Do Onions Need Manure?

Onions are a versatile vegetable and fairly simple to grow if you choose the right variety and take care of the planting dates. Nevertheless, they are heavy feeders and will do well with constant nourishment throughout the growing season. Do onions need manure is this the answer? The onion plants will quickly use up the soil’s nutrients and unless these are supplemented with regular fertilization, you won’t find those big, flavorful bulbs that you expect to dig up at harvest time. 

Do Onions Need Manure

How And When To Fertilize Onions

Before Planting

Before planting the transplants or sets in the garden, the ground will need to be nourished with all the essential nutrients that onions need to grow. If you don’t have access to manure or compost, chemical fertilizers will also do the job. Add ½ cup of a balanced, slow-release granular fertilizer to every 10 feet row and incorporate it into the soil to a depth of 6 inches. 

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If you’re planting onion seeds instead of sets, use super phosphate fertilizer in place of balanced fertilizer but in the same amount. Super phosphate boosts sprouting and encourages the development of strong, healthy roots, setting your plants off on a good start. 

In-Season Care

Onions will need a steady supply of nutrients, especially nitrogen, to produce big bulbs. Sidedress the rows with ½ cup of any nitrogen-based fertilizer in early summers and a second time in midsummers for best results. Don’t apply any fertilizers after midsummer since they will encourage new growth when the onion crop should ideally be approaching harvest. 

See also  How To Fertilize Onion Plants (And When)

Organic Options 

If you want to grow onions organically and avoid chemical fertilizers altogether, amending the ground with a 3-inch layer of composted manure before planting the sets will produce excellent results. Unlike chemical fertilizers, compost also improves the texture of heavy, compacted soil for better development of bulbs. 

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Sidedress the plants with 2 to 3 shovelfuls of composted manure twice during the growing season, incorporating it lightly into the soil, taking care not to damage the bulbs. Make sure you use manure that has been composted for a year at least to lower the nitrogen levels. Though onions need nitrogen, too much nitrogen, such as that present in fresh manure, can burn the plants. 

Avoid Growing On Freshly Manured Soil

As already pointed out, too much nitrogen can damage your onion crop. Never plant onions in freshly manured soil. If you’re using manure to nourish the soil, dig and amend manure into the soil several months before planting onions. This gives ample time for the organic material to break down and adjust soil nutrients to just the right levels that will meet onion’s fertilizer requirements. 


Grow onions in fertile, well-worked, well-drained soil and fertilize adequately with the right sources during the season to produce the best onions.

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