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How to fertilize onions at planting time??

Posted by bart1 6/7 Northern VA (My Page) on
Thu, Apr 3, 08 at 10:24

I received my order of onion plants from Dixiondale yesterday and this is my first attempt at planting them and I'm a little confused.

In the planting guide that was supplied they say to "make a trench in the center of the bed 4" deep and distribute the fertilizer in the trench. Then cover the fertilizer with 2" of soil and plant the transplants 6" from the trench. Do not plant the transplants in the trench!"

I called Dixondale to ask about this because I inteneded to plant one long row of onions instead of 2 rows on either side of the trench. The woman I spoke to said that she's been telling people to put the fertilizer in the trench, partially fill it with soil and then plant the onion plants in the trench. She said she's been giving this adivice for 10 years with no complaints but she also said that the growing guide was reworked for this year.

So my question is, where do I put the fertilizer, below the plants or next to the plants? Also, is there anything wrong with planting one long row as opposed to many shorter rows?

Thanks!
Bart


Follow-Up Postings:

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RE: How to fertilize onions at planting time??

Hi Bart,

The general rule is that the fertilizer should not come in contact with the plant or roots so as to not burn the plant. This, however, depends on the type, quantity and strength of the fertilizer. Light applications of organic or slow release fertilizers are less likely to burn than say a strong, fast release lawn fertilizer.

In your case with a single row of onions, I would sprinkle the fertilizer on both sides of the row and rake it into the top inch or two. No problem with a single row - I often plant a single row around my garden border.

TomNJ


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RE: How to fertilize onions at planting time??

  • Posted by bart1 6/7 Northern VA (My Page) on
    Thu, Apr 3, 08 at 13:43

Thanks Tom!

I re-read the instructions and picked up some fertilizer at lunch and now I have a few more questions.

Dixondale recommends planting the plants in a 4" high raised bed with 2 rows of plants per bed with the 2 rows spaced 12" apart down the bed and the trench of fertilizer between the 2 rows. Within the rows the plants should be spaced 4" apart. So I think I'm going to go with one long raised bed with 2 rows of onions in the bed.

They also said to use 10-20-10 fertilizer, but all I could find was some organic 5-10-5.

Now here are the questions:

1) Why are the plants spaced 4" apart in rows, but the rows are spaced 12" apart? Can I move the rows closer together, say 6 or 8" apart? I was going to run a soaker hose between the rows of plants and I'm worried that 12" apart may be too far for them to get properly watered.

2) Should I bother to use the trench method for the fertilizer (fertilizer below the plants), or sprinkle it on top? Or both?

3) Since I could only find 5-10-5 instead of 10-20-10 should I double the application amount?

Thanks again!
Bart


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RE: How to fertilize onions at planting time??

Hi Bart,

Most people recommend raised beds for onions and garlic, mainly to provide a soft soil texture for bulb formation, but I have never done so. I loosen the ground thoroughly, plant the onion plants, and pack hay between the rows when they are about a foot tall. There are many methods that work.

The row spacing is intended to give enough room for each plant to grow without crowding, which could cause smaller bulbs. I plant mine with one foot between the rows and six inches spacing within the row to allow large onions (I'm growing Walla Walla and Candy which tend to be large). Four inches between onions in a row is quite acceptable for average size varieties. If you would like to space the rows eight inches apart, just stagger the onions in the two rows to maximize spacing between plants. Since your onions will be competing for nutrients and water, be sure to give them plenty of both.

If you can reasonable work the fertilizer into the top inch or two of the soil, that would be best, especially for organic fertilizer which needs to break down in the soil to release its nutrients. With inorganic fertilizer this is not essential as the nutrients will dissolve in water and work their way down to the roots in time. I just sprinkle my inorganic on top of the soil between rows.

5-10-5 fertilizer is the same ratio as 10-20-10, so just use twice as much. Onions like a lot of nitrogen (first number), so you may want to add a little lawn fertilizer such as 29-3-4 or similar to give the nitrogen a boost. Just be sure it is plain lawn fertilizer and not the kind that kills weeds or bugs, or prevents crab grass. Alternatively you could use a 10-10-10 garden fertilizer.

