Comparative evaluation of tissue testing methods and fertilizer impacts on onion nutrition, yield, and Stemphylium leaf blight severity in the Holland Marsh, Ontario (2024–2025)

This dataset contains the research data underlying Chapter 3 of Ifesinachi Nelson Ezeh MSc thesis: comparative evaluation of tissue testing methods and fertilizer impacts on onion nutrition, yield, and Stemphylium leaf blight severity in the Holland Marsh region of Ontario (2024–2025). It includes (1) paired onion leaf tissue nutrient measurements collected from commercial grower fields and analyzed using the Picketa Leaf Evaluated Nutrient System (LENS) and accredited laboratory testing (SGS), across multiple fields and sampling rounds; (2) paired onion leaf tissue nutrient measurements from a replicated fertilizer and foliar micronutrient program study conducted at Ontario Crops Research Centre; and (3) SLB Disease Severity Index (DSI) ratings across multiple assessment dates plus onion yield and bulb-size grade outcomes. Nutrients reported include N, P, K, Ca, Mg, S, Zn, Mn, Cu, Fe, and B.