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Contents
PRODUCTIVITY OF CROP ROTATIONS AND THEIR IMPACT ON NPK MIGRATION IN AGROECOSYSTEMRamute AKSOMAITIENE, Ginutis KUTRA, Zita PETROKIENESummaryThe paper presents the generalized data on principal nutrient migration processes occurring within one rotation period of crop rotations of different intensity. It also deals with the relations among nutrient migration, agroecosystem productivity and the factors predetermining the productivity: crop structure, fertilization, and soil agrochemical characteristics. The studies were carried out in the basins of 5 drainage systems of 6-15 ha in Lipliunai, Kedainiai district, in 1995-2001. The studies were performed on the basis of different crop rotations: applying no organic fertilizers and having ploughed up by-products. Two kinds of crop rotations were studied: classical one and the field containing 50% of row crops, 100% of cereals, cereals with pulse crops and perennial grass. Field crop rotation is most productive. The whole annual yield of dry matter (main products, by-products and crop residuals) was 8.2-9.5 t/ha, 50-54% of which fell on the main products. The least productivity was observed in a crop rotation with cereals (5.88 t/ha), where the main products made up only 33%. Nitrogen concentration fluctuations in drainage water depended on the season of the year, the onset and the end of the runoff. During the rotation period N concentrations were partly predetermined by grown crops only in a classical crop rotation (field I) and in a 100% cereal crop rotation (field III). In all the rest fields they correlated with nitrogen amount inserted with fertilizers and plant residuals (R2 was 0.814 and 0.521 respectively) and depended on mineral nitrogen amount contained in the soil in spring. Twice as large nitrogen amounts were leached in a crop rotation field 50% of which was occupied by hoeing crops and in a 100% cereal crop rotation field to compare with a classical crop rotation (field I) and perennial grass (field IV). No major differences between leached amounts of phosphorus were determined, except for its increased concentrations and leaching in cereal crop rotation, cereal + pulse crop rotation and perennial grass field. Meanwhile, the leached amounts of potassium were relatively larger. Increasing yields predetermined the reduction in NPK leaching. Keywords: crop rotation, yield, nitrogen, phosphorus, potassium, drainage water, runoff.
Article received 04 2002, given to print 07 2002.
THE Implementation and Investigations of THE Functioning of Macrophyte BiofilterAusrys BALEVICIUSSummaryThe macrophyte biofilter as a terminal stage of wastewater treatment was created and implemented into two basins of wastewater treatment plant of Skersabaliai carriage washing station in summer 1996. The main purpose of this reed (Phragmites australis) - based macrophyte biofilter was to clean microbiologically pre-treated water, rich in organic matter, nitrogen and phosphorus, so as to satisfy the requirements for discharge to natural water bodies. The state of artificial hydroecosystem of biofilter was investigated during the periods 1996-1998 and 2000-2001. The hydrochemical conditions varied greatly in macrophyte biofilter during the research. In winter 1996-1997, the macrophyte biofilter was even destroyed by an unauthorized direct inlet of unpretreated wastewater (BOD7 reached 736-1050 mg O2/l in June 1997). Biofilter basins were cleaned in summer 1997, and the ecosystem of the biofilter was redeveloped. Since summer 1997, the quality of inlet water was strictly controlled and hydrochemical conditions became more stable and suitable for biofilter functioning. This resulted in a greater number of species (31 species of phytoplankton algae and 24 species of zooplankton were identified) and more rapid water purification (decomposition of organic matter and incorporation of biogenous and other elements into the macrophyte biomass). The investigation showed that during the processes of destruction of organic matter and respiration about 8.8 kg of organic carbon were removed from each basin of the macrophyte biofilter. Algal blooms, which are undesirable in the macrophyte biofilter due to high production of unmanageable autochtonous organic matter, were taken under control using duckweed (Lemna sp.) that covered the surface of both basins and shaded the phytoplankton. Macrophyte biomass, which was about 80 kg (dw), contained about 3% of N and 0.22% of P, i.e. about 2.3 kg of nitrogen and about 290 g of phosphorus were removed from the biofilter in late autumn 1997. The amounts of removed biogenous materials may be ten times larger because of a very intensive growth of macrophytes in 2000 & 2001. 6680 m3 of sewage were treated during the vegetation season in 2001. Periodical inlet of 40-400 m3 of pre-treated sewage containing 73-89 mgO2/l BDS7; 34-655 mgO2/l ChDSCr; 18,4-97,9 mgO2/l ChDSMn; 1,13-34,4 mg/l total N; 0,4-18,5 mg/l total P was performed from May to October 2001. After 2-6 weeks various forms of organic material decreased by 20 - 80% (according to BDS and ChDS). Up to 90% of total N and 96% of total P were removed. Investigations in 2000-2001 showed no extreme hydrochemical conditions and much greater stability of the structural and functional ecosystem parameters, so the water quality entering the macrophyte biofilter was satisfactory for surviving of organisms and water cleaning activities. Nevertheless, it is necessary not to overload the biofilter with hardly destructable organic matter, which consume large amount of dissolved oxygen and may render the ecosystem unstable or even kill some of its biotic components. Keywords: macrophyte biofilter, sewage treatment, artificial hydroecosystem, structure, functioning.
