Ghina, it is very difficult to speculate about the reduction in available K, especially with RP, NH4NO3 , Pseudomonas , AMF etc. Dr Hani is very pertinent in his response. Possibly , it could be plenty of Ca released in soil solution , hampering the availability of K . And Ca2+ being divalent cation , could impose some restriction on the mobility of K+ ions+ . In fact , in a system where  three cations ( K, Ca , Mg ) are involved , there is a tripartite relation between them ( Ca plus Mg  restricts the mobility of K  , and often under such system , K-availability is dictated  by the ratio of  K divided by Ca plus Mg) . You need to see the role of Mg as well to arrive at some concrete answers.

P solubilisation  is depend on the pH of soil. so before planting you should check the soil pH if pH of soil indicate alkaline means the availability of p is less apart from that  in acidic medium the availability of p is increases. Several researcher has indicated the solubility rate of P is approx  1 % of total weight. so pH and zero point charge is most important for solubility of P.  i have attached  send one of the best book related this topic which can help you....