Major nutrient removal figures show that nitrogen and potassium are the nutrients needed in relative greatest quantities in onion and garlic crops. They are fundamental for achieving high marketable yields.
High rates of nitrogen are needed to satisfy crop demand. However it is important not to over-apply nitrogen, particularly in bulb onions, as this can delay maturity, soften bulbs and lead to storage rots.
While much lower levels of micronutrients are needed to satisfy yield and quality onion crop production, the correct balance of these trace elements is essential.
The key micronutrients needed in greatest quantities are boron, and iron. These have an influence on yield and quality. Zinc also pays a role in seed germination.