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This paper presents the mechanical properties of soil. In order to determine the properties of soil under laboratory conditions, a special measuring device was constructed, viz. a bevameter. Two types of soil with different levels of moisture were examined and their mechanical properties were determined. Measurements were taken of non-compressed soil. A measuring network was set up, consisting of measuring and recording devices. In the course of measuring, the force and penetration depth of the pressing plate were recorded simultaneously. Three different diameters of pressing plate were used, namely 38, 50 and 70 mm. The pressure on the contact area was calculated after completion of the measurements, and the relationships between pressure and penetration depth were presented graphically.

Hardfacing is one of the most useful and economical ways to improve the performance of components submitted to severe wear conditions. This study has been made for the comparison of microstructure and abrasion resistance of hardfacing alloys reinforced with chromium carbides or complex carbides. The hardfacing alloys were deposited onto ČNS EN S235JR low carbon steel plates by the gas metal arc welding (GMAW) method. Different commercial hardfacing electrodes were applied to investigate the effect of abrasive particle size on abrasive wear resistance. The abrasion tests were made using the two-body abrasion test according to ČSN 01 5084 standard, abrasive cloths were of grits 80, 120, 240, and 400. Microstructure characterisation and surface analysis were made using optical and scanning electron microscopy. The results show the different influence of abrasive particles size on the wear rate for different structures of Fe-Cr-C system. The structures without primary carbides are of high abrasive wear rate, which increases nonlinearly with the increasing abrasive particle size. On the contrary, the structures containing primary carbides are of low abrasive rates and theses rates increase linearly with the increasing abrasive particle size.

The accelerated laboratory tests can evaluate the properties of new biodegradable fluids under relatively short time. These test results are the ground for the continuity of the tests under operation conditions in machine. The paper presents the test of new biodegradable hydraulic fluid type "Environmentally responsible tractor transmission oil" by designed special test device. The test evaluation was realized by technical state of concrete hydrostatic pump UD 25 which is used in tractors Zetor Forterra. This pump was loaded by cyclic pressure loading during the test with tested fluid. The evaluated parameter was flow efficiency of hydrostatic pump which reached the value 7.3% after the test. The reached value hints a high quality of the tested fluid (the limit value per standard is the flow efficiency decrease - 20%).

This paper deals with the Reynoutria × bohemica and Reynoutria japonica under conditions of the Czech Republic. It evaluates the impact of soil, weather conditions and various terms of harvest (autumn, spring) on the yield, dry matter content, phytomass loss, ash content, and basic elements content change in plants. Heavy metals content was determined in soil where plants were grown and consequently in plants themselves. The average yield of dry matter at the fully closed stands of Reynoutria japonica were 9.06 t/ha in autumn, Reynoutria × bohemica from 13.23 to 21.41 t/ha, according to the site. The yield losses within the winter period were found on average 42% for Reynoutria japonica and 34% for Reynoutria × bohemica. The moisture decrease of Reynoutria japonica was found from 68% in the autumn to 24% in the spring, and of Reynoutria × bohemica from 67% to 23%, respectively. Decreased content of nitrogen, phosphorus, potassium, calcium, and magnesium in the knotweed phytomass was found during the latter (spring) harvest periods in comparison with the earlier harvest periods. Decreased elements content in phytomass during the latter harvest period (spring) increases the phytomass quality as a fuel from both aspects - technical and emissions generation. The ash content in plants varied according to the site, on average from 3.12% in Ruzyně to 4.6% in Chomutov. None of the heavy metals monitored in knotweed plants reached the maximum admissible values determined for the food or feed purposes in the Czech Republic. From the results of combustion experiments, it is evident that Reynoutria × bohemica is a good fuel. Energy sorrel shows the extreme CO concentration in flue gases in comparison with other monitored fuels. According to the ČSN EN 12809 (2001) standard it does not meet even the third class of requirements. On the contrary, knotweed and wood bark fulfill the requirements for the first class. The surprising fact is that both of these fuels show the lower level of CO emissions, than the wooden briquettes. Concentrations of nitrogen oxids are comparable with biofuels, except of wood, and probably are related to the nitrogen content in heating material.

