LONG-TERM EFFECTS OF POTASSIUM APPLICATION ON YIELD AND SOIL FROM 3 EXPERIMENTAL FIELDS IN SWEDEN

Effects of treatments with no application of K and different amounts o f applied K in three long-term held trials in Sweden with different so il properties were studied. None of the sites had a fixed crop rotatio n but the dominant crop was barley. Average dry matter (DM) yield resp onse, in units of barley, depending on treatment was statistically ana lysed, and the amounts of K uptake and the input and output of K for a ll crops and for ley was calculated. Ultuna, with the highest content of clay, AL extractable K (K-AL) and HCl extractable K (K-HCL) in soil , showed no significant difference in average DM yield response betwee n treatments, while Radde, with the lowest contents of these soil prop erties, showed a significant different average DM yield response betwe en application (40, 80 and 160 kg ha(-1) year(-1)) and no application of K. The average DM yield response at Vojakkala was significant betwe en application (120 and 240 kg ha(-1) year(-1)) and no application of K. The balance between input of K as fertiliser and output of K in har vest differed between sites, where more years with perennial ley in th e crop rotation required larger applications of K to reach a balance. At Ultuna, the needs of K application to maintain yield level was non- existent. Despite poorer soil K properties, Vojakkala and Radde seemed to be able to deliver large amounts of K to perennial ley. At Radde, this ability seemed to increase when K was applied.