Optimum nitrogen supply is important for onion size. Nitrogen supports production of leaves and hence, increases the number of onion and garlic bulb scales and the size of the harvested bulb. Because these crops are shallow rooted with poor root branching, it is common practice to use split N-applications to maximize uptake efficiency. Placement has been proven to be more effective than broadcasting.
Increasing Onion Bulb Size
Planting density is a very important management factor to determine bulb size in onions and garlic crops. In addition, a good crop nutrition can help growers to achieve a desired diameter. Nitrogen, potassium and phosphorus are essential to influence onion bulb size.
Crop Nutrition and Onion Bulb Size
Nitrogen
Phosphorus
Is important that sufficient phosphorus is available to balance potential losses in store e.g., if too high rates of nitrogen were applied. Phosphorus can be used in such a way to ensure top yields through use of high rates of nitrogen, yet at the same time providing little deterioration in crop quality.
Calcium
Trials with calcium nitrate confirm this is the most effective form of nitrogen for high yields. It is also the most effective formulation in increasing onion bulb size.
Recommended Yara Fertilizers for Onions and Garlic
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YaraVita ZINTRAC 700
A fully formulated flowable liquid micronutrient fertilizer containing 700 g/l zinc for foliar application to prevent and treat zinc deficiency on a wide range of crops.
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YaraLiva TROPICOTE
15.5% N + 18.8% Ca - Granular calcium nitrate fertilizer for field application to a wide range of crops.
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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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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.