Diagnostics of soil potassium status in the forest-steppe of West Siberia

Abstract

The aim of the study was to review indicators and propose grades of soil potassium availability to crops.. The need of assessing soil potassium status on the basis of combined use of several diagnostic indicators, characterizing soil potassium pool, both quantitative and qualitative, is  substantiated; at the same time, it is indispensable to take into account  some  properties of a specific soil, such as  particle size distribution and  cation exchange capacity. The diagnostics of soil potassium status in the long-term field experiments conducted in the forest-steppe zone of West Siberia was carried out.

Results and conclusions. It was found that over 40 years of the experiment on the meadow chernozemic soil (Gleyic Chernozem) with initially very high potassium supply the content of exchangeable potassium decreased from 60 to 30 mg/100 g soil; at the same time, the level of easily exchangeable potassium decreased from 4.0 to 1.1-1.2 mg/100 g soil, indicating a significant deterioration in soil desorption capacity in relation to potassium. In the gray forest soil (Phaeozem) that was initially supplied with potassium, the content of its exchangeable and easily exchangeable forms decreased in 5–7 years of experiments to a critical minimum level, i.e. from 12 and 2 to 6–7 and 0.4–0, 5 mg/100 g soil, respectively. During the subsequent years (25 years) this content remained unchanged. It is concluded that systematic application of potassium together combined with nitrogen and phosphorus background fertilization ensured optimization of potassium status of soils.