AGRONOMIJAS VĒSTIS - Latvijas Lauksaimniecības universitāte

AGRONOMIJAS VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 2008pH ±S Se, mg kg -1 n K O, pH Se, mg kg -1 n K O, pH Se, mg kg -1Table 2. Selenium concentration dependence on the potassium content in soil, ±sSand and sandy loam Light loam Medium, clay loam and claypH 6,019 83±11 6,8±0,5 0,152±0,078 15 88±11 7,1±0,4 0,160±0,051 7 89±7 7,1±0,4 0,152±0,028105 145±29 6,9±0,5 0,151±0,047 121 147±28 7,2±0,5 0,159±0,066 53 148±26 7,2±0,5 0,212±0,05119 210±98 6,8±0,4 0,145±0,045 22 269±55 7,0±0,50 0,159±0,053 32 350±417 7,1±0,5 0,222±0,070DiscussionThe annual precipitation rate in separate Lithuanian regions is different. This influences thevolumes of selenium brought to the soil by rais-fall and leached into deeper soil layers. Thecalculation of selenium concentration the relation to the average annual precipitation rate revealeda trend: selenium concentration is higher in regions with a higher annual precipitation rate, andwhere the average annual precipitation rate is more than 750 mm, selenium concentration in soiltends to decrease (Figure 1). There is a positive correlation between the selenium concentration insoil and higher regional average annual temperature; it can be expressed by the linear equation withR=0,28.Higher air temperature increases water evaporation from the soil and decreases the amountof water getting into the deeper soil layers. We assume that less selenium is leached in theseregions. There is no data available on the amounts of selenium deposited in the soil byprecipitation. According to the average calculations for the whole planet, annual precipitationbrings about 400 µg selenium per 1 m 2 , and about 310 µg of selenium is released from the soil intothe atmosphere (Haygart at all., 1993). Thus precipitation deposited selenium accumulation in soilis possible in zones, where selenium concentration in fall is higher.The mineral fertilisation effect was a trend of selenium concentration increase. Seleniumconcentration increase was highest in plots fertilised with the full NPK fertiliser complex. Otherresearchers have also noticed the technogenic accumulation of selenium caused by the applicationof phosphorus and potassium fertilisers. Nakamuru (2006), after having conducted someexperiments in Japan, states that phosphate fertilisation decreases the sorption of selenium by thesoil. Thus selenium might be leached into deeper layers. We assume that the opposite effect ofphosphorus fertilisers was hidden by the in interaction with other fertilisers. On the other hand,selenium deficiency is observed in Europe despite the fact that selenium concentration in motherrock is sufficient (Ermakov, 1992). Borovska (2000) noticed, that significant seleniumconcentration increase in 5-35 cm soil layer is observed after organic fertilisation.Significantly higher selenium concentrations were determined in two types of soils,containing larger amounts of plant available potassium: light texture, pH 5,1-6,0 and heavy texture,pH higher than 6,0. This finding matches the testing results of soil samples taken from long-termfertilisation experiments – more selenium was found in the soils of NPK fertilised plots. The resultof data processing incorporating all soil types is the following equation, expressing a relationbetween selenium concentration increase and potassium content increase in the soil: Se mg kg -1 =0,133+0,0002*K 2 Omg kg -1 , R=0,22. the correlation was better for all types of soil at pH 5,0-6,0:Se mg kg -1 =0,111+0,0004 K 2 O mg kg -1 , R=0,33. the selenium concentration difference was 0,092mg kg -1 when the soil richness in potassium values 70 mg kg -1 and 300 mg kg -1 were compared.The strongest correlation between selenium concentration and potassium content wascalculated for clay loam and clay at pH 5,1-6,0: Se mg kg -1 = 0,1221+0,0005*K 2 O mg kg -1 ,23