Update app.py

app.py

@@ -781,7 +781,7 @@ class NutrientCalculator:
         s_needed = self.target["S"] - self.actual["S"]
         
         if k_needed > 0 and s_needed > 0:
-            k_from_k2so4 = min(k_needed, s_needed * 0.44874 / 0.18401)
+            k_from_k2so4 = min(k_needed, s_needed * k_fraction / s_fraction)
             self._apply_fertilizer("Калий сернокислый", "K", k_from_k2so4)
         
         remaining_k = self.target["K"] - self.actual["K"]