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There are two basic issues concerning basic and supplemental fertilization of forest stands. The first one concerns nutrition of nursery seedlings in and/or outside containers while the second one stock fertilization of seedlings after their replantation to target locality and supplemental fertilizing of young trees.


A lot of various types of stock fertilizers with an extended period of efficiency have been developed for this purpose. Perhaps the best known of them is the pelleted fertilizer Osmocote which is used throughout Europe, first of all in ornamental plant nurseries. Application of such fertilizers seems to be important especially in the field of establishment of permanent stands because it provides a continuous supply of nutrients to plants throughout the most critical period of their existence, i.e. after replanting, during the period of rooting and in the first stage of their growth and development. This critical period may last either for several months (e.g. for herbs) or even for several years (in case of woody species) and depends above all on climatic factors occurring in the given period of time. It is also obvious that after their replantation in the target locality it is mostly impossible to provide the plants with a similar care as in the period of pre-planting.


Tebletted, long-term soluble feritlizers of the series SILVAMIX® represent a prospective product of Czech provenience. At our university, these fertilizers have been tested and used since the year 1991. Ornamental woody species grown in containers were investigated in two stages. It can be said that plants grown in this way are more susceptible to fluctuations of major environmental factors (i.e. temperature, irrigation and nutrition) than those cultivated on seed beds. However, the obtained results were very favourable regardless to this fact. During the first stage of our experiments, long-term dressing effects of SILVAMIX? FORTE (N - 17.5%; P2O5 - 17.5%; K20 - 10.5%; MgO - 9.0%) and SILVAMIX® MG (N - 8.0%; P2O5 - 12.0%; K20 - 5.0%; MgO - 15.0%) fertilizers (manufacturer ECOLAB ZNOJMO Ltd., Czech Republic) were tested using ornamental woody species mentioned below.


Experiments with ornamental plants were established using one-year-old cuttings and seedlings of the following deciduous and evergreen woody species: Cotoneaster dammeri ´Skogholm´, Berberis thunbergii and Potentilla fruticosa ´Snowflake´. After planting into containers, fertilizers in the dose of 1 tablet (i.e. 10 g) per litre of substrate were applied either to roots level or on the soil surface in the container. Control plants were fertilized in the course of growing season using a common agricultural fertilizer Cererit Z (N - 10.0%; P2O5 - 9.0%; K20 - 14.0%; MgO - 1.3% ; manufacturer Synthesia a.s. Pardubice, Czech Republic). Experimental plants were grown in containers placed on a black plastic foil. For irrigation, a classical irrigation system PUK was used. Experiments were carried out within the framework of a routine operation of ornamental nursery in the course of two growing seasons. A random checking carried out to the end of the third year of cultivation revealed well visible remnants of disintegrated tablets in the substrate.


Table 1a: Average annual increment - Cotoneaster dammeri "Skogholm"

Growing season SILVAMIX® MG, surface application SILVAMIX® MG, application to the roots level SILVAMIX® Forte, application to the roots level Control CERERIT Z
  cm % cm % cm % cm %
1 17.8 172.8 21.9 212.6 17.6 170.9 10.3 100.0
2 22.7 89.7 21.6 85.4 16.0 63.2 25.3 100.0
1 + 2 40.5 113.1 43.5 121.5 33.6 93.9 35.8 100.0


Table 1b: Average annual increment - Berberis thunbergii

Growing season SILVAMIX® MG, surface application SILVAMIX® MG, application to the roots level SILVAMIX® Forte, application to the roots level Control CERERIT Z
  cm % cm % cm % cm %
1 49.0 242.6 36.2 179.2 25.5 126.2 20.2 100.0
2 15.9 93.5 18.8 110.6 15.7 92.4 17.0 100.0
1 + 2 64.9 174.5 55.0 147.9 41.2 110.8 37.2 100.0


Table 1c: Average annual increment - Potentilla fructicosa "Snowflake"

Growing season SILVAMIX® MG, surface application SILVAMIX® MG, application to the roots level SILVAMIX® Forte, application to the roots level Control CERERIT Z
  cm % cm % cm % cm %
1 24.5 140.8 24.4 140.2 21.8 125.3 17.4 100.0
2 12.0 85.1 14.9 105.7 16.6 117.7 14.1 100.0
1 + 2 36.5 115.9 39.3 124.8 38.4 121.9 31.5 100.0