This study was conducted with the aim to evaluate the effects of the moisture content, internode position, and loading rate on the bending characteristics of barley straw including bending stress and Young's modulus. In the study, 9 treatments were performed as randomised complete block design with 5 replications. The characteristics were determined at three moisture levels: 10%, 15%, and 20% wet basis, three loading rates: 5, 10, and 15 mm/min, and free internodes: the first, second, and third internodes. The results showed that both the bending stress and Young's modulus decreased with an increase in the moisture content and towards the third internode position. The average bending stress was obtained as 8.41 MPa varying from 6.32 to 12.41 MPa, while the average Young's modulus was calculated as 473.88 MPa ranging from 330.94 to 618.91 MPa. As shown by the results obtained, the values of the characteristics increased with increasing loading rate.

In present days composite materials are the indispensable part of many branches. They make a foray into the branch of agricultural production, where they are getting to intensive development of systems utilized e.g. at soil processing. Composites can be defined as materials which synergically combine properties of matrix and filler. One of possibilities of polymeric particle composites preparation is the application of suitable filler together with some types of epoxy resins. This application extends the usable properties of resins. For the exact definition of these materials use it is necessary to map their behaviour. In the paper the problems are described, which concern the composite hardness changes as a consequence of the filler particle sedimentation in the course of the resin curing. The composite matrix was the two-component epoxy resin and the filler were chips of materials cutting process. The use of waste filler suggests itself the ecological possibility of recycling, which should be preferred in consideration to the environment friendliness.

The present study investigates the possibility of the non-destructive prediction of the main quality indices of commercial eggs by calculating the ultrasound phase velocity within the egg material. The phase velocity of the ultrasound signal in the egg material was determined by analysing the recorded ultrasound signals using the Fast Fourier Transform. Three hundred commercial eggs (Boris Brown, 33 weeks age) from the first day of egg laying were purchased from a farm and divided in two groups. The first group was kept at the room temperature (22-25°C) and the second group was kept in a refrigerator (5°C). Every week, 25 eggs from both the room and the refrigerator were first submitted to the non-destructive ultrasound test at weekly basis at the room temperature. Immediately after testing, the air cell, the thick albumen heights, the Haugh unit and the yolk index of the eggs were also determined destructively for the comparison purposes. The results were analysed to find any possible correlation between the computed ultrasonic phase velocity and the destructive parameters, during a storage period of five weeks. The tests were carried out using an ultrasound beam with a frequency of 150 kHz with a sampling rate of 2.5 Gs/S on the eggs under a controlled temperature situation. Significant differences between the means of the destructive analysis on different days of the eggs storage were found using ANOVA. The results showed that the phase velocity significantly differs between the eggs stored at the room temperature and those stored in the refrigerator. It was found that the phase velocity decreased as the storage time of the eggs increased in three consecutive weeks.

The present paper is aimed at the use of satellite navigation of field machinery during seeding, this operation belonging to the most important field practises. Our attention was focused on the determination of the accuracy of the satellite navigation system based on using the correction signal real-time kinematic and its correct application for planting a wide-row crop (sunflower) and seeding a narrow-row crop (spring barley). The aim of the field experiment was also to specify the level of the necessary accuracy of satellite navigation systems during planting and seeding. The length of seeding/planting equipment was confronted with the accuracy of navigation of individual passes, especially when turning on the headlands. In the conclusion, the importance is highlighted of the automated tractor headland control during satellite navigation of combined field machines in the crop production.

