Following land surveys and on-site investigations, soil profiles have been opened to establish the global soil fertility status and the presence of hazardous and harmful substances at the level of the experiment field. Based on the analyses of water-physical and chemical properties of the samples taken in the profiles, soil types have been identified and a soil map at the level of soil form has been made. To get a better insight in the soil fertility status and the distribution of hazardous and harmful substances, the experiment field has been subdivided in 3-5 ha elementary plots. Samples from the profiles and those taken for soil fertility testing have been analyzed for the contents of microelements and heavy metals. Based on the criteria for the production of safe food, recommendations have been made and maps have been drawn of the areas in which the selection and seed production of medicinal herbs may be conducted without risk of contamination of their vegetative and/or generative parts. Taking in account the soil requirements of individual medicinal crops, most favorable plots have been identified at the experiment field and their locations have been mapped.
Key words: fertility, microelements, heavy metals, medicinal herbs.
Optimum conditions are needed for a successful seed production. While seed quality and genetic purity are secured by spatial isolation, yield quality and level depend on soil conditions. Seed production should be organized in field with a soil possessing good biological, physical and chemical properties. For a successful breeding and seed production of medicinal herbs, it is necessary to have a quality soil, rich humus, a regulator of soil physical properties and a source of essential elements (Brabenec, 1983). According to Tucakov (1984), there are eighteen requirements that should be met in order to achieve high quality of medicinal herbs. The requirement that concerns soil calls for a high quality irrigable soil.
The objective of this study was to quantify the optimum soil properties needed for achieving high yields of medicinal herbs on the basis of an analysis of fertility parameters of production plots taken from a database gathered for the development of a soil map of Rimski Šančevi Experiment Field.
Following preparatory activities, a team of soil scientists determined the coordinates of observation points where soil profiles were dug. The profiles were made conventionally, to the depth of 2 meters. After taking photographs and making morphological descriptions, undisturbed and disturbed soil samples were taken from different horizons for laboratory analyses. A total of 42 profiles were made. The next step was to locate the elementary plots for soil fertility control. They varied in size from 3 to 5 hectares. In the 189 elementary plots thus established, soil samples were taken from the depth 0-30 cm. Physical, chemical and microbiological properties of the samples were analyzed in the Laboratory of Agroecology, Department of Soil Science, Agroecology and Mineral Fertilizers, Institute of Field and Vegetable Crops, using methods accepted by the Yugoslav Society of Soil Science (JDPZ).
Map 1 shows that 44 plots from the Experiment Field meet the criteria for optimum soil properties needed for the breeding and seed production of medicinal herbs. The total size of these plots was 124.59 ha. In other words, 24% of the total area of 600 ha of Rimski Šančevi Experiment Field were found to possess optimum conditions necessary for the breeding of medicinal herbs and for obtaining high and stable seed yields. The key question was - which soil properties depart from the optimum values? The analysis provided the following answer: soil reaction, contents of humus and CaCO3 and soil provision with available P2O5 and K2O.
The criterion set for pHKCl was the interval from 6.5 to 7.5. Map 2 shows that the optimum pH was found in 137 plots. Slightly acid reaction (pH 5.5.-6.5) was found in 26 plots, acid reaction in 1 plot, alkaline reaction in 5 plots. This was an indication that, with the exception of plot no. 3495, soil reaction is not a limiting factor for seed production of medicinal herbs in the plots of the Experiment Field. Plot no. 2-5 and the neighboring plots 2-4 and 2-12 should be treated with 10 t/ha of CaCO3 in order to bring the soil reaction in them to the minimum level of 6.5.
The content of free CaCO3 (Map 3) was in correlation with soil reaction - plots with low pH contained no free CaCO3. The level of CaCO3 up to 2% was registered in 95 plots. This criterion should be set at a level higher than 2% in order to ensure stability in soil structure and favorable water-air regimen. Map 3 shows that free CaCO3 was absent in 17 plots. The problem may be overcome by liming.
Optimum humus content, higher than 2% and with the mean value of 2.85%, was registered at the entire territory of the Experiment Field. Only one plot had the humus content of 1.99%.
Soil provision with ammonium-lactate-available phosphorus was variable. Map 4 shows that the level of Al-P2O5 optimum for seed production of medicinal herbs was found in 88 plots with the total size of 283,7 ha. Furthermore, 18 plots had the content of Al-P2O5 above 50 mg/100g of soil. If these plots are to be used for seed production, phosphorus fertilization should be omitted in them. The phosphorus contents below 15 mg/100 g of soil was found in 41 plots. The mean content in them was 12.58 mg/100g. These plots do not meet the criterion for optimum phosphorus content, but it may be easily compensated with intensive phosphorus fertilization. The costs of extra phosphorus fertilization will affect the economy of seed production in the year of application but, because of the effect of soil reserve associated with phosphorus, this practice will improve the total fertility of soil.
On 39 plots the content of P ranged in the interval from 5 to 10 mg/100g of soil. The mean value was 7.96 mg/100g. It was recommended for these plots to be omitted from the program of breeding and seed production of medicinal herbs. Such production is not sufficiently accumulative to cover the costs of the necessary level of phosphorus fertilization.
The content of potassium was suitable for the breeding and seed production of medicinal herbs in almost all plots. Exceptions were 8 plots with the content of ammonium-lactate-available K2O above 50 mg/100g of soil. However, the mean content for these plots, which was 57.5 mg K2O /100g, cannot be a limiting factor for the breeding, seed production and production of planting material of medicinal herbs.
The contents of microelements (Cu, Zn, Mn, Mo) were at the optimum level or a high level on the entire territory of the Experiment Field.
The contents of the analyzed available and total heavy metals (Cd, Pb, Cr, Ni) were far below the values of minimum allowed concentration (MAC). Therefore, the Experiment Field is suitable for a risk-free and high production of quality seed and planting material of medicinal herbs. Favorable conditions and optimum levels of provision with biogenous elements ensure the profitability of such production.
The following conclusions were drawn.
Optimum soil conditions for the breeding and seed production of medicinal herbs exist at the area of 142.59 ha.
Soil reaction below pHKCl=6.5 and absence of free CaCO3 may affect the profitability of production in some plots.
The soil of the Experiment Field is well provided with humus, available microelements and potassium.
Phosphorus provision is highly variable. A part of the plots has an optimum content of available P, the other part requires fertilization with P2O5.
The contents of available and total heavy metals are far below the values of minimum allowed concentration (MAC), allowing a risk-free production of high quality seed of medicinal herbs.
Barbarec M. (1983): Pestovanie liečivych rastlin na malych plochach, Svepomoc Praha.
Sekulić P., Hadžić V., Kišgeci J.(1998): Zemljišni uslovi za proizvodnju lekovitog bilja u opštini Bački Petrovac. Zbornik radova Lekovite sirovine. XIII, 55-61.
Tucakov J. (1984): Lečenje biljem, Izdavačka radna organizacija "Rad", Beograd.