AGRONOMIJAS VĒSTIS - Latvijas Lauksaimniecības universitāte

AGRONOMIJAS VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 2008MethodsSoil sampling was conducted taking into consideration soil texture, acidity, location, soiltaming degree (concentration of plant available phosphorus and potassium). The grouping oftesting results was based on these characteristics. Soil samples were taken from the plough layer infields of long-lasting (30 years) fertilisation experiment in Sk÷miai (light loam sandy soil,Combisol, CMg-n-w-cap) and 8 years-long fertilisation experiment in Kriūkai (silty loam brownsoil). Soil sampling was conducted in accordance with the requirements of standard ISO-10381.Soil samples were brought to air-dry condition by drying at +30 0 C with active ventilation (ISO-11464).Selenium was extracted by boiling the soil sample in concentrated HNO 3 in closed system for 2hours. Soil and acid ratio 1:10. After boiling the solution was diluted with analytical water.Determination of selenium in extraction was conducted using atomic absorption spectrometry withgraphite furnace (Aanalyst 800), EDL lamp. Wave length 193,7 nanomicrons, atomisingtemperature 1900 0 C. Palladium and magnesium nitrate were used as modifiers for the eliminationof systemic errors originating from matrix interferences (Huang, Fujii, 1996).The amount of plant available phosphorus and potassium in the soil were determined using theEgner-Riehm-Domingo method (Egner, Riehm, Domingo, 1960). pH value was determined in 1 MKCl suspension, soil and solution ratio 1:2,5 (ISO-10390). The average annual temperature andprecipitation data was taken from regional meteorological stations. Mean standard deviation (s) ispresented in tables and the text, sx - standard error of the mean. The correlative regressive relationwas calculated using the “Statistica” programme.ResultsSoil secondary reference substances of different properties were used in the seleniumconcentration determination process in order to ensure the testing quality. The preparation of thesesecondary reference substances was based on comparisons to the standard samples (CRM 2709 andCRM PL-1). Relative indefinition was less when selenium concentration in the soil was higher. Thedistribution of soils according to selenium concentration in Lithuanian regions was different (Table1).Table 1. Selenium content in soils of different Lithuanian regionsCountyAverageGroup Se mg kg -1 , %Se, mg kg -1 n 0,3Alytus 0,129±0,052 22 23 63 14 0Kaunas 0,161±0,088 85 33 40 18 9Klaip÷da 0,176±0,056 150 3 69 22 5Telšiai 0,177±0,060 23 0 61 35 4Šiauliai 0,147±0,049 66 8 77 14 2Utena 0,180±0,062 31 3 61 32 3Panev÷žys 0,166±0,065 102 9 64 22 6Taurag÷ 0,174±0,037 65 6 72 22 0Marijampol÷ 0,176±0,078 134 22 36 37 5Vilnius 0,157±0,041 50 8 80 12 0The highest average selenium concentration was found in Utena, Telšiai, Marijampol÷,Klaip÷da and Taurag÷ counties, the lowest – in Alytus, Šiauliai and Vilnius counties. Seleniumconcentration diversity in separate counties is different. The largest share of soils with seleniumconcentration higher than 0,200 mg kg -1 was in Marijampol÷ (42 %), Telšiai (39%), Utena (35 %)counties, and the smallest - Vilnius (12%), Alytus (14%) and Šiauliai (16%) counties. The share ofsoils with very low selenium concentration (less than 0,100 mg kg -1 ) was relatively the largest inKaunas (33%), Marijampol÷ (29%) and Alytus counties.The annual precipitation rate in separate Lithuanian regions is different (Figure 1). Therelation of selenium concentration in the soil under the influence of annual air temperature isstronger than with precipitation. Selenium concentration is higher in the regions with higheraverage annual temperature (Figure 1).21