. But the biodegradation of the vegetation mats was not investigated. However, it was observed during the experiment that the biodegradation of the sheep’s wool–coir–mats was much slower than in composting or soil excavation, where a higher microorganism activity is recorded due to the prevailing ideal living conditions for fungi and bacteria [39,40,41]. During pre-cultivation, there was very low biodegradation of the vegetation mats due to the sealing of the soil with a film. It was found that the vegetation mats still had the mat structure in April 2019 and could be lifted. After laying the vegetation mats on the prepared area with topsoil, the perennials were able to root into the topsoil. The biological activity of the vegetation system therefore increased. Nevertheless, the mat structure was still completely present after the second year of the experiment. In future, the biological decomposition of the vegetation mats will have to be investigated in detail to determine when the fertilizing effect of the sheep’s wool will be exhausted.

3.2. Overall Impression of the Perennials

The overall impression of the perennials across all seven assessment dates in 2018 was “7” for V1 and V2. Nevertheless, there were small differences between V1 and V2 for Aster dumosus ‘Silberball’, Buphthalmum salicifolium, and Festuca glauca. Here, the scores for V1 were one level higher than for V2 (Table 3). Aster dumosus ‘Silberball’ and Festuca glauca also achieved the highest achievable score of “9” on the V1 mats. Buphthalmum salicifolium was the lowest, with a score of “5” (V1) and “3” (V2). This may be due to an excessive supply of nutrients, as Buphthalmum salicifolium prefers a lean soil [42]. For the remaining five perennial species, no differences between V1 and V2 were observed regarding the scoring. The score was “7” in each case.
After laying the vegetation mats in April 2019, a good plant appearance was again observed on all seven assessment dates in 2019 (Table 4). The overall impression of all perennials was “7” for V1 and V2 across all assessment dates in the 2019 experimental period. There were no differences in the overall appearance. Nevertheless, Anemone sylvestris, Festuca glauca, and Heuchera micrantha ‘Palace Purple’ showed a better overall impression on V1. There were no differences in the other five perennial species regarding the vegetation mat variant. A good to very good overall impression was achieved by seven out of eight perennial species on V1 and five out of eight perennial species on V2. The greatest differences were found with Anemone sylvestris. This could be because Anemone sylvestris, as a young plant during pre-cultivation, needs the additional nutrients from the liquid fertilizer to build up and start the winter season stronger. Further studies beyond 2019 would have been necessary here to better determine the effects of the long-term fertilization effect of sheep’s wool on Anemone sylvestris.
The overall impression of the perennials plays an important role in their saleability. For this reason, the median score of all plants was examined in more detail on the last assessment date of pre-cultivation in 2018. It was found that the median score of all perennials on the last assessment date in October 2018 was “7“ for V1 and “5“ for V2. For V1, 61% of the perennials, and for V2, 30% of the perennials, had a good to very good overall impression (Figure 2a).
On the last assessment date in October 2019, the median score of all perennials on V1 was “9” and on V2 it was “7”, which indicates very good to good development of the perennials on both vegetation mat variants after the soil-bound layering in April 2019. In October 2019, 71% achieved a good to very good overall impression on V1 and 67% on V2 (Figure 2b).
The plant failures mainly affected Achillea clypeolata ‘Moonshine’ and Buphthalmum salicifolium. It is assumed that the perennials were planted too close together at 20 cm. A plant spacing from 40 cm to 50 cm is advantageous for Achillea clypeolata ‘Moonshine’ and from 30 cm to 40 cm for Buphthalmum salicifolium, so that the perennials can develop fully [33]. In the future, therefore, fewer plants should be planted per m2. Another reason for the low scores for Achillea clypeolata ‘Moonshine’ and Buphthalmum salicifolium could be that the perennials were planted without taking sociability into account. Achillea clypeolata ‘Moonshine’ and Buphthalmum salicifolium have a sociability class of I [33]. They should, accordingly, be planted individually or in small tufts, which could not be considered in the experimental design. In addition, the vegetation mats made of sheep’s wool and coir rarely dry out completely due to their good water retention, which can be disadvantageous for dry-loving perennials.
On a positive note, the overall impression of the perennials on V2 between the last assessment date in 2018 and the last assessment date in 2019 approached the very good overall impression of the perennials on V1, which is due to the slow onset of the fertilizing effect of the sheep’s wool in the second year [43], when the degradation of the sheep’s wool mats on the soil is lower than it is in the soil due to the lower biological activity.

