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The forest economy of the North Bohemian region has for long been under direct adverse influence of emissions from industrial enterprises, situated both in this country and abroad. Mountainous parts of the Krusne hory (Ore Mountains) are destroyed, mainly by sulhur dioxide immissions (but by others as well), the situation is similar in Jizerske hory region and the negative impacts can also be seen in the Luzicke hory area. The essential growth medium is damaged to such extent that any renewing of a forest in said regions is not possible without an adjustment of the soil conditions. The prerequisite to the succcess of the afforestation is to improve the soil fertility in such a way that the state of soil should be adjusted at acceptable conditions enabling the growth of newly established cultures.


One way of how to achieve such a state is liming as a long-term control intervention for pH adjustment, which, however, cannot solve the critical disorders in plant nutrition brought about by immissions. Fertilization is an important operation securing the nutrition of cultures, whose objective is to intensify growth and to increase the vitality and resistance to the whole set of stress factors that are cropping up nowadays.


Analysis of soil samples from representative parts of the Ore Mountains have proved that due to the acidic fall-out the soil acidity is becoming markedly worse and, at the same time, the contents of calcium, phosphorus, potassium and magnesium have decreased to such a limit at which growth of the seedlings is no more possible.


Fertilizing as practised originally by means of convenctional fertilizers (e.g. with NPK-1) has but a shocking and short-term effect.


Based on ascertained facts and using the available knowledge on the nutrition of plants, the Research Institute of Inorganic Chemistry (RIIC) suggested the formulation of a fertilizer for long-term adjustment of the soil medium within direct reach of the root system  of a seedling, whereby the natural development of the root system would be guaranteed.


The composition of the fertilizer is given by the ratio  N : P : K : Mg = 2.12-1.74 : 1.36-1.12 : 2.82-2.36 : 0.2-0.3.


The method of  localized (pointed) application of this type of fertilizer (compacts in the form of tablets, weight 10 g each) has been chosen according to which a total dose of 40 g is given to each seedling. (Placed in four points along the perimeter of spread of the seedling in the vertices of a hypothetical square).  The dose is applied onto the soil surface above the rot system by simply putting the tablet down either unprotected or protected by a mulching cloth.


The expected and experimentally confirmed gradual and slow releasing of the nutrients is made possible by a proper selection of a suitable raw materials. The length of the period of action has been tested by filed experiments and these confirm the functionality of the tablets to be 2 - 3 years.


The manufacture of the discussed type fertilizer has been taken up by the ECOLAB ZNOJMO Ltd.,  (Czech Republic) who in cooperation with RIIC and the Management of the North-Bohemian State Forests developed the manufacturing process and secure the star-up production of fertilizer under the trade name SILVAMIX® especially for covering the requirements of the enterprise North-Bohemian Forests since 1989.


In order to obtain an objective evaluation of the effect achieved by using the tableted fertilizer SILVAMIX®  the branch Institute Forestry and Game Management of Res. Inst. at Zbraslav-Strnady was asked to carry out an overall evaluation of the trials established in the region of the greatest immission load affecting the forest soil - in the Ore Mountains.


For comparison´s sake two large-scale trials were established by the Janov forest enterprise - on the Hranicni cesta locality, forest range Nacetin and on the Cervena Jama locality, forest range Jezeri. In both these cases the least favourable situation was chosen - i.e. the heaviest immissions load in the "A" zone of exposure (active pH - 3.37, exchange pH - 2.77, supply of available nutrients: P2O5 - 57, K2O - 96, CaO - 170, MgO 55). The localities Cervena Jama and Hranicni cesta were exploited in 1982 followed by a large-area ground preparation (by bulldozing), machine planting of wrapped seedlings and by sowing of birch seeds on the mounds.


Before forestation (in 1983-4) both localities had been limed by micronized limestone (2.1 tonne/ha). Within the framework of the trial the seedlings on a part of the plots were protected against weed attack by mulching cloths and additionally fertilized by the tablets at 34 g/plant in the autumn 1984.


