Design parameters of furrow forming and compacting roller of the combined seeder STS-80

G. Hristova1*, M. Dallev2, G. Tihanov1

1Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
2Department of Agricultural machinery, Faculty of horticulture with viticulture, Agricultural University of Plovdiv, 12 Mendeleev Blvd., 4000 Plovdiv, Bulgaria

(Manuscript received 22 June 2021; accepted for publication 10 August 2021)

Abstract. A turf seed drill (STS-80) has been designed, in which the seeds from the sowing machines are sent to the soil through seed pipes. The size of the seeds is relatively small, therefore it is a requirement for them to be sown at a depth between 0.5 cm and 1.5 cm. The drill allows the following operations to be performed simultaneously: soil furrowing, seed sowing, and soil compaction with a compaction roller. The structure of the individual bodies that make up the aggregate is essential for the smooth running of the work process. Two rollers have been developed, which allow the providing of the necessary agro-technical requirements for sowing grass seeds. The role of the roller mounted in the front part of the drill is to make furrows in the soil at a depth of 1.5 cm, where the grass seeds fall. The roller, located in the rear of the unit, dulls the surface of the soil after the seeds enter it. This creates additional dynamic force, which increases the degree of soil compaction and the intensity of destruction of soil aggregates at a certain mass of the roller.

Fertilizer monitoring using micromachined cantilever

Venkatesh K.P. Rao


Department of Mechanical Engineering, Birla Institute of Technology and Science, Pilani, 333031-Rajasthan, India


(Manuscript received 16 June 2019; accepted for publication 1 August 2019)


Abstract. In this study, we will create a grid of micro electro-mechanical (MEMS) sensors, which will measure the contents of soil, especially urea. This will inform the farmers about the condition of soil in real time, and thus allowing them to know how much fertilizer they need to add. MEMS sensor is placed in the soil to measure the soil content by chemical reaction with the fertilizers; its accuracy can be improved if these sensors are placed on multiple points, i.e., they are placed in a grid. In the present study, we designed micro-cantilever based gas detectors, to detect ammonia present in the fertilizers. Several designs were proposed to find the best fit for this purpose. Numerical studies have been carried out on the proposed designs, to evaluate the displacement sensitivity and the voltage developed in the piezoelectric layer, and the triangular cantilever was found to be the most sensitive cantilever for that purpose.

Effects of irrigation and fertilization on soil microorganisms

T. Dinev1*, I. Gospodinov2, A. Stoyanova3, G. Beev1, D. Dermendzhieva4, D. Pavlov3

1Department of Biochemistry, Microbiology and Physics, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2Agricultural Institute, 6000 Stara Zagora, Bulgaria
3Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
4Department of Applied Ecology and Animal Hygiene, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 8 January 2016; accepted for publication 29 February 2016)

Abstract. The purpose of this study is to determine the influence of nitrogen fertilization and irrigation on the total count of aerobic mesophilic microorganisms, moulds and yeasts in the soil. The experiment was conducted in three variants and samples were taken as follows: from irrigated and fertilized furrow; from irrigated non-fertilized furrow and from furrow without irrigation and fertilization. For determination of total number of mesophilic aerobic microorganisms, moulds and yeasts the samples were diluted and cultivated on medium sheets coated with culture medium according to the requirements of the microorganisms. Data analysis shows that fertilization has the strongest multiplication effect on the number of aerobic mesophilic microorganisms in soil (their number increases from 10.522 x 106 to 12.8 x 106 cfu/g), whereas the irrigation does not have any statistically significant impact. The multiplication of moulds and yeasts in this trial is stimulated mainly by the increased humidity. When irrigation is applied the number of moulds and yeasts increases from 1.158 x 105 to 1.407 x 105 cfu/g, while fertilization does not affect their quantity in a statistically significant way.