3.3. Plant Height of the Individual Perennials

A positive development of perennials is also characterized by the plant height. But significant differences in terms of stronger height growth in the first year of cultivation in October 2018 were only observed for Achillea clypeolata ‘Moonshine’ and Festuca glauca. On V1, the plant height of Achillea clypeolata ‘Moonshine’ was 25% higher and that of Festuca glauca was 31% higher than on V2 (Table 5). However, the application of liquid fertilizer during pre-cultivation could be dispensed with, as stronger height growth was only observed in two out of eight perennials.
After laying the vegetation mats at the end of the 2019 experimental period, it was found that there were only differences in plant height for Anemone sylvestris (on V1, 29% higher than on V2) and Festuca glauca (for V1, 12% higher than on V2) (Table 6). No differences were found in the height growth of the other six perennial species. All perennials, regardless of whether they were fertilized or not fertilized during pre-cultivation, were within the normal range in terms of growth height (Table 1), so it can be concluded that, for V2, the perennials were also well supplied with nutrients by the sheep’s wool mats on during the first and second years of the experiment and that liquid fertilization is not necessary during pre-cultivation.

3.4. Flower Formation of the Individual Perennials

Cultivation measures such as fertilization serve to vitalize the plants and stimulate flower formation [44]. For the perennials examined, liquid fertilization during pre-cultivation had the following effects:
Achillea clypeolata ‘Moonshine’ did not flower on V1 nor on V2 during pre-cultivation in 2018 due to the juvenile stage. The second year showed that flowering lasted from June to October 2019 and went far beyond the specified period from June to July (Table 1 and Figure 3). In July 2019, 71% of the plants on V1 and 88% of the plants on V2 were flowering. At the last assessment date in October 2019, 50% of the plants on V2 and 1% of the plants on V1 were still flowering. Finally, 83% of the plants flowered on V1 and 96% on V2. It becomes clear that Achillea clypeolata ‘Moonshine’ does not require any additional liquid fertilization during pre-cultivation and that liquid fertilization tends to inhibit flowering, which is in accordance with Rünger [45]. The supply of nutrients from the sheep’s wool is sufficient for long-lasting flower formation in the year following the laying of the vegetation mat. The supply of nutrients from the sheep’s wool combined with long-lasting flower formation in the year following the laying of the vegetation mats is sufficient.
Anemone sylvestris, like Achillea clypeolata ‘Moonshine’, did not flower in 2018 due to its stage as a young plant. In 2019, Anemone sylvestris flowered over two periods, once in May and once from July to October (Figure 4), which is positive. Anemone sylvestris usually flowers from May to June (Table 1). There were differences between V1 and V2 regarding the number of flowering plants, in that 42% of the plants on V1 and 25% of the plants on V2 ultimately flowered, which may be due to the fact that the juvenile stage had not yet been concluded for all plants. However, it could also be that the supply of nutrients was too high and/or the vegetation mats were too moist during the young plant stage. The study period for assessing the flowering capacity of the perennials should have been longer. Later, in 2022, a very strong flower formation was observed in Anemone sylvestris, which indicates an optimal nutrient supply from the vegetation mat. However, the year 2022 was not the subject of the investigations. Nevertheless, the test results clearly showed that Anemone sylvestris does not benefit from additional liquid fertilization during pre-cultivation in terms of flowering ability.
Buphthalmum salicifolium did not flower during pre-cultivation in 2018 due to the juvenile stage, but it did flower in the second year between June and October 2019. Each plant flowered on both the V1 and V2 vegetation mats (Figure 5), even beyond the usual flowering period (Table 1). The peak of flowering was in July 2019 (V1, 95% of the plants; V2, 94% of the plants). In August 2019, there was a slight decrease in flowering plants, followed by an increase again. At the end of the 2019 experimental year, 63% of the plants on V1 and 50% of the plants on V2 were flowering. There were always more plants flowering on V1 than on V2, although Buphthalmum salicifolium prefers a lean medium [42]. However, the differences between V1 and V2 were small, suggesting that liquid fertilizer application during pre-cultivation is not necessary.
Festuca glauca did not flower in 2018 due to being in the juvenile stage, but in the second year, between May and October 2019 (Figure 6), all plants flowered on both V1 and V2, a result that coincides with or exceeds the usual flowering period of Festuca glauca (Table 1). Liquid fertilizer is not required during pre-cultivation.
Fragaria vesca flowered despite the young plant stage over the 2018 experimental period; 75% of the plants flowered on V1 and 62% flowered on V2. The peak of flowering was observed on V1 on 14 August 2018. At this time, 54% of the plants on V1 were flowering. The plants on V2 were delayed in flowering, which indicates that without liquid fertilization, the flowers were formed later. In 2019, all plants on both V1 and V2 flowered. This indicates a uniform release of nutrients from the sheep’s wool (Figure 7) and corresponds to the usual flowering period from May to June (Table 1).
Heuchera micrantha ‘Palace Purple’ started flowering in July 2018. At the peak of flowering in August 2018, 100% of the plants on both V1 and V2 were in flower (Figure 8). The flowering period lasted until October 2018, which is longer than the usual flowering period until August (Table 1) and indicates a good nutrient supply. In 2019, 79% of the plants flowered on V1 and 88% on V2. In August 2019, which was the peak of flowering, 67% of the plants on V1 and 83% on V2 flowered, whereas in September, 63% of the plants on V1 and 50% on V2 flowered. Flowering continued into October 2019 for both variants, which, again, indicates a good nutrient supply. Additional liquid fertilization during pre-cultivation, therefore, has no influence on the higher flowering capacity of Heuchera micrantha ‘Palace Purple’.
Aster dumosus ‘Augenweide’ flowered in the first year from August 2018, which is in accordance with the typical flowering period for this perennial (Table 1). During the 2018 flowering period, 92% of the asters flowered on V1 and 87.5% of the asters flowered on V2. The peak of flowering was in October 2018 (Figure 9). In September and October 2019, 88% of the asters flowered on V1 and up to 83% flowered on V2. It can be concluded that the additional liquid fertilization during pre-cultivation influenced the flowering ability of Aster dumosus ‘Augenweide’ in 2018, but that the difference between V1 and V2 was minimal in 2019.
For Aster dumosus ‘Silberball’, 100% of the plants (Figure 10) flowered on both V1 and V2 in 2018 and 2019 and, thus, there were no differences between V1 and V2. The flowering period extended to October in 2018, and to September and October in 2019, which is in accordance with the usual flowering period (Table 1).
The test results on the number of flowers on the asters showed that the data were not homogeneously distributed.
Aster dumosus ‘Augenweide’ had between zero and 112 flowers per plant in October 2018 and between zero and 110 flowers per plant in October 2019 (Figure 11). Aster dumosus ‘Silberball’ had between four and 184 flowers per plant in October 2018 and between 70 and 350 flowers per plant in October 2019 (Figure 12). The average number of flowers of Aster dumosus ‘Augenweide’ differed significantly between V1 (30 flowers per plant) and V2 (five flowers per plant) in 2018. In 2019, there were no significant differences between V1 (38 flowers per plant) and V2 (34 flowers per plant). The average number of flowers of Aster dumosus ‘Silberball’ also differed significantly between V1 (100 flowers per plant) and V2 (35 flowers per plant) in October 2018. In 2019, the average number of flowers per plant continued to increase, but V1 (208 flowers per plant) and V2 (172 flowers per plant) did not differ significantly.
The liquid fertilizer had a positive influence on the flowering of the asters in 2018 during pre-cultivation, whereas no differences between V1 and V2 were observed after the vegetation mats were laid in the second year of the experiment. The fertilizing effect of the sheep’s wool is sufficient for flowering. Additional liquid fertilization during pre-cultivation, therefore, does not appear to be necessary regarding flowering capacity in the cultivation year after laying the vegetation mats.

