Trials confirm that a balance between nitrate and ammonium-N is most effective at promoting onion leaf and bulb growth. However, during later stages of growth, nitrate forms provide higher dry matters in the bulb.
Maximizing Onion Bulb Dry Matter Content
The majority of onions and garlic crops are grown for the fresh market. Bulbs should be sufficiently dry for the intended purpose. Most common bulb onions have 10-12% dry matter. Shallots have a very high dry matter content - between 16 and 35% - compared to 7-15% for onions. Onions grown for dehydration require higher dry matters of 17-20%. They are usually made from white-fleshed onions, but chives and leeks can also be processed in such a manner. Nitrogen and potassium are the most important nutrients to influence dry matter content of onion bulbs.
Crop Nutrition and Onion Bulb Dry Matter Content
Nitrate x Ammonium Nitrate
Potassium
Potassium is particularly important where high N rates have been applied (if high yielding systems). In these situations it helps maintain yield by increasing dry matter and sugar accumulation in the bulb.
Recommended Yara Fertilizers for Onions
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YaraMila COMPLEX
12-4.8-14.9 + 8% S - Prilled NPK fertilizer which also contains magnesium and sulphur as well as micronutrients ideal for use on a wide range of arable and horticultural crops.
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YaraLiva NITRABOR
15.5% N + 18% Ca + 0.3% B - Granular calcium nitrate fertilizer with added boron suitable for field application to all crops especially brassicas which are more prone to calcium and boron deficiency.
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MAINCROP S
14-5.7-17.4 + 2.2% S - A quality size matched NPK plus S size matched blended fertilizer, ideal for use for potato production due to the ratio in the of N P and K whilst including a useful amount of sulphur.
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STARTER SOLUTION PLUS
A liquid fertilizer for placement which aids rapid crop establishment, promotes efficient utilization of phosphate and improves phosphate availability.
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YaraVita BORTRAC 150
A liquid micronutrient fertilizer containing 150 g/l boron for foliar application to provide additional boron or to treat boron deficiencies in a wide range of crops.
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YaraVita BRASSITREL PRO
A flowable liquid suspension fertilizer with a combination of micronutrients including manganese, magnesium, boron and molybdenum for foliar application to oilseed rape, brassicas and legumes.