Application of NIRS as a rapid and alternative method for prediction of heavy metals content in soil

M.Todorova, S. Atanassova , B. Sitaula, D. Apturachim, P. Valkova, D. Dermendgieva

Abstract. Determination of heavy metals content in soil by acid or microwave mineralization and spectrophotometer measurement via AAS or ICP are sufficiently accurate, but they are time consuming and labour intensive. These methods are not flexible enough for environmental research. Application of near infrared spectroscopy (NIRS) as a tool for ecological assessment and monitoring of soil quality have been investigated recently. The reported results for determination of trace elements in soil by NIRS are controversial. The objective of this study was to investigate the application of NIRS as a rapid and nonexpensive method for determination of heavy metals content in soil. A total of 121 soil samples from the 0–20 and 20–40 cm layer were collected from Stara Zagora, Chirpan, Kazanlak and Gurkovo regions. Total Zn, Cu, Pb, Ni and Cd content in the investigated soil samples were determined by AAS using AAnalyst 800 Atomic Absorption Spectrometer, Perkin Elmer. Near-infrared spectra of all soil samples were measured using spectrophotometer NIRQuest 512, within the range from 900 to 1700 nm. PLS regression was used for developinged models related tested parameters to the spectra. According to the statistical parameters of a regression procedure the best accuracy of determination was obtained for total Cu content with correlation coefficient R=0.92 and RPD=3.9 for the calibration set of data and r=0.77 and RPD=2.3 for the test data. Models for determination of Cd, Pb, Zn and Ni content via near-infrared spectroscopy could be classified as with good to low accuracy of determination, according to the obtained ratio SD/SEC and SD/SEP.


Chemometrical analyses of Zn distribution between water and soil of dams in Chirpan Municipality, Bulgaria

N. Georgieva, Z. Yaneva, M. Todorova, R. Ivanova, N. Nizamov, P. Neicheva

Abstract. This study was designed to evaluate the ecological status and to define probable liquid/solid correlations of Zn distribution between dam waters and adjacent soils in Chirpan Municipality, as a part of a continuous water and soil assessment project of Stara Zagora Region. Zinc concentrations in the investigated water and soil samples were determined by atomic absorption spectrometry (AAS) on AAnalyst 800 Atomic Absorption Spectrometer, Perkin Elmer, over the period December 2009 – November 2010. The analysis of Zn temporal distribution in the dam waters revealed maximum heavy metal loading of the three surface water bodies during June 2010. The ecological assessment of the studied soil samples showed that Zn content in some of them surpassed the maximum permissible concentrations (MPC), according to Bulgarian state standards. Basic statistical parameters (standard deviation values), liquid-to-solid metal correlations, linear regression analyses and Principal component analyses (PCA) were used to rationalize and interpret the analytical data for both media. Relationships between Zn contents in dissolved (dam water samples) and particulate (soil samples) phases in Chirpan Municipality, ascertained a high degree of water/soil correlation during December 2009 (R2 0.9963) and July 2010 (R2 0.9033) in the three investigated compartments. Distribution coefficients (K ) of the trace metal between both phases presented as log K were in the range 1.98 – 3.26. The PCA confirmed the conclusions withdrawn on the bases of d d the chemical analyses and categorized the investigated sampling points into three classes – Class 1 (SP 216, SP 410A, SP 410-1A) with predominant Zn loading of the water bodies; Class 2 (SP 217, SP 418A, SP 418-1A) featured with excessive Zn soil contents; Class 3 (SP 215, SP 409A, SP 409-1A) with average levels of the heavy metal in both phases. The data of the present study provided a scientific basis for best-management practices of natural water and land use in the investigated municipality.


Effect of experimentally polluted water on the morphological characteristics on the leaves of two varieties of Triticum aestivum L. grown on different soil types

K. Velichkova, D. Pavlov, D. Ninova
Abstract. Two varieties of wheat were grown on different soil types (Calcic chernozem and Rendzina). The influence of experimentally polluted water was investigated on the morphological characteristics of the leaves of the two varieties. Manganese and ammonia have positive effect, while diluted concentrations of copper and magnesium have negative impact. The biggest changes in the morphological characteristics have been observed in the length of the leaves. Sadovo variety is more resistant to the impact of pollutants and has better performance which is important for the agricultural practice.