3.5. Correlation between Dry Mass and Dry Matter of Asters

The above-ground dry mass of Aster dumosus ‘Augenweide’ and Aster dumosus ‘Silberball’ was significantly higher on V1 than on V2 in 2018 (Table 7). Aster dumosus ‘Augenweide’ achieved a dry mass of 18.72 g/plant on V1, 35% higher than on V2. Aster dumosus ‘Silberball’ achieved a dry mass of 12.51 g/plant on V1 (56% higher than on V2). In the following year 2019, strong growth in the biomass of the asters continued to be observed, with the biomass of Aster dumosus ‘Silberball’ being higher, this time, than that of Aster dumosus ‘Augenweide’ (Table 7). However, no significant differences were found between V1 and V2 in 2019. The increase in biomass is mainly due to the long-term fertilization effect of the sheep’s wool [43,46,47,48,49].
The dry matter of Aster dumosus ‘Augenweide’ and Aster dumosus ‘Silberball’ was significantly lower on V1 than on V2 in 2018 (Table 7), which suggests that there was a higher accumulation of minerals on V2. There was also a negative correlation between dry mass and dry matter (Table 8). In 2019, the dry matter of the asters increased further. No more significant differences were found between V1 and V2 in 2019.

3.6. Total Nitrogen Content of the Above-Ground Dry Mass of Asters

The total nitrogen content of the above-ground plant of Aster dumosus ‘Augenweide’ differed significantly between V1 (2.2%) and V2 (1.8%) in 2018. In 2019, Aster dumosus ‘Augenweide’ contained the same amount of total nitrogen on V2 (2.2%) as on V1 (2.1%) (Table 9) and there were no more significant differences between V1 and V2. The total nitrogen content of the above-ground plants of Aster dumosus ‘Silberball’ also differed significantly between V1 (1.7%) and V2 (1.4%) in 2018. In 2019, the total nitrogen content of the asters on V1 and V2 increased to 2.1%. There were no longer any significant differences between V1 and V2. It was shown that in the second year, the asters on V2 were able to accumulate just as much nitrogen as the asters on V1 (Table 9).

