Full explanation
Regional top-dressing windows across Ukraine: South (Odesa, Mykolaiv, Kherson) — Feb 15 – Mar 5; Forest-Steppe (Kyiv, Poltava, Vinnytsia) — Feb 25 – Mar 15; Polissia (Volyn, Rivne) — Mar 5–25. Field readiness criteria: (1) soil thawed 5–10 cm deep; (2) tractor leaves no tracks deeper than 3–4 cm; (3) mean daily temperature turns positive. Fertilizers: AN (nitrate form immediately available in cold soil) preferred for 1st top-dressing 100–150 kg/ha (34–52 kg N/ha); UAN-32 for 2nd at BBCH 30–32; urea with NBPT for 3rd (if needed) at BBCH 37–39. Risks: (1) missing the window — N reaches tillering instead of peak-impact stage; (2) application on unfrozen tilled surface — rain-leaching losses; (3) application on snow cover — uneven distribution. Recommendation: monitor weather forecast, avoid applications before 14+ dry days.