The numerical mathematical theory provides a few ways of numerical integration with different errors. It is necessary to make use of the most exact method with respect to the computing power for a majority of microprocessors, because errors are integrated within them due to the algorithm. In our contribution, trapezoidal rule and Romberg's method of numerical integration are compared in the velocity calculation algorithm of the strapdown inertial navigation. The sample frequency of acceleration and angular velocity measurement was 816.6599 Hz. Inertial navigation velocity was compared with precise incremental encoder data. Trapezoidal method velocity error in this example was 1.23 × 10^-3 m/s in the fifteenth-second measurement. Romberg's method velocity error was 0.16 × 10^-3 m/s for the same input data. The numerical mathematical theory provides a few ways of numerical integration with different errors. It is necessary to make use of the most exact method with respect to the computing power for a majority of microprocessors, because errors are integrated within them due to the algorithm. In our contribution, trapezoidal rule and Romberg's method of numerical integration are compared in the velocity calculation algorithm of the strapdown inertial navigation. The sample frequency of acceleration and angular velocity measurement was 816.6599 Hz. Inertial navigation velocity was compared with precise incremental encoder data. Trapezoidal method velocity error in this example was 1.23 × 10^-3 m/s in the fifteenth-second measurement. Romberg's method velocity error was 0.16 × 10^-3 m/s for the same input data.

This work is aimed at the evaluation of the operating parameters and emission of two tractors: Hürlimann H-488 DT and Hürlimann XB Max 100. The measurements were done on a test bench in the laboratory of the Agroscope Reckenholz-Tänikon Research Station ART, Ettenhausen, Switzerland during February 2010. The goal of this paper was to evaluate the operating parameters of the two models of tractors by using classical diesel oil and biofuel, as well as to evaluate the emission (greenhouse gases, dangerous exhaust gases and carcinogens), to make statistical analysis of the results and the conclusion about the samples used and the impact on engine parameters, environment and human health. From the results achieved, it is possible to state the following facts. In each way, the emissions of rape seed methylester (RME) and diesel are equivalent. The values of CO and HC and also particles are lower for RME. But NO_x values are lower for diesel oil. It is liquid that the newer engine of Hürlimann XB Max 100 decreases emission of CO, HC and NO_x significantly.

The paper evaluates the surface roughness quality of the titanium samples created by abrasive waterjet (AWJ) and by CO₂ laser beam cuttings. The introduction describes the principle of the mechanical (contact) method as well as the roughness parameters used for the experiment results evaluation. The following parts summarise the experimental conditions and the measurement methodology. The emphasis of this work is laid on the comparison of machined surfaces final quality for the selected traverse speeds.

A design of the motion screw using the method of stress limit is described. Further general formulas are induced to design such kind of screws, applied to an example of 11500 (EN ISO E295) steel made screw, strained by static operational force. Safety equations to prevent screw drift and their diagrams are integrated parts of the article.

The paper deals with assessment of biogas yield from mixtures of Reynoutria substrates and livestock manure. The aim was to perform laboratory experiments and suggest suitable fermenter operating conditions (dry matter content, pH, share of substrate components, thermic regime) for metanogenic digestion, then to determine its quality and assess the usability of such produced biogas.

In accordance with the technical standard ČSN EN 13229 "Inset appliances for heating including open fires fired by solid fuels - Requirements and test methods" was performed the basic assessment of thermal efficiency and emission parameters of prototype of combustion accumulation stove SK-2 with upper after-burning and nominal heat output of 8 kW. Verified gradually were the bio-briquettes of diameter 65 mm from mixture of wheat straw and 20% m/m of brown coal, wheat straw and 5% m/m of brown coal, wheat straw, mixture of wheat straw and 10% m/m of water and molasses solution, Ecobiopal created with the fermented blend of 33% m/m of digested clean water plant sludge and 67% m/m of wood chopped material, blend of wheat straw and 15% m/m of sugar beet pulp, mixture of timothy hay and 25% m/m of brown coal, timothy grass hay, meadow hay, mixture of meadow hay and 25% m/m of brown coal. The lowest CO emissions, when the limit value of 3000 mg/m³_N at 13% of O₂ has not been exceeded, determined for more strict 1^st class and the highest efficiency at nominal heat performance, i.e. higher or equal to 70% (Class I) have been reached by the briquettes produced from mixture of wheat straw and 15% m/m of sugar beet pulp, timothy hay and mixture of meadow hay with addition of 25% m/m of brown coal. Further were measured NO_x and HCl emissions. NO_x values were significantly lower than limit values determined for similar combustion of solid biofuel. Higher differences of HCl emissions correlate with various Cl content in fuels. Only the wheat straw briquettes with share of 25% m/m of brown coal have exceeded the limit value by 16%. Other fuels have shown considerably lower values. The results have proved better heat-technical and emission parameters of blended briquettes and are significant also for solid biofuels and solid recovered fuels standardization as well as for increasing efficiency method detection and ecological parameters optimization including HCl emissions.

