Leafy Vegetable Fertilization Guide

Colour depends on the balance of nitrogen, potassium and magnesium rather than nitrogen alone. Magnesium is a component of chlorophyll — without it, extra nitrogen cannot produce full colour. Lower leaves yellowing while veins stay green typically indicates magnesium deficiency.

Usually insufficient potassium during heading, or continued high nitrogen that pushes outer leaf growth instead of head filling. Switch to a high-potassium formula early in heading and maintain magnesium for outer-leaf photosynthesis.

The cycle is short, so typically a basal application before transplanting plus one to three topdressings, adjusted to crop type and days to harvest. What matters is not the count but whether the nutrient profile is right at each point — nitrogen-led early to drive growth, shifting to high potassium mid-to-late for head formation and quality.

Softening and water loss after harvest tie directly to insufficient potassium. Potassium raises cell turgor and tissue density, so a high-potassium formula applied as a mid-to-late topdressing produces firmer leaf tissue that holds up better after harvest, reducing transport losses and rejections.