Article received 02 2002 02, given to print 07 2002.
INVESTIGATIONS ON MUSES LAKE SAPROPEL EFFICIENCY IN CROP ROTATIONSEugenija bakSiEnESummaryThe investigations on the efficiency of siliceous sapropel and its mixture with manure in crop rotation with soddy-podzolic sandy loam soil was carried out in Voke Branch of the Lithuanian Institute of Agriculture in 1994-1999. The results of the investigation showed that 50 and 100 t/ha rates of applied siliceous sapropel and manure increased the yield of crop rotation by 45-47 % and 27 % respectively. Soil fertilization with siliceous sapropel made no effect on soil reaction indices. Only a bigger rate of sapropel (100 t/ha) increased the content of total nitrogen and humus in the soil. Applied mineral fertilizers compensated the amounts of mobile phosphorus and potassium that are necessary for plants to grow. The application of sapropel had positive influence on physical properties of soddy-podzolic sandy loam soil. The siliceous sapropel increased the humidity and porosity, and decreased the density of soil more than manure and mineral fertilizer. Keywords: sapropel, manure, yield, soil, properties.
Article received 04 2002, given to print 07 2002.
METHODS OF MATHEMATICAL MODELLING OF FLOOD FLOWSSaulius VAIKASASSummaryThe paper deals with the questions of the application of mathematical modelling in different scientific researches and also presents the analysis of mathematical model schemes. There are presented the applications of Saint-Venant and other differential equations for the hydraulic calculations of flood flows in the valley. It is noticeable that conventional topological schemes of 2-dimensional flow are most suitable under the conditions of flood flows entering the valley and others. The application of the existing different hydraulic programs for scientific researches is often limited by restricted universal formulas and schemes used in those researches, Therefore, on the basis of my individual experience considering hydraulic modeling, I recommend taking advantage of the benefits of hybrid modelling method. The paper also presents the examples of hydraulic modelling of the Nemunas delta and the Mekongas delta. Keywords: mathematical modelling, equation – based solution, flood flows.
Article received 04 2002, given to print 07 2002.
INVESTIGATIONS ON THE EFFICIENCY OF ANAEROBIC WASTEWATER TREATMENT IN SETTLEMENTS OF LITHUANIAMidona DAPKIENE, Rene KUSTIENESummaryAnaerobic treatment is one of the oldest wastewater treatment technologies. Nowadays anaerobic treatment methods are widely put into world practice. In Lithuania this technology was started being applied only ten years ago. This article deals with the conditions of fifteen anaerobic wastewater treatment plants in Lithuania. It was determined that the pollution according to BOD7 and suspended solids periodically exceeded the permissible rate in four wastewater treatment plants. The treatment efficiency of six such plants was good, five of them worked ineffectively. Hydraulic and organic overload, low temperature of wastewater and technological drawbacks predetermine the insufficient quality of treatment process. The reason causing low treatment efficiency of anaerobic digesters was the uneven distribution of wastewater in a reservoir. It was revealed that the exploitation of anaerobic digesters of wastewater treatment plants was insufficient. An inadequate maintenance influences the functionality of anaerobic wastewater treatment plants. The means for the solution of this problem are proposed in the article. Keywords: three-level continuous secondary treatment, anaerobic treatment, functioning efficiency, anaerobic digester ANBIO, volume usage.
Article received 04 2002, given to print 07 2002.
METHODS AND MEANS FOR TRASH COLLECTION AND REMOVAL FROM KAUNAS RESERVOIRZenonas RIMKUS, Bronislovas RUPLYSSummaryThe main purpose of the article is to reveal a problem dealing with the formation conditions of trash in the Kaunas reservoir, on the basis of the study of normative and other literature to propose for designers some generalized ideas about how to collect and remove the trash that gathers at Kaunas HEPP. The trash (frazil ice, wood, floating civilization waste etc.) is a significant problem of the maintenance of any hydroscheme, especially in cases of rather big water flow velocities upstream of hydroschemes and/or prolonged sludge periods. Due to small headwater flow velocities, frazil ice problems are relatively simple at Kaunas hydroscheme (the ice cover forms quickly). In latter years a problem of the material trash became important – functionaries of the environment protection insist on Kaunas HEPP holding, collecting, and utilizing trash from the headwater . In the context of world experience the requirements of the environment protection functionaries are under discussion because 1) prevention and treatment of material trash is often ascribed to the owner (joint owner) of the reservoir created by a hydroscheme and 2) bigger part of trash is proposed to be passed through a hydroscheme, as the trash is an important component of ecological diversity of a watercourse: only the trash dangerous for the environment is required to be withheld and treated separately (filled with some material or empty vessels, bottles, plastics, various artificial materials, tires, corpses etc). Analysis of trash retention shows that most experience is gained when solving the problems of sludge retention and others. The system of methods and means comprises various floating barriers for trash retention and its direction into the zones of its passage (taking out, stationary barrier walls, trashrack cleaning equipment.). Keywords: hydroelectric power plant (HEPP), water reservoir, (floating) trash, barrier.