3.7. Correlations between N Content in the Above-Ground Dry Matter and Number of Flowers in Asters

In the experimental years 2018 and 2019, it was shown that there is a correlation between the nitrogen content of the above-ground biomass and the number of flowers on Aster dumosus ‘Augenweide’ (Figure 13 and Figure 14 and Table 10) and Aster dumosus ‘Silberball’ (Figure 15 and Figure 16 and Table 10).
The more nitrogen was taken up by the plant, the more flowers were formed. This shows that the higher the nitrogen uptake of the plant, the more flowers can be formed. This is due to the good fertilizing effect of the sheep’s wool, with a relatively high nitrogen content, which corresponds to the data from Böhme et al. [43]. How long the fertilizing effect of the sheep’s wool-coir-vegetation mats lasts would have to be investigated in more detail in a further trial. However, due to the thick-layered fiber structure of the vegetation mat, it can be assumed that biodegradation is much slower than with pressed sheep’s wool pellets. It is also conceivable that the vegetation mats could also be used for green roofs.

3.8. Coverage of Perennials

The coverage of perennials on the vegetation mats at the end of the first experimental year (11 October 2018) was 65% on V1 and 50% on V2 (Figure 17). Both vegetation mats were saleable after four months of pre-cultivation in October 2018, as coverage was 50% or above [50]. The plant coverage on the vegetation mats decreased from 10 October 2018, on V1 and V2, due to the natural retraction of the perennials in winter.
When the vegetation mats were laid in April 2019, the coverage of the perennials was 46% on V1 and 30% on V2 and differed significantly. During cultivation in 2019, the coverage on V2 increased more than on V1 (Figure 17). In June 2019, a coverage of 71% was already achieved on V2 compared to 84% on V1. In September and October 2019, no significant differences were found between V1 and V2 in terms of plant cover, which achieved almost 100% (Figure 1b). Here, too, it was shown that liquid fertilization during pre-cultivation is only advantageous in the first year of cultivation and that the fertilizing effect of the sheep’s wool is sufficient for complete plant coverage in the second year.

4. Conclusions

The results of this study show that liquid fertilization during the pre-cultivation of sheep’s wool–coir–vegetation mats does not affect the overall impression of the perennial mixture used in the first and second years.
In terms of plant height, two out of eight plant species benefited from the additional fertilization, but this does not speak in favor of an additional application of liquid fertilizer. An increased flowering ability of the perennials as a function of the additional liquid fertilizer was observed in perennials with a high nutrient requirement, such as asters in the first year of the trial. This was also reflected in a higher dry mass. Nevertheless, the vegetation mats that were not fertilized also looked attractive.
The saleability of the vegetation mats, regarding the minimum coverage of perennials of 50%, was achieved in both variants after pre-cultivation. That allows one to conclude that liquid fertilization is not necessary during pre-cultivation. However, it would be worth considering reducing the number of plants per m2 to give the perennials more space to spread out.
The conclusion is, due to the natural fertilizing effect of the sheep’s wool fibers in the vegetation mats, the perennials can be pre-cultivated in a sustainable and environmentally friendly way. During the completion care and maintenance care after the vegetation mats with perennials have been laid, there is also no need for additional fertilization, as sufficient nitrogen is still available. This allows savings both in terms of fertilizer use and staff costs. It is also environmentally friendly to use organic rather than mineral fertilizers, as there is less wash-out effect of the fertilizer.
Another advantage of using sheep’s wool in vegetation mats is that sheep’s wool is available in sufficient quantities worldwide and can be used regionally in vegetation mats, which is environmentally friendly and sustainable. The results will be important for horticulture regarding the use of sheep’s wool in vegetation mats and for the sheep industry worldwide.

Author Contributions

Conceptualization, S.H.; Methodology, S.H.; Formal analysis, S.H.; Investigation, S.H., V.M., and A.H.; Writing—original draft, S.H.; Project administration, S.H.; Supervision, H.G.; Writing—review and editing, H.G. All authors have read and agreed to the published version of the manuscript.

Funding

This project was funded by the Berlin Program for Sustainable Development (BENE) as well as by the European Regional Development Fund and the State of Berlin. (Funding code 1171-B5-O, project duration: 01/2018 to 06/2023). The article processing charge was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—491192747 and the Open Access Publication Fund of Humboldt-Universität zu Berlin.

Data Availability Statement

Data are contained within the article.

