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<strong>AGRONOMIJAS</strong> VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 2008almost did not change or tended to decrease, while in phosphorus and potassium poor soils –increased. Application of 60 t ha -1 of manure once per crop rotation cycle resulted in almost perfectphosphorus balance even in soils of plots not fertilised with potassium fertilisers; as for potassium– the balance was negative when the crop was not fertilised with potassium fertilisers.After application of average NPK rates and ploughing-in of winter wheat straw phosphorusbalance in soil was positive, as for nitrogen and potassium balances – the negativity was onlypartially compensated.ConclusionsThe best nitrogen balance (close to 0) was achieved when nitrogen fertilisation rates wereadjusted according to the mineral nitrogen content in soil in spring.When 60 t ha -1 of manure were applied once per crop rotation cycle, negative nitrogenbalance was calculated only for the plots not fertilised with nitrogen fertilisers.Nitrogen balance was negative when crops were not fertilised with manure and receivedaverage mineral fertilisation rates or the rates calculated using balance method, also in the casewhere winter wheat straw was ploughed-in once per crop rotation cycle.In spring mineral nitrogen content in soils of plots fertilised with different nitrogenfertilisation rates was quite similar. Mineral nitrogen content depended mainly on precipitation (0-40 and 0-60 cm – R = 0.66 and 0.71)and somewhat less on air temperature ( R = 0.41- 0.45).Fertilisation efficiency in soils rich in nutrients is low, and the excess of nutrients can beleached from soil into environment.In order to decrease the risk of environment pollution, the best solution is application ofaverage phosphorus and potassium fertilisation rates adjusted according to the soil agrochemicalproperties and calculated using the balance method. When crops were fertilised with the ratescalculated using the aforementioned methods, content of these nutrients in soil with higher amountof phosphorus and potassium almost did not change or tended to decrease, while in soils with loweramount of phosphorus and potassium content of this elements increased.References1. Aoalsteinsson S., Jensen P. (1990) Influence of temperature on root development and phosphate influxin winter wheat grown at different P levels, Physiologia plantarum, 80, 69–74.2. Bartashevich V.I. (1987) Straw as fertiliser and crop productivity on reclamated soils. Cropproductivity improvement methods, 18. 90-95.3. Becker F.A., Aufhammer W. (1982) Nitrogen fertilization and methods and predicting the Nrequirments of winter wheat in the Federal Republic of Germany. Symposium on fertilizers and intensiveproduction in the EEC, London, 35–65.4. Bogdevich I.M. (1981) Scientific basis for fertilisation in western region of USSR, Minsk, Belorussia,–200.5. Goulding K.W.T., Poulton P.R., Webster C.P., Howe M.T. (2000) Nitrate leaching in the BroadbalkWheat Experiment, Rothamsted, UK, as influenced by fertilizer and manure input and the weather. SoilUse and Management, 16. 244-250.6. Greenwood D.J, T.V. Karpinets. (1997) Dynamic model for the effect of K-fertilizer on crop growth,K-uptake and soil – K in arable cropping. Field test of the model. Soil Use and Management, 13, 184–189.7. Kulakovskaja T.N. (1974) Soil-agrochemical basis for achievement of high yields, Minsk, Belorussia,393–397.8. Lazauskas S., Vaisvila Z., Matusevicius K., Pliupelyte E. (1996) Nitrogen fertilisers‘ efficiency forbarley crop as affected by mineral nitrogen amount in soil. Agriculture, Dotnuva-Akademija, 50, 41–53.9. Mattson L. (1990) Effect of the inorganic soil nitrogen level on fertilizer nitrogen requirements byspring barley grown on regularly manured soils. Swedish J. Agric. Res., 141–145.10. Mazvila J., Vaisvila Z., Masauskas V. (1996) Plant available phosphorus and potassium amount inLithuanian soils and its impact on yield of agricultural crops. Agricultural Science, 2, 21–29.11. Mengel K. (1984) Nutrient availability, fertilizer input and agricultural yields. Proc. 18th. Colloq.Intern. Potash Inst. Nutrient Balance and fertilizer needs in temperate agriculture, -Gardone-Riviera, Italy,1984. 349–360.12. Mezals G. (1997) Modelling of humus amount in the main types of Latvian soils. Scientificconference in commemoration of 40 th anniversary of Lithuanian soil researchers society. Papers. Kaunas,96–100.64