Article received 05 2002, given to print 07 2002.
TECHNOLOGICAL INVESTIGATIONS OF MANURE SPREADING MEANSAlbertas STEPONAVICIUSSummaryIn this paper the main kinds of manure are discussed, the value of manure as a fertilizer, as well as its impact upon environment depending on its storage and usage time are analyzed. In this article the analysis of manure spreading mechanisms and the main indices of the work are presented. On the basis of the investigations it has been established that in order to spread solid manure on the top of the soil it is expedient to use manure spreading machines with vertical spreading apparatus, such as the ones produced by the Danish company IF–Fabriken. While investigating a slurry spreading machine SMS – 6 created at the Institute it appeared to be expedient to create its new construction. In this article the results of investigation and agrotechnical estimation of manure spreading machines SMS – 9 and SMS – 12 created at the Institute are presented. Keywords: manure, manure spreading machines, spreading evenness.
Article received 03 2002, given to print 07 2002.
THE OPTIMIZATION OF LAND USE IN FARMS IN CENTRAL LITHUANIAVirginija GURSKIENE Summary Within the period of land reform farming forms changed, many new small farms were established and big agricultural enterprises were reorganized in Lithuania. Land management works should secure a more effective agricultural production. The properly planned land use should guarantee secure the necessary level of agricultural production, protection of soils, ecological stability of the territory and the improvement of farming lands. After the investigations and their analysis, the following outcomes were formulated: 1. Results of the optimization of farms in Central Lithuania: - it has been determined that the farms of corn and sugar beet are most profitable; corn and potatoes, corn and rape and corn farms are following in accordance to the profitability; - the analysed farms are arranged in the following order only in corn and sugar beet group in accordance to the profitability: 100 ha (most profitable), 50 ha and 30 ha; - the most profitable crop alternation from several analysed crop alternations with corn, the rotation members including peas, winter wheat and sugar beet, were determined; - the farms with plant-growing specialization (where cattle is kept) are arranged in the following order in accordance to the profitability: - corn: 30 ha (most profitable), 50 ha, 100 ha; - corn and potatoes: 30 ha, 50 ha and 100 ha; - corn and sugar beet: 100 ha, 50 ha and 30 ha. 2. Rational usage of agricultural land is to be assured by the effective system of territory planning and land management based on the principles of hierarchy. 3. All factors should be evaluated in a complex way while preparing land management projects, economic-mathematical methods are to be applied for the determination of the purpose of farming and optimal size of stocks. Keywords: farms, economic-mathematical methods.
Article received 02 2002, given to print 07 2002.
LOCALIZATION OF PROPER NAMES OF WATER FLOWS AND RESERVOIRS IN CARTOGRAPHIC MAPSViktoras LUKOSEVICIUS, Romualdas GIRKUS SummaryThe article deals with the usage and standartization of the names of Lithuanian water bodies (rivers, lakes and streamlets) since 1920 up to now. There are presented original documents illustrating the careful attitude of Lithuanian intellectuals, scientists prof. S.Kolupaila, prof. Z.Ivinskis, prof. P.Bucys and orhers to the hydronyms. In the paper there are also discussed the problems of the usage of hydronyms in the preparation of official cartographic publications. It is stated that at present ( in comparison with the pre-war period) the attention of the experts payed to the hydronyms has been reduced. However,the neccessity for the arrangement of proper names of Lithuanian water bodies has increased. Inaccuracity is detected in the new Classification of Lithuanian Republic Rivers and Reservoirs in the terms of localization and spelling of hydronyms. The decisions of Lithuanian Government support an improper usage of Lithuanian hydronyms. For this reason it is recommended to prepare another dictionary of Lithuanian hydronyms which would have not only scientific but practical value as well. Keywords: hydrography, names, hydronyms, topographic maps.
Article received 04 2002, given to print 07 2002.