Effect of experimentally polluted water on the stomatal and structural characteristics on the leaves of two varieties of Triticum aestivum L. grown on different soil types

K. Velichkova, D. Pavlov, D. Ninova

Abstract. Two varieties of wheat were grown on different soil types (chernozem carbonate and humus-carbonate). The influence of experimentally polluted water was investigated on the stomatal characteristics on the leaves of the two varieties, and copper, ammonium and magnesium sulfate had inhibitory effect. Wheat variety “Yantar” had greater dimensions of the stomata, than variety “Sadovo” in the same soil. Variety “Sadovo” grown on carbonate chernozem had larger stomata compared to the same in humus-carbonate soil


Estimation of several soil properties by near-infrared reflectance spectroscopy

M.Todorova, S. Atanassova, H. Longer, D. Pavlov

Abstract. There is a great demand for involving rapid, non destructive and less time consuming methods for quick control and prediction of soil quality, environmental monitoring, and other precision measurements in agriculture. Near infrared reflectance spectroscopy(NIRS)is considered as an appropriate alternative method to conventional analytical methods for large scale measurements. The objective of this study was to investigate the possibilities of NIRS for prediction of some chemical properties of soil samples. A total of 97 samples from Stara Zagora, Kazanlak and Gurkovo region taken from the 0-40 cm layer were collected. Soil types were Luvisols, Vertisols, Fluvisols and Rankers. The samples were analyzed for total phosphorus by spectrometric determination of phosphorus soluble in sodium hydrogen carbonate solution, total nitrogen by Kjeldahl method, pH (H O)-potentiometrically and electrical conductivity (EC). 2 The spectral data of all air dried samples were measured using an Perkin Elmer Spectrum One NTS, FT-NIR Spectrometer, within the range from 700 to 2500 nm. Partial Least Squares (PLS) regression was used to built models to determine soil chemical parameters from the NIR spectra. Two-third of the samples were used as a calibration set and the remaining samples as independent validation test set. The best model was obtained for total nitrogen with a coefficient of determination r=0,91, standard error of calibration SEP=336 mg/kg, and the ratio of the standard variation of the reference data to the SEP, indicating the performance of the calibration, of RPD=2,3. The accuracy of prediction was poor for electrical conductivity. The results obtained clearly indicated that NIRS had the potential to predict some soil components rapidly and without sample preparation.


Variation in lipid abundance and composition in a fire affected hillside from Lyulin mountain, Bulgaria

Top soils from a fire-affected catena sequence on the Southern hillside of Lyulin Mountain, Bulgaria were analysed for free lipids with the aim to identify molecular markers of the effect of fire on soil organic matter. The total lipid extract of the unburned control soil was dominated by aliphatic series of  alkanes, alkanoic acids, alkanols, diterpenoids and steroids indicating the predominant higher plant input. The alkane patterns as revealed by the carbon preference index (CPI) and the average chain length (ACL) showed higher relative abundance of short chain homologues (C – C ) in the burned soils as 13 20 compared to the control soil and indicated a thermal, but also a microbial input. The fatty acids and alkanols signatures, as well as the typical biomarker signals for pine such as pimaric acid and methyldehydroabietate were lost in the chromatogram of the severely burnt soil on the ridge of the mountain. All samples displayed a particular pattern of short- and long-chain and even carbon numbered n-alkanes (maximum at C and C ). Aromatic hydrocarbons and 29 27 oxygenated acids were more abundant in the burnt soil on the ridge while the pine signals of pimaric acid and dehydroabietic acid disappeared.

Variation in lipid abundance and composition in a fire affected hillside from Lyulin mountain, Bulgaria

I. Atanassova, M. Teoharov

Microbial communities in areas affected by formation of calcrete in thracian plane

The number of 13 physiological groups of microorganisms is counted in depth of two types of alkaline soils affected by formation of calcrete. The first soil type is characterized by the presence of calcrete nodules occupying the surface layer of soil profile from 5 to 38 cm, and the second soil type – of isometric calcrete nodules, settled in depth below 30-35 cm. During the spring and autumn, when the samples were collected, it was determined that in soil, which is more affected by formation of calcrete, the number of various heterotrophic aerobic and anaerobic bacteria, actinomycetes and fungi is 1 to 3 orders lower than in less affected soil. A similar effect was observed on the amount of nitrifying bacteria. Other factors that influenced the microbial community structure and number were also the various values of pH, fractions of organic carbon and total nitrogen

Microbial communities in areas affected by formation of calcrete in thracian plane

S. Bratkova, K. Nikolova, K. Gesheva