Every year after termination of the vegetation increase the increments on the trial plots were measured by the researchers - measurements of height and registering of the number of healthy and viable seedlings.


Since both the trial plots were included in the regular plan of forestation the perished seedlings were systematically replaced by new plants, which manifested itself by a certain not very significant distortion of the obtained results, which concerns mainly the D-group, the check plot.


The following trial plots were established:

Group Designation Method
A Protection by cloths Additional fertilization with tablets
B Protection by cloths No fertilization
C No protection Additional fertilization with tablets
D No protection No fertilization


The results of the investigations carried out over the period of 1984 - 1989 were subjected to statistical processing in order to obtain comparable data.


Results of investigations

The influence of the fertilizer tablets on the seedlings increment is demonstrated in Fig.1 - Yearly Increment in Groups. It can be seen in the diagram that the effect of fertilizing showed itself  by intensive growth in 1985 and particularly in 1986, when a maximum was attained. The increases, related to the initial state in the individual groups, were as follows:


A:     + 51.6%  (32 cm)
B:     + 46.3%  (25 cm)
C:     + 46.3%  (25 cm)
D:     + 17.5%  (  7 cm)


A degression in the increments occured in 1987 due to a period of prevailing drought on the one hand and because of the decrease in the disposable supply of nutrients on the other hand. The activity of growing was enlivened in the period 1988 - 89 after a large-scale maintenance liming with ground dolomitic limestone whereby the pH was adjusted at the optimum value of 3.5 (exchange), which affected favourably the condition of the soil supply of nutrients, both natural and residual from the tablets.


Fig.2 - "Year by Year Increase as Compared with Untreated Culture" documents explicitly the importance of protection and treatment of the cultures. When the year-by-year increase attained in the respective groups is compared with that on the check plot, the effect of the implemented interventions can be shown to have resulted in as much as a 2.5 multiple of the height increment.


It has to be noted that the establishing of the comparison trials has not been correct at the beginning as regards then order of the plots. When looking at the records nowadays the arrangement A-B-C (fertilized-unfertilized-fertilized) seems to be rather a mistake since the influence of fertilized areas on both sides on an unfertilized area in-between obviously manifests itself by diffusion of the fertilizer nutrients over the whole area. Nonetheless the effect of fertilization on an increase in the increments is evident.


An important matter is also the question of the health condition and perishability rate of the planted seedlings. The following Table 1 shows the situation as regards the perishing (comparing the initial state of the culture inclusive of the increases owing to the improvements, with the number of growing seedlings in 1989 i.e. in the six years old culture).


Table 1. Perishability  of Seedlings in 1984 - 1989 in Groups

Group Year (% of the Number Compared with the Initial State)
1984 1985 1986 1987 1988 1989
A 100.0 100.4 109.2 106.0 97.6 92.0
B 100.0 102.3 105.6 101.1 100.8 95.5
C 100.0 95.1 107.5 103.0 100.8 97.7
D 100.0 79.6 87.4 118.3 102.5 106.1


After the improvement in the period 1985-1986 the first two groups A na B exhibit a nearly natural balance as regards the self-thinning (the situation of the group C where the improvement was effected in 1986 is similar); on the other hand the control group D shows a high and unnatural perishability caused, no doubt, by the unfavourable soil medium. Besides the lower increases the seedlings are weak, non-vital and readily affected by foreign influences.



With reference to the ascertained results of the biometric measurements to the results of analytical measurements as given in the RIIC report "A Fertilizer for Establishing Forest Cultures in Immission Affected Regions" (summary report for the period 1985 - 1988) and to the real conditions that can be demonstrated any time, it may be stated that the suggested fertilizer (fertilizer tablets SILVAMIX®) is suitable for the large-scale application and in demand by large-scale users.


August 6th, 1990