The basis of the biogas production in agriculture is the processing of waste agricultural products (particularly excrements of farm animals but also phytomass). Different but rather similar is the biogas production from biologically degradable municipal waste (BDMW) and biologically degradable industrial waste (BDIW) coming mainly from food industry. The processing of these wastes in agricultural biogas stations could significantly improve their economy. It is necessary to note that all these biogas stations differ from the wastewater cleaning plants where municipal sludge water from public sewers is processed. The municipal sludge water processing to biogas by anaerobic fermentation is a classical technology introduced all over the world. At present, about 100 wastewater cleaning plants operate in the Czech Republic using regular sludge processing into biogas. Electricity produced is utilised mainly for the needs of own operation of waste water treatment plant (WWTP), partly it is sold into public power net. The heat energy is used for heating in the process and its surplus is utilised for operational and administrative facilities. Usually, the heat and electricity quantities produced do not cover the wastewater cleaning plant operation. Agricultural biogas stations and biogas stations for BDMW processing provide considerably higher gas yields because they work with higher dry matter contents in substratum, i.e. 8-12% (compared with waste water treatment plants - 2-6%), and are able to produce high gas surpluses for following applications. Frequently discussed issue are the processing of slaughter waste and grass (or public green areas at biogas stations).

Force and deformation curves of agricultural materials must be provided for the proper design of harvesting and processing machineries. In this research, the fracture resistance of barley grain was measured in terms of the grain rupture force and energy. In this study, 8 treatments were performed as a randomised complete block design with 10 replications. The barley grains were quasi-statically loaded in horizontal and vertical orientations with the moisture content at four levels: 7.34, 12.11, 16.82, and 21.58% dry basis, and loading rates at two levels: 5 and 10 mm/min. Based on the results obtained, the force required for initiating the grain rupture decreased from 161.97 to 93.94 N, and from 75.37 to 50.16 N, and the energy absorbed at the grain rupture increased from 36.42 to 74.70 mJ and from 27.34 to 62.65 mJ, for horizontal and vertical orientations, respectively, with the increase in the moisture content from 7.34 to 21.58% dry basis. This showed that seeds are more flexible in the horizontal orientation.

: The article is focused on the analysis of the bonded metal joints capacity and corrosion weight losses in the conditions of equatorial Indonesia - North Sumatra province. For the purpose of the given article, the province was divided into three main climatic zones: Medan, Balige, Pagarbatu, where the dependence was observed of the bonded joints capacity on the duration of the weather exposure. The joints life and their further usability were predicted based on the analyses of the measured values.

