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Tropical and subtropical plants are a part of vegetation on the Earth. Some of them, fruit-tree species, are grown on plantations for production purposes. When growing them, a high quality of edible parts of these plants is a basic requirement.


An optimum nutrition is an important part of modern technology of growing both tropical and subtropical plants. At present, there is a number of fertilisers on the market that meet specific requirements put on their application and nutritive value. Besides well-known pelleted and/or liquid fertilisers used above all for the needs of intensive farming (i. e. the so-called Fast Release Fertilisers - FRF) attention is being paid more and more frequently to the development of specific formulas based on original physico-chemical principles and with special methods of application; such product meet substantially better the requirements of a selective nutrition of plants.


Slow Rrelease Fertilisers of the SILVAMIX® series, a Czech product constructed on the base of Ureaform and magnesium potassium diphosphates, represent an interesting solution of this problem. These fertilisers are manufactured as tablets of various size and belong to the category of the so-called Slow Release Fertilisers (SRF). In contradistinction FRF, this group of fertilisers is characterised by a very slow release of nutrients into the soil and in case of SILVAMIX® fertilisers also by a non-ionogenic nature of basic nutritive material. These properties optimise the release of nutrients from SRF products and, as compared with FRF formulas, significantly inhibit the process of soil salinisation of soils which represents a serious problem in some (especially arid) regions.


A two-year experiment with SILVAMIX® FORTE fertiliser (NKP 17.5-16.0-18.5 + 9.0% MgO; manufacturer ECOLAB ZNOJMO spol. s r.o. Czech Republic) applied in tablets to selected tropical and subtropical fruit-tree species was established in glasshouses of the Czech Agricultural University, Institute of Tropical and Subtropical Agriculture in Prague 6-Suchdol. Selected were two plant species, viz. loquat (Eriobotrya japonica) and rangpur lime (Citrus limonia). The first one is a subtropical evergreen tree that is grown in the Mediterranean countries. It requires a high supply of nutrients, mainly before and during the period of flowering which takes place sometimes also in winter months and during the formation of fruits. The second experimental species belongs to a very abundant genus Citrus and is used in Brazil as a rootstock species for local cultivars of orange trees. It is relatively easy to grow this species and it starts early to bear flowers and fruit.


There were four groups of experimental plants: the first one (Control) was not fertilised at all. The second one was fertilised with granulated CERERIT®Z (NPK 10.0-9.0-14.0 + 1.3% MgO; manufacturer SYNTHESIA PARDUBICE, Czech Republic) only at the beginning of the experiment; thereafter no fertilisers were applied. Group 3 was dressed with the fertiliser SILVAMIX® FORTE on the soil surface and Group 4 received SILVAMIX® FORTE below the root ball. As the pot volume was approximately 0.5 litre, only a half of the tablet was applied in Groups 3 and 4; this corresponded with recommendations of the manufacturer (1 tablet per 1 litre of soil). In Group 2, an equivalent amount of the industrial fertiliser Cererit was applied.


In case of loquat, two parameters were followed, viz. height of plants and number of leaves while in that of rangpur lime only height of plants was measured in the first year of the experiment. The course of flowering and fruit formation were recorded in the year to follow.



The growth intensity of control plants was much lower than in other groups. Both groups fertilised with SILVAMIX®FORTE showed better growth increments and higher numbers of leaves (Tab. 1). To the end of the experiment, plants were infested with Cladosporidium sp. This infestation was manifested above all in Controls and in Group 2. Because of a balanced ratio of nutrients in the SILVAMIX®FORTE fertiliser and their gradual release and supply to the root system of plants, Groups 3 and 4 were more vigorous and the extent of their infestation with Cladosporidium was very small.

Table 1. Growth characteristics - Loquat (Eriobotrya japonica)

Experimental variant Height of plants Number of leaves
cm % pcs %
Control 99,21 100,0 33,79 100,0
CERERIT®Z 108,86 109,7 37,64 111,4
Silvamix®Forte (applied on the surface) 116,57 117,5 39,14 115,8
Silvamix®Forte (applied to roots) 113,07 114,0 39,07 115,6


Ragpur lime (Citrus limonia)

The Slow Release Fertiliser SILVAMIX®FORTE showed a very positive effect on flowering and fruit quality.

In the first year after the application of SILVAMIX®FORTE, plants showed higher growth increments. In the second year, however, these increments were not so marked. In this period, the major part of the growth energy of plants was expended to flowering and fruit formation (Tab. 2). Since January, nearly all plant in Groups 3 and 4 began to flower. They bored more flowers and their losses of both flowers and fruits were lower. Flowering was observed also in both remaining groups but the onset of blossom was delayed and the numbers of both flowers and fruit were not as high as in Groups 3 and 4.


Table 2. Growth characteristics - Ragpur lime (Citrus limonia)

Experimental variant Height of plants Fruit number
cm % pcs %
Control 62,70 100,0 5 100,0
CERERIT®Z 47,20 75,3 9 180,0
Silvamix®Forte (applied on the surface) 52,50 83,7 11 220,0
Silvamix®Forte (applied to roots) 41,70 66,5 19 380,0



As far as the long-term effects of reserve fertilisers were concerned, the tabletted SRF product SILVAMIX®FORTE showed explicitly its quality and efficiency. Experimental plants of the loquat species had also in the second experimental year an adequate supply of nutrients. This was demonstrated in higher growth increments and higher numbers of leaves (Fig. 1). In case of rangpur lime, SILVAMIX®FORTE fertiliser induced an earlier onset of fruit-bearing, abundant blossom, lower losses and better quality of fruit (Fig. 2). Besides, the SILVAMIX®FORTE fertiliser showed also a positive effect on the health condition of plants: they showed higher vigour, more intensive colour of leaves and better resistance to pests and diseases.


Application of this fertiliser can influence significantly not only economics of use of ornamental pot plants when decorating different types of rigid interiors but also (and above all) growing cultural plants on large-scale plantations.

There were no significant differences in results obtained after the application of tablets on the soil surface and/or in the soil. The method of application was dependent only on user's technology.



Fig. 1 : Growth characteristics after the end of experiment - Loquat




Fig. 2: Growth characteristics after the end of experiment - Rangpur lime