Acknowledgments

We would like to thank Sigrun Witt and Stephan Block from the Division Teaching and Research Station Greenhouse Area for their technical support during the experiments. We would like also thank Jan Häbler, Olga Gorbachevskaya, and Steffi Tschuikowa from the IASP, who supported us with her knowledge and support during the experiments, in statistical analyses and chemical analyses.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Experimental arrangement of perennial mats: (a) start of pre-cultivation with planted young plants (July 2018) and (b) end of the investigation period with a complete vegetation coverage (October 2019).
Figure 1. Experimental arrangement of perennial mats: (a) start of pre-cultivation with planted young plants (July 2018) and (b) end of the investigation period with a complete vegetation coverage (October 2019).
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Figure 2. Influence of liquid fertilizer application in 2018 on the percentage distribution of overall impression on V1 and V2 (a) at last assessment date in 2018 (11 October 2018) and (b) at last assessment date in 2019 (9 October 2019). Score: 1 = plant failure, 3 = sufficient, 5 = satisfactory, 7 = good, and 9 = very good.
Figure 2. Influence of liquid fertilizer application in 2018 on the percentage distribution of overall impression on V1 and V2 (a) at last assessment date in 2018 (11 October 2018) and (b) at last assessment date in 2019 (9 October 2019). Score: 1 = plant failure, 3 = sufficient, 5 = satisfactory, 7 = good, and 9 = very good.
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Figure 3. Influence of liquid fertilizer application in 2018 on the flowers of Achillea clypeolata ‘Moonshine’ in 2019. V1: n = 17; V2: n = 16. n = number of plants.
Figure 3. Influence of liquid fertilizer application in 2018 on the flowers of Achillea clypeolata ‘Moonshine’ in 2019. V1: n = 17; V2: n = 16. n = number of plants.
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Figure 4. Influence of liquid fertilizer application in 2018 on the flowers of Anemone sylvestris in 2019. V1: n = 23; V2: n = 23. n = number of plants.
Figure 4. Influence of liquid fertilizer application in 2018 on the flowers of Anemone sylvestris in 2019. V1: n = 23; V2: n = 23. n = number of plants.
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Figure 5. Influence of liquid fertilizer application in 2018 on the flowers of Buphthalmum salicifolium in 2019. V1: n = 19; V2: n = 18. n = number of plants.
Figure 5. Influence of liquid fertilizer application in 2018 on the flowers of Buphthalmum salicifolium in 2019. V1: n = 19; V2: n = 18. n = number of plants.
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Figure 6. Influence of liquid fertilizer application in 2018 on the flowers of Festuca glauca in 2019. V1: n = 24; V2: n = 24. n = number of plants.
Figure 6. Influence of liquid fertilizer application in 2018 on the flowers of Festuca glauca in 2019. V1: n = 24; V2: n = 24. n = number of plants.
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Figure 7. Influence of liquid fertilizer application in 2018 on the flowers of Fragaria vesca in 2018 and 2019. V1: n = 24; V2: n = 24. n = number of plants.
Figure 7. Influence of liquid fertilizer application in 2018 on the flowers of Fragaria vesca in 2018 and 2019. V1: n = 24; V2: n = 24. n = number of plants.
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Figure 8. Influence of liquid fertilizer application in 2018 on the flowers of Heuchera micrantha ‘Palace Purple’ in 2018 and 2019. V1: n = 24; V2: n = 24. n = number of plants.
Figure 8. Influence of liquid fertilizer application in 2018 on the flowers of Heuchera micrantha ‘Palace Purple’ in 2018 and 2019. V1: n = 24; V2: n = 24. n = number of plants.
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Figure 9. Influence of liquid fertilizer application in 2018 on the flowers of Aster dumosus ‘Augenweide’ in 2018 and 2019. V1: n = 24; V2: n = 24. n = number of plants.
Figure 9. Influence of liquid fertilizer application in 2018 on the flowers of Aster dumosus ‘Augenweide’ in 2018 and 2019. V1: n = 24; V2: n = 24. n = number of plants.