An expert estimate of the weight of emissions produced in agriculture has been up to now made only through a final counting to the total REZZO 4 emission balance in the category of "other mobile sources" The existing situation is however unbearable since a proper methodology to determine the production of emissions in agriculture, i.e. in the department with a considerable consumption of fossil fuels, is still missing. The solution consists in a more precise specification of the weight of generated limited pollutants (CO, NO_x, SO₂, PM and VOC including CO₂) in the department of agriculture on the basis of the measured annual consumption of fuels in agriculture and with using the emission factors of fuels. Calculated results are compared with the original values finally counted for the REZZO 4 category of "other mobile sources" in 2000 and 2001 (Adamec 2002; Adamec et el. 2003). The calculation revealed that the weight production of individual pollutants in 2000 and 2001 reached only 28% and 27% for CO, 52% and 50% for NO_x, 69% and 66% for SO₂, 87% and 83% for PM, and 26% and 24% for VOC of the original estimates with final counts and was therefore much lower. The share of agriculture in the weight production of emissions from mobile sources in 2000 and 2001 was 3.1% and 3.1% for CO, 11.5% and 11.5% for NO_x, 19.8% and 18.8% for SO₂, 38.3% and 34.6% for PM, and 3.5% and 3.6% for VOC. The development of weight production for individual pollutants in the period from 1995-2005 is expressed by means of regression equations. Coefficients of reliability indicate that the measure of reliability of the interval determined by calculation is much higher than that of the reliability interval determined by values estimated through final counting that appear incidental. There are increasing efforts today focused on the replacement of diesel oil as a traditional fossil fuel in agriculture with biodiesel oil as a more environment-friendly fuel. The second part of results includes a monitoring of the impact of biodiesel oil emissions in cases where diesel oil was replaced by this ecological fuel in agriculture in the period from 2000-2005. It follows from the analysis that the weight production of pollutants in 2000-2005 would have been reduced by 4% in CO, by 28% in SO₂, by 52% in PM and by 4% in VOC while an increase by 20% and 32% would have been recorded in CO₂ and NO_x, respectively. Regression equations are used to express the development of the weight production of individual diesel oil and biodiesel oil pollutants in the period from 2000-2005. Reliability coefficients that are of constant character indicate that the development of the weight of pollutants from diesel oil replicates the development of biodiesel oil pollutants. The significance of achieved results consists in the provision of a more accurate general balance of emissions from one of so called other mobile sources in Czech Republic (apart from the department of transport), thus contributing among other things to a more accurate expression of the total weight of emission production within REZZO 4.

The appearance of fruits and vegetables has a major influence on the perceived quality. Therefore, colour is one of the most important quality parameters in consumers' preferences. Fruits differently exposed to the sun differ in colour, frequently looking unripe and reach full maturity just on handling or transport, some still green and appearing unripe. Oranges, carrot, red beet, and parsley were used for the study of the quality estimation. Different nets used for the packing of fruits were tested. The measurements of lightness and chromaticity parameters were performed according to L*a*b* system. The red net used for the packing of oranges caused a decrease of the lightness parameter L* for all stages of fruits maturity. However, some unripe and bright oranges, through the use of a red net, looked more mature. The chromaticity parameter a* is the most influential factor affecting the human perception of the fruit colour. The red net improves this parameter significantly, thus unripe yellow oranges become more saturated, changing the perception of colour to the predicted range. The colour is insignificant for the net, however, it is important for the classification and quality assessment by humans.

This article describes the results of the analysis of correlation between the soil electrical conductivity and BPEJ (valued soil-ecological units). The measurements were made in 2006 at the School Agribusiness Land Farm in Lány established by the Czech University of Life Sciences in Prague. The soil electrical conductivity (EC) was measured by the contact method using a sensor with six electrodes. The soil EC data measured were compared with the data obtained from BPEJ maps. The aim was to verify if any relationship exists between the soil EC and BPEJ. The results achieved show that the same dependency exists between the values of the main soil unit of the BPEJ code and the soil EC. The results achieved can be used in the precise agriculture system to improve the decision process.

