Waste silicate minerals as potassium sources: a greenhouse study on spring barley

Abstract

After 1989, the use of potassium (K) mineral fertilizers in the Czech Republic dropped from ∼55 kg K ha⁻¹ to a mean rate of ∼6.5 kg in the last decade. In order to test alternative solutions for K fertilization, the trioctahedral mica mineral zinnwaldite (8% K), orthoclase (10% K) and waste mica from Cínovec (Krušné Hory Mts/Erzgebirge, Czech Republic), consisting primarily of zinnwaldite, were applied as the only K sources for spring barley. The minerals were treated in three different types of high-energy mills under different working conditions. Application rates in the range 139–820 mg K kg⁻¹ were tested in quartz sand cultures. In all treatments, plant growth, total plant biomass and the K content in the plant tissues increased in the order zinnwaldite > waste mica > orthoclase. K fractionation and K plant uptake were significantly influenced by the milling method used. The effect of 195 mg K kg⁻¹ as zinnwaldite on K uptake from K-depleted soils was positive; however, it was smaller than in sand cultures because of the relatively high content of non-exchangeable K in the soils. Direct use of waste mica as a K fertilizer is limited by the increased fluorine and heavy metal content.

Keywords:

• potassium
• fertilizers
• waste processing
• silicate minerals
• high-energy milling

Acknowledgements

This study was supported by the Ministry of Agriculture of the Czech Republic, Project No. QI91C118. The authors are grateful to Ilja Knésl for performing the mineral analyses; to Marie Trčková for help in designing the sand culture experiments, and to two anonymous referees for their valuable comments on the manuscript.