TomNJ


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RE: How to fertilize onions at planting time??

  • Posted by bart1 6/7 Northern VA (My Page) on
    Fri, Apr 4, 08 at 7:43

Thanks Tom!

Every time you answer one question, it makes me think of two more!

Regarding the use of weed killer fertilizer (or not), the growing guide recommends to "apply a pre emergent weed control such as Treflan or Corn Gluten into the top 1" of soil and rake in to incorporate". Is this opposite advice of what you recommend?

I'm starting with onion plants, not seeds so I figured a pre emergent weed killer would be ok. The only thing my local garden store had (that fit the bill of "corn gluten") was Organic Preen which the salesman told me was corn gluten although I didn't see that name mentioned on the packaging.

Anyhow, my question is should I use the pre emergent weed killer at planting time to get them off to a good, weedless start?

Thanks again, your advice has been fantastic,
Bart


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RE: How to fertilize onions at planting time??

Hi Bart,

I suppose an organic pre-emergent would be okay. I personally avoid any weed killers, herbicides, or pesticides of any kind in my veggie garden, but I do understand some are indeed harmless. I use a heavy hay mulch which prevents weeds very well. It also holds soil moisture, stabilizes soil temperature, reflects light up to the plants, and slowly breaks down to provide nutrients. Spoiled feed hay works best as opposed to straw or salt hay, but there are many good mulches available.

BTW, I forgot to mention than another major benefit of a raised bed is improved drainage. My soil drains well so I don't bother.

I planted 238 onion plants (from Dixondale) on Wednesday and will hand weed for a few weeks while the soil warms up, and then apply the hay in early May.

TomNJ


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RE: How to fertilize onions at planting time??

  • Posted by bart1 6/7 Northern VA (My Page) on
    Fri, Apr 4, 08 at 9:38

Thanks Tom!

I also have really great drainage so I'll probably avoid the hassle of doing a raised bed. I'll also mulch heavily with straw or shreaded leaves.

Thanks again,
Bart


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RE: How to fertilize onions at planting time??

look, onions or garlic (same family) do not like a lot of fertilizer but do like rich soil amended with compost. a sandy loam is very good. afaik onions do not like a lot of N, nitrogen promotes green growth. onions do like a lot of P, phosphorus promotes good root growth. i do not put any fertilizer on newly transplanted plants, none. these plants need to adjust to the new location and i think feeding them right away is not a good thing. also i only fertilize my onions 3 times in the season a month apart. garlic i never fertilize. oh btw, doubling 5-10-5 is a bad idea imo. too much fertilizer is not good for onions, if you want 10-20-10 then use that. i use neptune's harvest fish emulsion or seaweed and fish emulstion and these are around 2-3-1 iirc.

depending upon the variety and therefore the finished bulb, 4" on center is the closest to plant and 6" on center is better. i found that if you crowd them the bulbs will be smaller than if you give them adequate spacing. ailsa craig exhibition or candy at 4" on center don't size well, 6" on center is better but 8" on center is best. ace and candy are huge onions. i used to plant copra 3" on center but they were too small and 4" on center yields a bigger bulb, this year i'm trying 6" on center for copra. so you need to know the final size of your onion, the huge bulbers need all the room you can give them to maximum their size.

pre-emergent? why use that? hopefully you know that onions do not tolerate weeds so you need to keep them well weeded. it's a hassle but necessary. so skip that pre-emer stuff.

i plant my onions in 4' X 4' blocks with 3 blocks in 1 4' X 12' block. you can weed from either side and it saves space.

tom


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RE: How to fertilize onions at planting time??

Hi Tom,

My recommendation for a high nitrogen fertilizer for onions is based on multiple websites that relate the bulb size to the health of the top growth. In particular, I respect Dixondale Farms who state on their website:

"The size of the onion bulb is dependent upon the number and size of the green leaves or tops at the time of bulbing. For each leaf, there will be a ring of onion. The larger the leaf, the larger the ring will be when the carbohydrates from the leaves are transferred to the rings of the bulb.