In the Czech Republic the increased utilization of the biofuels, especially for diesel engines, has been registered in the last ten years. The rape-seed oil based fuels - called biodiesel, is the most extended. The use of rape-seed oil brings a good ecological and agronomic aspect, e.g. positive energetic and CO₂ balance, biological decomposition, etc. A special attention should be paid for the emissions. The paper presents the practical results of the performance with the commercially available biodiesel and their mixtures with different quantity of fermented ethanol. The testing was realized with an unmodified AVIA 712.18 truck engine and an unmodified ZETOR 7701 tractor engine according to thirteen-points homologation test method EHK R49 (ČSN EN ISO 8178-4). Biodiesel NATURDIESEL, according to the Czech Standard ČSN 65 6508, served as a basis for fuel blends and such a comparison fuel. Based on the experiment, it can be said, that the most suitable fuel blend is biodiesel + 2% addition of fermented bioethanol according to following points. This addition significantly reduces the NO_x emissions. At the AVIA engine the reduction is about 54% in comparison with non-additived fuel. With the Zetor engine, it is decreased 88% of its primary value. Even in cause of smokiness, the situation is similar favourable. The power output parameters are almost constant. No significant increase of fuel consumption has been observed. However, there is higher share of unburned hydrocarbons in dependence on increased alcohol content. In this case, the lower concentration of alcohol in fuel blend is advantageous, which is in accordance to the biodiesel with 2% addition of alcohol. Higher share of ethanol is not interesting from the point of view of fuel requirement and even from the economic point of view, because the price of these fuel blends increases, due to the co-solvent addition.

The power requirement of tillage implements is an important design consideration particularly for animal-drawn implements where the power is limited. The paper presents the possibility of reduction in the draught requirements of animal-drawn mouldboard plough by using enamel coating on the soil-engaged components such as the mouldboard, share and the landside. Trials were conducted to compare enamel-coated Maun Series single mouldboard plough (manufactured by Zimplow Limited, Bulawayo,Zimbabwe) with similar uncoated plough, both animal-drawn, under comparable working conditions. Experiments were done at 25% and 32% d.b. soil moisture content on a red clay soil inZimbabwe. The parameters measured in evaluating the draught performance of both ploughs were the tractive effort (pull), speed of ploughing, depth and width of ploughing, and soil conditions (i.e. soil moisture content, soil bulk density and soil penetration resistance). It was found that for similar working conditions the enamel coating reduced the specific draught by 20 to 26% depending upon soil moisture content.

Potassium is one of the most important nutrients for plants and its content in the soil should be monitored. In the precision agriculture, which is recommended now, the ion selective electrodes are tested to determine chemical properties of the soil. The objective of this work was an evaluation of use of the valinomycin-based ion selective sensors for determination of assimilated potassium in Egner-Rhiem soil extracts. Flame photometry was used as a reference method. Results obtained from potentiometric and photometric methods in soil extracts correlated linearly (R² = 0.84). Analysis of soil extracts by the ion selective electrodes is simple and there is not a need for calcium ions precipitation.

Putting together work operations minimizes the number of machine passes across the plot, which helps to reduce negative soil compaction and to save fuels. However, the combination of working operations also reflects in the increased weight of machines, which - on the other hand - can result exactly in soil compaction. This is why the potential adverse phenomenon can be compensated by using tyres with a larger contact surface with the base. In the case of sowing root crops, some problems may appear with the application of these tyres as a certain part of the stand has been sown in their track. The paper brings an assessment of the possibility to use twin assembly tyres on the tractor model Fendt 822 and on the sowing drill model Monosem NG plus with 18 drilling mechanisms. Parameters to be assessed were soil compaction, and the development of plants sown inside and outside the tractor track. Although the degree of soil compaction was higher in the tractor track, the biological characteristic of plants including yield reached more favourable criteria of assessment. The situation paradoxically resulted from the creation of more favourable moisture conditions in the soil.

The main aim of this article is to evaluate the possibility of forage yield maps creating based on mowing machine's conditioner power input measurement. Strong spatial dependence was observed for conditioner power input data. For the data file from material feed rate measurement the medium spatial dependence was calculated. Relatively low value of variograms range is possible to explain by the type of chosen exponential model. Visual displaying of data distribution is done by the maps. These maps were plotted under kriging method. It is possible to observe distributions of higher and smaller values of conditioner power input and material feed rate measurement by this way. Plotted maps are shown in Figures. The correlation coefficients were calculated 0.419 for filtered data. It follows from this evaluation that conditioner power input measurement can be used for the determination of mowing machine material feed rate.

