Selenium-containing fertilizers

Selenium content in soils

Large-scale mapping of selenium content in soils, waters, and plants has been carried out in European and Asian countries, and attempts are being made to regulate selenium content in human food products and animal diets. In Russia, extensive biogeochemical areas with varying degrees of selenium deficiency have been identified in the Non-Chernozem Zone, the Southern Urals, and Transbaikalia. A biogeochemical province with excess selenium was found in the Uyug and Baryk valleys of Tuva.

An agroecological survey of regions in the Non-Chernozem Zone of the European part of the country showed a low selenium content — 61–729 µg/kg. The lowest amounts, up to 169 µg/kg, are characteristic of podzolic and sod-podzolic soils, as well as soils on sandy soil-forming rocks. Maximum selenium concentrations — from 521 to 727 µg/kg — were found in peaty, gleyed soils enriched with iron oxides and formed on carbonate rocks. In most cases, soils contain up to 400 µg Se/kg soil, which is classified as deficient content.

In soil, there are complex relationships between selenium and other elements of mineral plant nutrition. For example, application of cobalt, zinc, and nickel enhances the microbiological formation of volatile selenium compounds, boron and manganese do not affect these processes, while molybdenum, mercury, chromium, and lead inhibit the transformation of selenium compounds into volatile forms.

For several years, research has been conducted in the trace element laboratory of the MAA on growing agricultural products enriched with selenium. In a series of experiments, the effect of applied sodium biselenite on yield, its quality, and selenium content in vegetable crops, wheat, rapeseed, and lupine was studied.

The studied vegetable crops without selenium application accumulated it in small amounts — 56–303 mg/kg dry matter. The application of sodium biselenite in increasing amounts from 25 to 500 µg Se/kg soil led to an increase in content in dill plants by a factor of 2.5–15.7, in radish root crops by a factor of 4, in parsley roots by a factor of 2.4–3.8 and by a factor of 3.5–10.0 in the aboveground part. With an increase in the dose of sodium biselenite from 50 to 1000 µg Se/kg soil, the content in leaf lettuce increased by a factor of 10, in spring garlic by a factor of 3.7–16.0, in the green mass of yellow lupine by a factor of 3–11 and by a factor of 6–25 in grain. Foliar feeding of yellow lupine with 0.0005% and 0.002% sodium biselenite solution in field experiments increased the content in green mass by a factor of 4–9 and in grain by a factor of 4–8.

Thus, under the experimental conditions on sod-podzolic soils, the application of selenium at doses of 25–1000 µg/kg soil makes it possible, without reducing yield, to substantially enrich agricultural products with selenium. Among the crops tested, garlic proved to be the most pronounced accumulator.

In world practice, selenates and selenites are used as selenium-containing fertilizers for foliar feeding and seed treatment. The most effective and widely used method is the application of selenium to the soil together with macronutrient fertilizers.

References

1. Mineev V. G., Sychev V. G., Gamzikov G. P. et al. (2017). Agrochemistry. Textbook. Ed. by Mineev V. G. Moscow: Publishing House of the D. N. Pryanishnikov All-Russian Research Institute of Agrochemistry (VNIIA).
2. Yagodin B. A., Zhukov Yu. P., Kobzarenko V. I. (2002). Agrochemistry. Ed. by B. A. Yagodin. Moscow: Kolos.