On behalf of the Potassium Nitrate Association (PNA), Landlab research station in Quinto Vicentino (Italy), conducted a trial to test the effect on winter wheat yield of two foliar applications with potassium nitrate (KNO3) in spring. The time and placement of foliar application of potassium nitrate caused 17% yield increase even at the highest K level in the base dressing. The foliar application of KNO3 is promoting a higher yield compared to the untreated entries and the foliar applied K is efficient for increase of yield, mainly due to more ears/m2. The yield results are clear and statistically strongly supported at a very high level of confidence. The study is confirming the benefit of potassium nitrate applied twice as foliar spray, in the key moment of the crop cycle, at 10 kg/ha/application over all four levels of K in the base dressing nutrition.