Influence of selenium fertilization on soil selenium status
Yli-Halla, Markku (2005)
Yli-Halla, Markku
Julkaisusarja
Agrifood Research ReportsMaa- ja elintarviketalous
Numero
69
Sivut
s. 25-32
MTT
2005
Tiivistelmä
Selenium (Se) has been applied to Finnish agricultural soils in mineral fertilizers as sodium selenate since 1985. Usually, less than 10% of applied Se is taken up by the crop. Previous studies indicate that the level of easily soluble (hot water extractable) Se has not been elevated during the period of Se fertilization. It is assumed that Se not taken up by the crop is mostly retained by the acidic soil. In this study, Se balance over the period of 13 years (1992- 2004) was calculated on the basis of crops grown and fertilizers used in 48 fields of 10 research stations at different parts of Finland. The material consisted of 10 organogenic soils, 18 coarse mineral soils and 20 clay and silt soils. The pH(H2O) of the soils was 4.6 6.9 (mean 5.9). The soil samples taken from these fields in 1992 and 2004 were analysed for aqua regia (AR) extractable Se, which indicates the semi-total Se concentration. These results were also converted to grams per hectare by multiplying the AR extractable results with the volume weight of the soil in order to compare them with the Se balance of the respective fields. The cumulative Se application was on average 37 g/ha (range 3 78 g/ha) during the 13-year period. Highest applications took place in intensive grassland cultivation. Se applications resulted in the estimated balance of 31 g Se/ha (range 2 67 g/ha). The average concentrations of AR extractable Se in the samples taken in 1992 were 0.393 mg/kg in organogenic soils, 0.148 mg/kg in coarse mineral soils and 0.211 mg/kg in clay and silt soils. These results corresponded to 516, 363 and 470 g/ha in the three soil groups, respectively. According to soil analyses, the Se content of a 23-cm deep plough layer was on average 23 g/ha higher in 2004 but the difference was not statistically significant. It was concluded that the possible accumulation of Se in soil occurring during the 13-year period was masked by the heterogeneity of the sampled fields and could not yet be detected by soil analyses. The balance, calculated from fertilizer use and estimated crop uptake, corresponded to 8% (range 0.7 22%) of the Se content of the plough layer.
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