The evaluation of results of our two-year experiments revealed that after the application of SILVAMIX® fertilizers the annual increments of experimental plants were statistically different. In the first year, these annual increments were significantly higher in all cases than those recorded in the following year. Although in the second year the annual increments were slightly lower, it was possible to demonstrate a generally very positive effect of applied fertilizers on the long-term growth of container cultures. It is also necessary to remember that control plants were fertilized with CERERIT Z repeatedly in both years of the experiment while the experimental ones only once, i.e. after re-planting into containers. However, as compared with repeatedly applied agricultural fertilizer CERERIT Z with rapidly released nutrients, the expected bi-annual effect of SILVAMIX® fertilizers could be demonstrated very easily and the overall increase ranged, in dependence on plant species, chemical composition of fertilizers, their texture and method of application, from 10 to 75%. This means that the efficiency of fertilizers releasing nutrients slowly was significantly better in woody species growing for several seasons than that of common, rapidly soluble products and that the optimum results could be obtained by means of a proper selection of nutrient composition of fertilizer (i.e. SILVAMIX® FORTE, SILVAMIX® MG), method of application (i.e. on the soil surface, to roots level or into the substrate) and texture (i.e. in the form of a powder or in tablets). This can be seen in Tabs 2a - 2c, 3a and 3b.


When growing ornamental plants in containers it is always necessary to adapt both the amount and the form of supplied nutrients to plant requirements and to physical properties of substrates used under conditions of intensive daily irrigation. It can be said that from this point of view the obtained results are very valuable and that they will be definitely appreciated by every experienced nurseryman.


When analyzing all stress factors influencing the growth of plants cultivated in containers it is possible to expect that, with regard to results of an analysis of overall bi-annual increments of wood species mentioned above, their cultivation on seed beds should give undoubtedly better results and that the effect of SILVAMIX® fertilizers on these plants would be even better than in our experiments. Besides, these experiments also corroborated our earlier observations that when growing plants in containers, i. e. outside the seed beds, it is appropriate to think about a supplementary dressing of woody species in the spring season of the second year (i. e. after the application of tablets) with fertilizers containing easily available nitrogen; however, it is necessary to take into account climatic conditions of the first year of growing (i.e. precipitation and temperatures), irrigation intensity (because of danger of substrate elution) and nutritional requirements of plants. This recommendation concerns above all ornamental woody species with higher nutritional requirements.


A very good development of roots of experimental plants dressed with SILVAMIX? fertilizers represents a significant advantage because it is important for their subsequent growth and development on the target site. In case of application of tabletted fertilizers it was also possible to demonstrate a significant role of chemotropism of plants in the mechanism of their nutrition, i.e. the capacity to change the direction of root growth in dependence on the chemical composition of soil. In practice this means that new roots encircle the tablet with a dense network of hairy roots and thus create good predispositions for the maximum utilization of nutrients. When using tablets, the osmotic values of soil substrate are several times lower than in case of application of the same dose of complex, water-soluble and chloride-free fertilizers so that it is possible to apply them even to more sensitive plants.


The data presented above also indicate that a targeted, focal application of tabletted SILVAMIX? fertilizers can result in a cost reduction in the course of growing season. When using soluble mineral fertilizers, the basic (i.e. stock) dose is mixed with substrate at the moment of planting and the necessary nutrients are replenished by means of supplementary dressing in the course of growing season. However, these stock and slowly soluble fertilizers enable to simplify the system of plant nutrition. Their application ensures a better use of nutrients, their lower losses due to retrogradation and, especially, wash-off into groundwater, and, last but not least, better economic results. Until now, a practical experience with application of fertilizers in ornamental and forest nurseries indicates that an undoubtedly high quality of these products is further increased due to a possibility to apply them as top dressing but without any danger of leaf burning (in nurseries, a supplementary dressing of young plants with solid fertilizers belongs to the most demanding working operations especially because of an acute danger of burning of plants). This was completely proved during the second stage of our experiments.


In the second stage of our experiments with SILVAMIX? fertilizers, attention was paid to testing of their effects on other genera of woody plants on the one hand and to the evaluation of efficiency of their application in the form of powders. This was done due to requirements of horticultural practice because it was not always possible to apply tablets under conditions of normal operation. Depending on the equipment, a powder can be mixed with the substrate before planting and the possibility of its application as top dressing is also rather interesting.


For these experiments plants grown in containers were used. Seedlings were planted into containers with the volume of 1 litre and placed on a shaded area. SILVAMIX® FORTE in the dose of 5 g.l-1 was used as the tested fertilizer. It was applied during the planting in the form of tablets and/or a powder. For experiments, both rooted cuttings of Ligustrum vulgare "Atrovirens" and seedlings of Picea omorika were used (in 1995, seedlings from the forest nursery 0/2 were used while in 1996 the experimental seedlings were older by one year) . In the course of growing season, both controls and experimental plants were routinely treated and irrigated. In controls, CERERIT Z was again used for the fertilization. No phytotoxic damage of plants was observed after the application of fertilizers in any variant of the experiment.