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Figure 10. Influence of liquid fertilizer application in 2018 on the flowers of Aster dumosus ‘Silberball’ in 2018 and 2019. V1: n = 24; V2: n = 24. n = number of plants.
Figure 10. Influence of liquid fertilizer application in 2018 on the flowers of Aster dumosus ‘Silberball’ in 2018 and 2019. V1: n = 24; V2: n = 24. n = number of plants.
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Figure 11. Box plot comparison of influence of liquid fertilizer application in 2018 on the number of flowers per plant of Aster dumosus ‘Augenweide’ at last assessment date in 2018 (11 October 2018) and at last assessment date in 2019 (9 October 2019). V1: n = 24; V2: n = 24. n = number of plants.
Figure 11. Box plot comparison of influence of liquid fertilizer application in 2018 on the number of flowers per plant of Aster dumosus ‘Augenweide’ at last assessment date in 2018 (11 October 2018) and at last assessment date in 2019 (9 October 2019). V1: n = 24; V2: n = 24. n = number of plants.
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Figure 12. Box plot comparison of influence of liquid fertilizer application in 2018 on the number of flowers per plant of Aster dumosus ‘Silberball’ at last assessment date in 2018 (11 October 2018) and at last assessment date in 2019 (9 October 2019). V1: n = 24; V2: n = 24. n = number of plants.
Figure 12. Box plot comparison of influence of liquid fertilizer application in 2018 on the number of flowers per plant of Aster dumosus ‘Silberball’ at last assessment date in 2018 (11 October 2018) and at last assessment date in 2019 (9 October 2019). V1: n = 24; V2: n = 24. n = number of plants.
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Figure 13. Relationships between N content and number of flowers per plant of Aster dumosus ‘Augenweide’ on V1 and V2 (n = 48) in 2018. n= number of plants.
Figure 13. Relationships between N content and number of flowers per plant of Aster dumosus ‘Augenweide’ on V1 and V2 (n = 48) in 2018. n= number of plants.
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Figure 14. Relationships between N content and number of flowers per plant of Aster dumosus ‘Augenweide’ on V1 and V2 (n = 48) in 2019. n = number of plants.
Figure 14. Relationships between N content and number of flowers per plant of Aster dumosus ‘Augenweide’ on V1 and V2 (n = 48) in 2019. n = number of plants.
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Figure 15. Relationships between N content and number of flowers per plant of Aster dumosus ‘Silberball’ on V1 and V2 (n = 48) in 2018. n = number of plants.
Figure 15. Relationships between N content and number of flowers per plant of Aster dumosus ‘Silberball’ on V1 and V2 (n = 48) in 2018. n = number of plants.
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Figure 16. Relationships between N content and number of flowers per plant of Aster dumosus ‘Silberball’ on V1 and V2 (n = 48) in 2019. n = number of plants.
Figure 16. Relationships between N content and number of flowers per plant of Aster dumosus ‘Silberball’ on V1 and V2 (n = 48) in 2019. n = number of plants.
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Figure 17. Development of the average coverage of perennials on the two vegetation mat variants V1 and V2 after pre-cultivation (2018) and after final laying on site (2019).
Figure 17. Development of the average coverage of perennials on the two vegetation mat variants V1 and V2 after pre-cultivation (2018) and after final laying on site (2019).
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Table 1. Overview of the selected perennials and requirements, information based on [33].
Table 1. Overview of the selected perennials and requirements, information based on [33].
Botanical NamePlant Height (m)Flowering TimeNutrient RequirementsSpecial
Requirements
Achillea clypeolata ‘Moonshine’0.40–0.60June–Julyhigh, nutritious, medium, normal, balancedheat-loving
Anemone sylvestris L.0.20–0.30May–Junemedium, normal, balancedadaptable
Aster dumosus ‘Augenweide’0.25–0.30August–Octoberhigh, nutritiousadaptable
Aster dumosus ‘Silberball’0.30–0.40September–Octoberhigh, nutritiousadaptable
Buphthalmum salicifolium L.0.40–0.50June–Augustmedium, normal, balanced to low, low in nutrientsadaptable
Festuca glauca Vill.0.20–0.30June–Julylow, low in nutrientsheat-loving
