Asssessment of soil potassium status in Central Chernozem Region under different intensity of potassium fertilizers treatment
Studies carried out on a farm scale experiments with sugar beet showed that when sugar beet was grown on a dark grey forest soil with increased levels (according to Chirikov method) and high levels (according to Maslova method) availability of potassium, a significant increase in the yield of roots relative to the background (NP) was observed in all the treatments with application of potassium fertilizers. When growing sugar beet in a similar experiment on the leached Chernozem with a initially high content of available potassium, statistically significant increase in the yield of root crops relative to the background NP was obtained at a dose of 140 kg K<sub>2</sub>O/ha. Potassium fertilizers increased the yield of root crops and their sugar content. When comparing the results of potassium determination obtained by the methods of Maslova and Chirikov, differences were found that can affect the assessment of the fertility of a particular soil with respect to potassium, which indicate different mechanisms of the extractants impact on the soil absorbing complex. For instance, in depleting conditions in the background NP treatment on the dark-grey forest soil, the exchangeable potassium content decreased by 21 mg /kg of soil, or 23%, relative to the initial content which led to a change in the potassium availability by one level, while according to the Chirikov method, the preservation of the initial security was observed. In the leached Chernozem in the variant with NP fertilizers application both methods reflected the original availability levels of exchangeable and mobile potassium. For a more objective understanding of the soil potassium status, the combination of different methods is preferable, which can identify the expediency of application of potassium fertilizers and their agronomically effective doses.