Onions are very easy to care for and don't really need any fertilizer. If you still don't want to do without fertilizing, you should pay attention to the ingredients.
Few plants are really as easy to care for as bulbs. You plant them and wait for the time when you can harvest the bulbs. Especially when it comes to the supply of nutrients, they are absolutely undemanding.
Onions are weak consumers. This means nothing other than that they withdraw very little nutrients from the soil during their growth phase. So you can grow onions well in any soil, even poor soil shouldn't have any problems thriving.
If you still don't want to do without the addition of fertilizer, you should note the following:
❶ Use Organic Fertilizer
In the garden, it is generally better to use organic fertilizers such as compost, humus, etc. In this way, you only use the nutrients that are already present in the nutrient cycle.
In the case of the bulbs, it is sufficient if you work well-rotted compost into the soil in spring or autumn.
❷ Commercial fertilizer
If you have to use a ready-to-use fertilizer from the trade, it should only contain very little nitrogen. Nitrogen is not very good for vegetables. It is also important to ensure that the ready-to-use fertilizer contains mainly potassium and phosphorus. Patent-Kahli from Dehner, for example, is ideal.
» Tip: Carrots have very similar needs, so you can grow onions and carrots together in the garden. Since the onions are so undemanding and undemanding, you can also plant them as a second crop after growing a heavy feeder.