Fragaria vesca L.0.15–0.20May–Junehigh, nutritiousadaptable
Heuchera micrantha ‘Palace Purple’0.40–0.50July–Augusthigh, nutritious to medium, normal, balancedadaptable
Table 2. Composition of vegetation mats and their weight proportion (±SE) and calculated nitrogen content (±SE) of the fibers (air-dry) in used vegetation mats at the beginning of pre-cultivation.
Table 2. Composition of vegetation mats and their weight proportion (±SE) and calculated nitrogen content (±SE) of the fibers (air-dry) in used vegetation mats at the beginning of pre-cultivation.
Mat VariantTotal Weight of Mixed Fibers (kg/m2)Total N of Mixed Fibers (g/m2)Total N of Additional Liquid Fertilizer (g/m2)Total N of Mixed Fibers and Additional Liquid Fertilizer (g/m2)
V1: 50% sheep’s wool and 50% coir
Treatment with liquid fertilizer
during pre-cultivation		4.478 ± 0.107241.8 ± 5.88.7 ± 0.0250.5 ± 5.8
V2: 50% sheep’s wool and 50% coir
Treatment without liquid fertilizer
during pre-cultivation		4.547 ± 0.070245.5 ± 3.80.0 ± 0.0245.5 ± 3.8
Table 3. Influence of liquid fertilizer application in 2018 on the overall impression of all perennials on V1 and V2 during pre-cultivation in 2018 determined over all 7 assessment dates.
Table 3. Influence of liquid fertilizer application in 2018 on the overall impression of all perennials on V1 and V2 during pre-cultivation in 2018 determined over all 7 assessment dates.
Botanical NameScore [a] (Median) of V1 Score [a] (Median) of V2
Achillea clypeolata ‘Moonshine’77
Anemone sylvestris L.77
Aster dumosus ‘Augenweide’77
Aster dumosus ‘Silberball’97
Buphthalmum salicifolium L.53
Festuca glauca Vill.97
Fragaria vesca L.77
Heuchera micrantha ‘Palace Purple’77
All plants (Median)77
[a] Score: 3 = sufficient, 5 = satisfactory, 7 = good, and 9 = very good.
Table 4. Influence of liquid fertilizer application in 2018 on the overall impression of all perennials on V1 and V2 after laying in 2019 determined over all 7 assessment dates.
Table 4. Influence of liquid fertilizer application in 2018 on the overall impression of all perennials on V1 and V2 after laying in 2019 determined over all 7 assessment dates.
Botanical NameScore [a] (Median) of V1Score [a] (Median) of V2
Achillea clypeolata ‘Moonshine’55
Anemone sylvestris L.95
Aster dumosus ‘Augenweide’77
Aster dumosus ‘Silberball’99
Buphthalmum salicifolium L.77
Festuca glauca Vill.75
Fragaria vesca L.77
Heuchera micrantha ‘Palace Purple’76
All plants (Median)77
[a] Score: 5 = satisfactory, 6 = satisfactory to good, 7 = good, and 9 = very good.
Table 5. Influence of liquid fertilizer application in 2018 on the average plant height (±SE) of all perennials (n = 24) on V1 and V2 at last assessment date in 2018 (11 October 2018).
Table 5. Influence of liquid fertilizer application in 2018 on the average plant height (±SE) of all perennials (n = 24) on V1 and V2 at last assessment date in 2018 (11 October 2018).
Botanical NameAverage Plant Height (cm) of V1Average Plant Height (cm) of V2
Achillea clypeolata ‘Moonshine’20.3 ± 1.0 a (n = 19)16.2 ± 0.5 b (n = 17)
Anemone sylvestris L.9.0 ± 1.1 a7.2 ± 1.0 a
Aster dumosus ‘Augenweide’20.6 ± 0.9 a20.5 ± 0.8 a
Aster dumosus ‘Silberball’33.4 ± 0.5 a33.2 ± 0.8 a
Buphthalmum salicifolium L.7.7 ± 1.8 (n = 16) a5.2 ± 0.8 (n = 21) a
Festuca glauca Vill.16.5 ± 0.7 a12.6 ± 0.6 b
Fragaria vesca L.13.4 ± 0.4 a14.0 ± 0.6 a
Heuchera micrantha ‘Palace Purple’28.4 ± 1.0 a27.2 ± 1.0 a
n = number of plants. Statistically significant differences are indicated by different letters and refer to only one plant species on V1 or V2 (two-sided Tukey’s-test, p ≤ 0.05).
Table 6. Influence of liquid fertilizer application in 2018 on the average plant height (±SE) of all perennials (n = 24) on V1 and V2 at last assessment date in 2019 (9 October 2019).
Table 6. Influence of liquid fertilizer application in 2018 on the average plant height (±SE) of all perennials (n = 24) on V1 and V2 at last assessment date in 2019 (9 October 2019).
Botanical NameAverage Plant Height (cm) of V1Average Plant Height (cm) of V2
Achillea clypeolata ‘Moonshine’37.1 ± 2.4 a (n = 17)42.0 ± 2.7 a (n = 16)
Anemone sylvestris L.30.5 ± 1.4 a (n = 23)23.7 ± 1.4 b (n = 23)
Aster dumosus ‘Augenweide’33.7 ± 1.7 a29.5 ± 1.4 a
Aster dumosus ‘Silberball’56.8 ± 0.9 a55.0 ± 0.8 a
Buphthalmum salicifolium L.46.2 ± 3.2 a (n = 19)45.4 ± 2.7 a (n = 18)