<strong>AGRONOMIJAS</strong> VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 200813. Neeteson, J.J, Greenwood D.J., Draycott A. (1988) A dynamic model to predict yield and optimumnitrogen fertilizer application rate for potatoes. In Nitrogen Efficiency in Agricultural Soils, eds JenkinsonD.S. and Smith K.A., Barking, United Kingdom, Elsevier, 384–393.14. Pliupelyte E., Lazauskas S., Vaisvila Z., Matusevicius K. (1995) Winter crop yield as affected bymineral nitrogen amount in soil and nitrogen fertilisation rates. Agriculture, 44, 143–153.15. Shiel R.S., Mohamed S.B., Evens E.J. (1997) Planning phosphorus and potassium fertilization of fieldwith varying nutrient amount and yield potential. Precision agriculture’97. Spatial Bios ScientificPublishers, 1, 171–178.16. Svedas A., Tarakanovas P. (2000) Fertilisation planning. Computer version ‘Fertilisation’, Akademija.-34.17. Tripolskaja L., Greimas G. (1998) Changes of plough horizon soil agrochemical properties caused bydifferent fertilisation systems. Agriculture, Dotnuva-Akademija, 63, 55–69.18. Vaisvila Z. (1996) Role of plant available nitrogen, phosphorus and potassium in agricultural cropsnutrition. Habilitation work, Dotnuva-Akademija, 56-97.DATU STATISTISKO APSTRĀDES METOŽU PIELIETOŠANAS IESPĒJASNEZĀěAINĪBAS IZPĒTĒSTATISTICAL METHODS FOR ANALYSING THE DATA OF WEED FLORAPiliksere D.State Priekuli Plant Breeding Institute, Zinatnes St. 1a, Priekuli, Cesis Distr., Latvia, LV-4126phone: +371 64130162, fax: +371 4107217, e-mail: DacePil@e-no.lvAbstractThe ecological approach to the agriculture supports a conservation of biodiversity in agroecosystems.The biodiversity is a part of a well-balanced organic system and thereby ensures morestable yields of the crop. The diversity of vegetation within and around agro-ecosystem is animportant component of biodiversity. Natural plants provide many animal species with a habitatand food resources. Therefore it is important to investigate the diversity of weed and their impacton ecological processes in crop fields, as well as on amount and quality of the yield. It is possibleto use the same statistical methods for analyzing vegetation diversity of weed flora as inphytosociology. The methods, mentioned in this paper, have been used in agriculture only for lasttwo decades in Europe. There are no similar investigations in Latvia. TURBOVEG is acomprehensive database management system designed for the storage, selection, and export ofvegetation data – among them also weeds. Indicator values of Ellenberg characterize the ecologicaloptimum of plants concerning climatic and edaphic factors. Two-way indicator species analysisTWINSPAN and software JUICE can be used for the classification of weed flora. Direct andindirect ordination – CCA and DCA – can be used to find the main ecological factors thatdetermine the variation in the data set. SPSS is now widely used in nature sciences and includesmany possibilities of data analysis. MS Excel is suitable for analyzing small amount of data.Different statistical methods are characterised for analyzing vegetation data to determine theiradvisability for investigations of the diversity of flora in agriculture. To compare the results, usingthese methods it is useful for research of weeds in the fields of both systems of agriculture –organic and conventional.Key wordsWeed flora, statistical methods, organic agricultureIevadsEkoloăiskā pieeja lauksaimniecībā atbalsta bioloăiskās daudzveidības saglabāšanuagroekosistēmās. Tā kā bioloăiskā daudzveidība ir daĜa no labi līdzsvarotas organiskās sistēmas,kas, darbojoties saskaĦā ar dabas procesiem, ir noturīgāka pret slimībām, tā nodrošina stabilākulaukaugu ražu. Veăetācijas daudzveidība ir nozīmīga agroekosistēmas un to ietverošās videsbioloăiskās daudzveidības komponente. Zviedrijā vairākas apdraudētas un retas sugas tika65
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