Even when soil tests show “good” or “very good” levels of phosphorus and potassium, many farmers still see yellow fields, poor early growth and white heads — clear deficiency symptoms. Why does this happen? Main causes of P and K lock-up: 1. Wrong soil pH (optimal 6.3–7.2) 2. Cold spring temperatures (<12–13 °C) 3. Soil compaction and poor aeration 4. Ca–Mg–K imbalance (antagonism) 5. Low organic matter (<2 %) 6. Wrong fertilizer forms used in previous years Fast and effective solutions: - liming (calcium carbonate, zeolite) - starter fertilizers (MAP, APP, potassium phosphite) - complex fertilizers with polyphosphates - gypsum application on sodic soils - foliar P + K applications at critical stages - regular plant tissue testing Real-life example (250 ha, Timiș County): Soil test: P 280 ppm, K 320 ppm, pH 5.4 → yield 5.8 t/ha After 3 t/ha calcium carbonate + MAP starter + 2 foliar treatments → pH 6.4 and 8.4 t/ha same year. Conclusion: what matters is not how much P and K you have in the soil, but how much is actually plant-available when the crop needs it most.