Festuca glauca Vill.46.8 ± 1.2 a41.7 ± 1.2 b (n = 23)
Fragaria vesca L.n.d.n.d.
Heuchera micrantha ‘Palace Purple’23.9 ± 1.4 a22.2 ± 1.0 a
n = number of plants. n.d. = not determined. Statistically significant differences are indicated by different letters and refer to only one plant species on V1 or V2 (two-sided Tukey’s-test, p ≤ 0.05).
Table 7. Average above-ground dry mass and dry matter per plant (±SE) of Aster dumosus ‘Augenweide’ (n = 24) and Aster dumosus ‘Silberball’ (n = 24) in 2018 and 2019.
Table 7. Average above-ground dry mass and dry matter per plant (±SE) of Aster dumosus ‘Augenweide’ (n = 24) and Aster dumosus ‘Silberball’ (n = 24) in 2018 and 2019.
Mat VariantDry Mass per Plant (g) of V1Dry Mass per Plant (g) of V2Dry Matter
per Plant (%) of V1		Dry Matter
per Plant (%) of V2
Aster dumosus ‘Augenweide’ (11 October 2018)18.72 ± 1.33 a13.86 ± 1.11 b25.2 ± 0.8 a28.4 ± 0.8 b
Aster dumosus ‘Augenweide’ (9 October 2019)48.05 ± 8.32 a34.93 ± 7.16 a42.4 ± 2.5 a45.2 ± 2.7 a
Aster dumosus ‘Silberball’ (11 October 2018)12.51 ± 0.77 a8.04 ± 0.64 b35.2 ± 0.7 a38.4 ± 0.7 b
Aster dumosus ‘Silberball’ (9 October 2019)94.97 ± 4.81 a87.25 ± 6.96 a49.9 ± 1.1 a50.5 ± 1.3 a
n = number of plants. Statistically significant differences are indicated by different letters and refer to only one plant species on V1 or V2 (two-sided Tukey’s-test, p ≤ 0.05).
Table 8. Pearson correlation between above-ground dry mass and dry matter per plant of Aster dumosus ‘Augenweide’and Aster dumosus ‘Silberball’ in 2018 and 2019.
Table 8. Pearson correlation between above-ground dry mass and dry matter per plant of Aster dumosus ‘Augenweide’and Aster dumosus ‘Silberball’ in 2018 and 2019.
20182019
Aster dumosus ‘Augenweide’
Sig. (2-tailed)		−0.426 **
0.003		−0.502 **
<0.001
Aster dumosus ‘Silberball’
Sig. (2-tailed)		−0.590 **
<0.001		-
** The correlation is significant on a level of 0.01 (2-tailed).
Table 9. Average total nitrogen content per plant (±SE) of Aster dumosus ‘Augenweide’ (n = 24) and Aster dumosus ‘Silberball’ (n = 24) on V1 and V2 at last assessment dates in 2018 and 2019.
Table 9. Average total nitrogen content per plant (±SE) of Aster dumosus ‘Augenweide’ (n = 24) and Aster dumosus ‘Silberball’ (n = 24) on V1 and V2 at last assessment dates in 2018 and 2019.
PerennialAverage Total N Content per Plant (%) of V1Average Total N Content per Plant (%) of V2
Aster dumosus ‘Augenweide’ (11 October 18)2.2 ± 0.0 a1.8 ± 0.0 b
Aster dumosus ‘Augenweide’ (9 October 19)2.2 ± 0.0 a2.1 ± 0.1 a
Aster dumosus ‘Silberball’ (11 October 18)1.7 ± 0.0 a1.4 ± 0.0 b
Aster dumosus ‘Silberball’ (9 October 19)2.1 ± 0.0 a2.1 ± 0.0 a
n = number of plants. Statistically significant differences are indicated by different letters and refer to only one plant species on V1 or V2 (two-sided Tukey’s-test, p ≤ 0.05).
Table 10. Pearson-correlation between N content and number of flowers per plant of Aster dumosus ‘Augenweide’ and Aster dumosus ‘Silberball’ on V1 and V2 in 2018 and 2019 (n = 48).
Table 10. Pearson-correlation between N content and number of flowers per plant of Aster dumosus ‘Augenweide’ and Aster dumosus ‘Silberball’ on V1 and V2 in 2018 and 2019 (n = 48).
20182019
Aster dumosus ‘Augenweide’
Sig. (2-tailed)		0.755 **
<0.001		0.864 **
<0.001
Aster dumosus ‘Silberball’
Sig. (2-tailed)		0.778 **
<0.001		0.516 **
<0.001
** The correlation is significant on a level of 0.01 (2-tailed).
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Herfort, S.; Maß, V.; Hüneburg, A.; Grüneberg, H. Influence of Mineral Liquid Fertilization on the Plant Growth of Perennials on Sheep’s Wool–Coir–Vegetation Mats. Horticulturae 2024, 10, 773. https://doi.org/10.3390/horticulturae10080773

AMA Style

Herfort S, Maß V, Hüneburg A, Grüneberg H. Influence of Mineral Liquid Fertilization on the Plant Growth of Perennials on Sheep’s Wool–Coir–Vegetation Mats. Horticulturae. 2024; 10(8):773. https://doi.org/10.3390/horticulturae10080773

Chicago/Turabian Style

Herfort, Susanne, Virginia Maß, Amelie Hüneburg, and Heiner Grüneberg. 2024. "Influence of Mineral Liquid Fertilization on the Plant Growth of Perennials on Sheep’s Wool–Coir–Vegetation Mats" Horticulturae 10, no. 8: 773. https://doi.org/10.3390/horticulturae10080773

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