Results of one-year experiments carried out in 1995 and 1996 are presented in Tabs 2a - 2c, 3a and 3b. Experiments were established in spring and evaluated after the end of growing season. Methodology and sites of all experiments were identical in both years and the treatment as well. As shown in Tabs 2 and 3, the second stage corroborated results obtained earlier. For our practice, the most important observation represents the fact that fertilizers of the SILVAMIX® product line can be applied in different forms (i.e. as tablets or in the form of a powder) without any differences in their efficiency. Their application in the powdered form provides new possibilities of supplementary dressing not only in nurseries but also on permanent sites. From the economic point of view, such an application is advantageous in case of their extensive application (i.e. as supplementary dressing of bare land, in closed stands and as admixtures into growing substrates) while tablets enable the maximum economy in case of individual application (provided that the principles of dressing are observed and that all workers are fully responsible and reliable and that they respect recommended doses and methods). The possibility of application of powdered form using spreading machines without any greater danger of chemical damage of aboveground parts of plants represents another enumerable advantage of this method.


Table 2a: The average height of plants - Ligustrum vulgare "Atrovirens"

Form of fertilizer Average height of plants - annual experiments
  cm % cm %
Control 11.85 100.00 13.48 100.00
Tablets 19.27 162.60 27.97 207.50
Powder 17.58 148.35 24.33 180.50


Table 2b The average number of lateral annual shoots - Ligustrum vulgare "Atrovirens"

Form of fertilizer Average number of lateral annual shoots - annual experiments
  cm % cm %
Control 6.42 100.00 6.10 100.00
Tablets 7.06 109.97 6.30 103.30
Powder 6.34 98.75 5.60 91.80


Tab. 2c: The average increments in the course of growing season - Ligustrum vulgare "Atrovirens"

Form of fertilizer Average increment in the course of growing
season - annual experiments
  cm % cm %
Control 27.35 100.00 30.00 100.00
Tablets 50.86 185.96 80.75 269.20
Powder 47.09 172.18 62.44 208.10


Table 3a: Average height of plants - Picea omorika

Form of fertilizer Average height of plants - annual experiments
  cm % cm %
Control 13.35 100.00 24.44 100.00
Tablets 14.06 105.32 22.30 91.20
Powder 14.25 106.74 23.11 94.60


Table 3b: Average length of the terminal increment - Picea omorika

Form of fertilizer Average length of the terminal
increment - annual experiments
  cm % cm %
Control 3.30 100.00 3.23 100.00
Tablets 3.50 106.06 3.48 107.70
Powder 3.75 113.64 3.12 96.60



  1. A general evaluation of our experiments showed that the ecological fertilizer SILVAMIX? FORTE was comparable with the top foreign products. However, its price is much more acceptable. These experiments demonstrated a long-term optimum effect of this product on woody species and an equal quality and efficiency of its tabletted and powdered forms. When comparing the effects of its application on the soil surface and into the substrate no marked differences were found out. The method of application is dependent on the technology used and needs of the user.

  2. No phytotoxic damage of experimental woody species was observed immediately after the application of fertilizers or in the course of our experiments. Basing on our experience with the application of other tabletted fertilizers it is possible to conclude that these fertilizers show a very well solved binding of individual elements combined with their gradual release into the substrate; this is important above all in case of nitrogen because there is a danger of "burning? of roots due to their direct contact with fertilizer or due to its rapid release as well as a danger of overdosage with nitrogen within the first year after its application (because of a bad ripening of wood and a subsequent damage during the winter season) and/or due to a nitrogen deficiency caused by wash-off of nutrients in the year to follow. An optimum plant nutrition, as ensured by SILVAMIX® fertilizers in combination with substances affecting positively the water regime in soil or in substrate (e.g. by hydroabsorbents TerraCotem or Gefa Fabrosan) can help to a more rational use of applied fertilizers by woody species. Nevertheless, it is recommended to pay attention to a preventive additional dressing with an easily available form of nitrogen at the beginning of the second year of cultivation, especially for species with higher requirements of nutrients, in case of cultivation of woody species under conditions of their growing outside the seed bed (i.e. intensive irrigation, very permeably substrate, frequent stress situations due to fluctuations of abiotic factors).

  3. Within the period of seven-year experiments, an overall positive effect of applied fertilizers on the development of plants under study was demonstrated. They showed a positive effect on the dynamics of growth annual shoots. In spite of a more intensive growth of annual shoots no greater damage of plants than in control was recorded due to a bad ripening of annual shoots. Experimental plants were more resistant to stress conditions, especially to fluctuation of temperature and humidity. As compared with controls, lower loses in the course of cultivation were recorded and the root system was denser, of better quality and with a better degree of rooting. This is a very important observation because such plants are more predisposed to overcome the shock caused by replanting to the permanent site and they are a warranty of good rooting and growth.

Lednice, 16 February 1998