A more intense and mass production of medical aromatic plants, implementation of plantation system growth as well as the introduction of 150 standard system agricultural technology require a complete and more detailed study in order to perform a safe and economic production.

The territory of the Republic of Serbia, although relatively small compared to the area of Europe and whole planet, offers a significant climatological diversity conditioned by the position overlapped with various climatic influences (continental and maritime climate), relief and soil type diversity, exposition and other influences.

Thirty years series of meteorological parameters out of the network of 25 principal meteorological stations on the territory of Serbia were used in this paper. The average variation range and average occurrence of certain meteorological parameter values were taken into consideration in mean (average) value analyses.

The air temperature values in the surface layer of the atmosphere as well as the precipitation amounts, being the two most significant climatic factors in plant production were treated in details. Other meteorological factors (insulation, wind and icing) do not represent the limiting meteorological factors and therefore they were not taken into consideration.

1.1. Average dates of certain temperature occurrences

Average (mean) dates of maximum, minimum and mean daily temperature occurrences are given in Table 1. Average temperature duration in active vegetation (above 5°C) covers the period March 14 - November 23, having an average duration of 254 days.

The intensive vegetation period (t>10°C) usually lasts 206 days in average. The average duration of permanent frost period over the territory of Serbia in 103 days, from November 29 till March 12. The longest local duration of frost of frost period is in Pozega (120 days) and the shortest one is in Belgrade (61 days). Surface frosts (at 5 cm) occur early in autumn (November 21) and stop later in spring (March 22). In autumn, the period with episode occurrence of frost starts in average on October 18 and ends in spring, around April 20.

1.2. Average occurred sums of effective temperatures above certain biological thresholds

Biological effective temperatures (Table 2) start with temperatures above 5°C. Here we give two periods having the significance to certain plants with moderate heat requirement or to the plants with active vegetation interruption due to the occurrence of the rest period, i. e. the temperatures below 5°C.

The autumn period of occurrence from October 1 till the cessation of the occurrence (November 23) has the average sum of 227°C (Zaječar) and 328°C (Belgrade) respectively, i.e. the difference of 101°C. This sum divided daily minimum need of 5°C results in 20 days difference between the locations with maximum sums and the locations with minimum ones. As for the spring period having the mean daily temperatures above 5°C, it usually lasts from March 14 the end of June giving the average sum of these temperatures 1067°C (from 884°C in Pozega to 1115°C in Belgrade). For the plants that finish their vegetation season in this period, there is the difference in possible vegetation duration of 46 days over the territory of Serbia (from the locations with minimum sums to the locations with maximum ones).

Temperature sums above 10°C represent the zones of intense vegetation of plants with moderate heat requirements. The territory of Serbia in average has the value of 1464°C. The minimum value is 1234°C is recorded in Požega, while the maximum value 1691°C is recorded in Belgrade. The difference of these temperature values of 457°C in average represents the difference of 46 days in possible vegetation with daily requirements of 10°C. Such a big difference between temperature sums offers a possibility of location choice to cultivate various varieties in accordance to the vegetation duration and requirements in specific development phases.

Temperature sums above 15°C and 20°C give a thermal possibility of growing plants with high heat requirements. Average period with temperatures higher than 15°C over the territory of Serbia occurs from May 6 to September 28. The temperature sum of 601°C in average are reported, from 438°C in Požega to 755°C in Belgrade, showing the difference of 311°C representing 21 days of different duration periods over territory.

Temperature sums above 20°C represent the zone of generative stage in plants with moderate heat requirements. The territory of Serbia usually shows 69°C of these temperatures in the period June 22 - August 25. Local difference is 132°C and it represents the difference of the temperature in Požega (10°C) and Negotin (142°C). The spatial distribution of before said temperature sums over the territory of Serbia is given on Charts 1-4.

This regime is given by the table and chart presentations (Table 3 and Charts 5-7).

2.1 Precipitation amounts in the resting period of vegetation (winter moisture storage)

The average amount of effective precipitation in winter period (with subtracted losses due to evapotranspiration) in vegetation rest period (November - March) is 212 mm (from 154 mm in Palić to 252 mm in Negotin). The differences of 58 mm between the locations with maximum sum values and the locations with minimum sum values points out the significant difference in average precipitation amounts that represent the winter moisture storage that partially compensate permanent plant moisture deficit in warm (vegetation) part of the year.

2.2 Precipitation in vegetation season

In the period of full vegetation, the precipitation amount of 368 mm in average is reported (from 312 mm in Zaječar to 466 mm in Loznica). The difference of 154 mm indicates the territorial difference of water regime in growing plants and other habitat conditions. If we subtract the evapotranspiration losses from the amount of delivered precipitation in given thermal conditions, we get the moisture deficit. The moisture deficit is nearly constant over the territory of Serbia in the vegetation period, having the value of 152 mm. The highest moisture deficit is found in Nis (215 mm) and the lowest one in Valjevo (58 mm).

From the average delivered amount of winter effective precipitation (212 mm), about 100 mm remains as effective (available) moisture storage (the rest is lost due to infiltration or some other way). Only a small number of locations (Loznica, Valjevo, Kraljevo and Požega) can satisfy the demands of the plants for water. The large part of the territory of Serbia requires a permanent intervention by irrigation in order to normalize the water regime of plants in the period of full vegetation.

1. The territory of Serbia enables the period of active vegetation of 254 days since temperature in that period is permanent above 5°C.

2. The sums of average temperatures above the threshold of 5, 10, 15 and 20°C show a significant local difference over the territory of Serbia thus representing significant energetic differences for metabolic processes.

3. Average delivered precipitation amounts in the period of full vegetation, i.e. in the period when the temperature is above 10°C, cannot cover the average evapotranspiration moisture losses so the irrigation with different dosages should be applied.

4. All temperature values, sums of temperature, precipitation and moisture deficit locally show significant differences that should be taken into consideration when choosing the varieties of growing plants and modalities of applied agrotechnical measures.

1. Meteorological yearbook 1, Climatoligaical data, for period 1961-1990 year. Hidrometeorological Institute of Serbia.

2. R. Sneyers, WMO-On statistical analysis of series of observations, Technical note N°143.

Graph 1. Spatial distribution of average effective temperature sums >5°C
in period 01. 10.- 23. 11. over territory of Serbia


Graph 2. Spatial distribution of average effective temperature sums >5°C
in period 14. 03.- 30. 06. over territory of Serbia


Graph 3. Spatial distribution of average effective temperature sums >10°C
in period April - September over territory of Serbia


Graph 4. Spatial distribution of average effective temperature sums >15°C
in period 06. 05.- 28. 09. over territory of Serbia


Graph 5. Spatial distribution of average amount of effective precipitation in winter period
for period November - Mart


Graph 6. Spatial distribution of average amount of effective precipitation in vegetation period
April - September


Graph 7. Spatial distribution of average deficit of moisture (P-PET)
in period April - September