INVESTIGATIONS OF FREEZE AND SALTS INFLUENCE ON CONCRETE WITH MICROSILICA ADDITIVESVincas GURSKISSummaryThe resistance of superficial layer of concrete, while influenced by cyclical freezing-thawing and NaCl salt, has been analyzed in this paper. The research has been carried out by 2 methods. According to the I st method, dry salt is poured over the icy surface of samples, and according to the 2 nd one concentrated saline solution is poured over it. An adequate amount of these materials is poured over in order 5% of NaCl solution would form after the ice thawing. The damage of concrete is evaluated according to the change of sample mass, the depth of erosion of superficial layer as well as the change of aerial permeability. While investigating concrete samples of 7 compositions, the efficiency of superplasticizer and 3-typed active mineral additive of microsilica has been evaluated. It has been established that concrete with 10% of microsilica in them are more resistant than those containing 20% of this additive. More dispersive and having more amorphous additive SiO2 positively influences the resistance of concrete surface, while influenced by cyclical freezing-thawing and salt. It has been established that the erosion of concrete surface is going faster when the salt is poured over the concrete covered with thin ice to compare with concentrated saline solution poured over it. Therefore, the pouring of the salt should be foreseen in order to quicken the researches of freeze resistance and salt influence on a concrete surface, as well as concrete surfaces should be watered (sprayed) with concentrated saline solution while fighting with naked ice during the exploitation of concrete coating. Keywords: concrete, freeze resistance, ice thawing salts, microsilica.
Article received 04 2002, given to print 07 2002.
Calculation of Bearing Elements Based on Theories of StrengthKazys Sleževičius, Jonas RoliCius, Feliksas Mikuckis SummaryConcentration of straining under long duration load together with other effects influences the strength of material and the character of failure. Failures of fragile materials have been analysed theoretically and experimentally. The developed model of bearing elements calculation is based on the theories of strength. Considerable vertical direct straining occurs below the platform under load. The material thickens forming a destructive cone which splits the bearing element into sectional elevations. The adjacent material forms a contraction around the destructive cone, and increases the ultimate compression of concrete fractures, when maximum tensile stress reaches limiting values of concrete strength. The functional values of the coefficient to calculate local compression of fragile materials are presented. They are based on theoretical calculations and coincide with experimental data. The values include dimensions of the element as well as physical and chemical properties of the material and its crushing, tensile and torsion strength. Dimensions of concrete casings enable us to evaluate the strength of bearing material and to work out reinforcement placement, taking strength of material into consideration. Keywords: crushing, concrete, failure hypotheses, state of stress, fragile materials.
Article received 02 2002, given to print 07 2002.
THE nutrient losses AND The yield of crops on THE hilly land of Eastern LithuaniaOna BUNDINIENESummaryThe experiment was conducted in soddy-podzolic slightly and moderately podzolized slightly and moderately eroded loam soil. The soil was poor in humus (1.8% by Tiurin) and rich enough in phosphorus and potassium (244 and 188 mg kg-1 by A-L respectively). Different usage of soil management has been investigated during this experiment: three farming sistems (organic-biological, integrated and intensive) in the field crop rotation and two others (organic-biological and intensive) when growing perennial legumine-spiked grass and lying permanent fallow. At the foot of each research plots reservoirs were installed to collect soil and run-off water. The data of field experiment showed that the fallow and perennial grass protected hilly soils fom erosion very efficiently. Here the losses of soil were the least (0.003 t ha-1yr-1) and the losses of nutrients occurred only with flowing water and in organic-biological farming system their amount in kg ha-1per year were obtained as follows: nitrogen – 0.9, phosphorus – 0.1, potassium – 0.4, calcium – 1,6 and magnesium 0.4. Grass produced rich yield (on the average 61.0 GJ ha-1 per year). Due to the applied mineral fertilizers this yield increased up to 73.7 GJ ha-1 per year, and nutrients losses were smaller. The crops of field crop rotation growing without any mineral fertilizers produced the yield which was on the average twice as low as the one obtained from perennial grass. The yield of crops when mineral fertilizers were applied was bigger by 50 - 60%, but still it was lower by 21 - 46% than the yield obtained from grass growing in the same systems. Soil losses in field crop rotation in organic-biological farming system reached 2.3 t ha-1 yr-1 and nutrient losses were obtained 4.4, 0.6, 1.5, 1.6 and 0.4 kg ha-1yr-1 accordingly, the applied mineral fertilizers decreased the losses of nutrients both in field crop rotation and in grass fields. The nutrient losses were smaller in permanent fallow: nitrogen – 0.1. phosphorus – 0.01. potassium – 0.1. calcium – 0.1 and magnesium – 0.2 kg ha-1yr-1 . Keywords: crop rotation, farming trend , nutrient losses, flowing water.
Article received 03 2002, given to print 07 2002. |
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