POTASSIUM IN DRAINED PEAT SOILS OF NORTHERN TRANS-URAL REGION

Abstract

Results are given from long-term investigations on determining the potassium content in drained peat soils and on evaluating the influence of soil-conservation techniques on its dynamics. The objects of investigations were medium-peat soils, genesis of which was typical of subtaiga (the bog Ernyakul located on the watershed of the Tobol and Vagay Rivers; the bog Usalskoye located on the second terrace above the floodplain of the Tobol) and of forest steppe (the bog Tarmanskoye; the object Reshetnikovo located on the second terrace above the floodplain of the Tura River) in Northern Trans-Ural Region. It has been found that the total potassium content in bogs located on terraces is 3.7-4.6 times more than that in watershed bogs. The long-term (13-15 years) application of potassium at the rate of 90-120 kg a.i. per ha provides conservation of its total reserves. In peat soils with normal ash content, mobile potassium makes up 74.1-96.6 percent of the total potassium content. Major mobile potassium is in the 0.4 m soil layer. The single application of high potassium rates (150 kg a.i. per ha and more), especially the application of potassium as a reserve for a number of years, cannot be allowed. At the 0.5 m level of underground water, about one third of potassium applied moves outside the limits of the root layer. The application of 300 tons of clay per ha increases reserves of mobile potassium by 282.4 kg, sand by 103.4 kg, humus horizon of meadow-swamp soil by 230 kg per ha. The high rates (600-900 t/ha) of clay considerably increase the fixing ability of peat soil. It is inexpedient to strive for creating a high level of potassium availability on peat soils. This results in heavy unproductive losses of potassium and poorer quality of products. The essential condition to increase the effectiveness of potash fertilizers is a split application that provides deficit-free potassium balance in soil.