Physical properties of commercial fertilizers play important role from precision application point of view. Granulometric evaluation is usually performed by sieve separation according ČSN 01 5030 standard. The main subject of this work is the presentation of separation results when vertical airflow is used.

This contribution is oriented on the field of dynamic loading analysis of three-point hitch of tractor hydraulic pump. The hydraulic pump is placed in circuit of three-point hitch of the tractor ZTS 160 45. Obtained data from operation experiments will be applied for simulation of dynamic loading of the tested hydraulic pump. The measurements were realized during position control with ploughing sets: tractor ZTS 160 45 + plough 5-PN-30 and tractor ZTS 160 45 + plough 7-PHX-35. During the test physical and mechanical properties of soil and operating parameters of ploughing sets were investigated. Pressures of hydraulic system were in range from 3.2 to 7 MPa at aggregation with plough 5-PN-30 and hydraulic pump was loaded. Pressures of hydraulic system during ploughing with ploughing set tractor ZTS 160 45 + plough 7-PHX-35 were in range from 1.8 to 14 MPa and two times hydraulic pump was unloading in time 2 seconds.

The reed canary grass as a source of energy was tested in field experiments on small plots at three different sites in 1996-2003. The effects of soil and weather conditions, different times of harvest (July, November, March) and different doses of nitrogen fertilization (0, 30, 60 kg/ha) on yields of phytomass were investigated. The effects of the harvest time on the water content in harvested phytomass, loss of phytomass in different harvest period and the content of basic nutrients and heavy metals in plants were all specified. The influence of the year, site and N fertilization on yields of phytomass of the reed canary grass was highly significant. The reed canary grass responded positively to increasing doses of nitrogen by the increase of yields of phytomass. On the averages of years and sites, the N application dose of 30 kg/ha increased dry phytomass yields of the reed canary grass harvested in November by 14.6% (1.08 t/ha). The higher dosage of N 60 kg/ha increased yields of phytomass of the reed canary grass at all sites by 32.8% (2.08 t/ha) on average in contrast with variants without fertilization. By the dose of N 60 kg/ha, the dry above-ground phytomass harvested in autumn was 10.04 t/ha in Ruzyně, 8.27 t/ha in Lukavec and 6.94 t/hain Chomutov on average over the whole period. The later times of harvest resulted in a decrease of the average yield of phytomass (8.41 t/ha in July, 8.00 t/ha in November and 6.04 t/ha in March) and the average water content (64.3% - 45.2% - 21.5%); on the contrary, energy value of phytomass increased (16.93 GJ/t - 17.02 GJ/t - 17.19 GJ/t). The average content of ash in plants varied from 6.5% in Lukavec to 9.31% in Chomutov. The content of heavy metals in plants never exceeded the highest permissible values set in the Czech Republic for food and feed purposes.

In this research, leaf area prediction models were developed for some leaf-used medicinal plants namely Calamintha nepeta, Datura stromonium, Melissa officinalis, Mentha piperita, Nerium oleander, Origanum onites and Urtica dioica growing wild in Black Sea region of Turkey. Lamina width, length and leaf area were measured non-destructively to develop the models. The actual leaf areas of the plants were measured by PLACOM Digital Planimeter, and multiple regression analysis with Excel 7.0 computer package program was performed for the plants separately. The produced leaf area prediction models in the present study were formulized as LA = (a) + (b₁ × L) + [(b₂ × (L × W)] + (b₃ × L²) + (b₄ × W²) + [b₅ × (L × W²)] + [b₆ × (L² × W)] + [b₇ × (L² × W²)] where LA is leaf area, W is leaf width, L is leaf length and a, b₁, b₂, b₃, b₄, b₅, b₆, and b₇ are coefficients. R² values for medicinal plants tested varied with species from 0.82 in Origanum onites to 0.98 in Urtica dioica. All R² values and standard errors were found to be significant at the P < 0.001 level.