Once the onions are established (three weeks after planting), they'll require more nitrogen for leaf formation. An onion typically generates a new leaf every 2-3 weeks. When you receive your transplants from us, they generally have 4-5 leaves. The perfect onion has 13 rings, so the key is to generate as many large leaves as you can before the onion starts bulbing.

Feeding the onion every 2-3 weeks with a good source of nitrogen, such as ammonium sulfate (21-0-0), is essential. Water the onions after every application, because the only way for the plant to take up the nitrogen is through the root system. Once the onion starts bulbing, additional nitrogen shouldn't be applied, since it will produce bulbs with thick necks. These won't shrink on drying, and therefore won't store well."

Another source, the Utah State University (http://extension.usu.edu/files/factsheets/onionsf.PDF) say:

"In addition to the fertilizer used at planting, onions need additional nitrogen fertilizer to produce optimum yields. Sidedress onions with lb of nitrogen fertilizer (21-0-0) per 100 square feet in late May and June. Do not fertilize after mid-July as extra nutrients stimulate late season growth and reduce storage potential of dry onions."

There are many other sites that take the same position. Naturally adequate Phosphorus and Potassium are essential for most plants, especially root crops, but a strong top growth seems to be even more vital for onions. I just learned this this year after decades of growing onions and am giving it a try this season.

TomNJ


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RE: How to fertilize onions at planting time??

tomnj,

do i know you???? i know a tom from nj on gardening sites. he had a wonderful yellow tomato. well tom i agree that the number of green leaves will equal the rings in the bulb.

i was going to ask how many seasons you have grown onions but you've been doing it at least twice as long as i have.

i've read that onions don't need much fertilizer but do like rich sandy loam. as an organic gardener, i'd be more likely to add compost at planting time and leaves/manure in the fall to build healthy soil. as stated i only fertilize 3 times in the season and it's weak fertilizer. my results are quite acceptable. from 3 4' x 4' plots i harvest from 33 to 40 pounds of onions (candy, copra and red wing) per 4' x 4' plot. my candy and ace (ailsa craig exhibition) were 6" in diameter and they can get bigger but i plant at 6" on center, last season i planted candy not ace at 6". i stopped growing ace so i can't say if 8" would help but in my experience the more room the bigger the bulb.

i'd be curious if additional fertilizing this season gives you better results. however, faster growth and a larger bulb may result in decreased storage (just wondering this) and if so then that's not good. i grow for storage that's why i grow these 3 varieties. i just started eating my copra last week.

keep in mind, as you probably know, a lot of people over fertilize their tomato plants and get huge plants with lush jungle vegetation but marble sized tomatoes. they grew huge plants with too much N and as a result the fruits suffered. this is why i maintain based upon what i have read and my results that you don't need to fertilize onions all that much. my soil is different than yours so's my climate. i suppose there's more than 1 way to skin a cat or grow an onion.

tom


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RE: How to fertilize onions at planting time??

Hi Tom,

It must be another Tom from NJ that you know - I grow lots of red tomatoes but no yellow ones :-)

I grew organically for many years, but now I am "semi-organic". I use compost and never use any insecticides or herbicides, but I do supplement with some inorganic fertilizer because my compost no longer contains manure (just grass clippings and leaves).

I use nitrogen sparingly for the very reasons you stated and always assumed all root crops preferred lots of P & K. So I was surprised to read last year that onions and garlic need lots of N during the early stages to promote vigorous top growth, and even read somewhere that P & K feedings were ineffective. My last soil test in November showed excessive levels of P & K, so this year I am just adding a bit of high N fertilizer to compensate for my lower grade compost. I'll stop the N feedings before bulbing begins. Right now I have 232 garlics (9 varieties) and 238 onions (Walla Walla, Candy, Red Zeppelin) in the ground and it will be interesting to see how they come out with this change in feeding.

TomNJ


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RE: How to fertilize onions at planting time??

I plant my onions in a wide row 10 inches on center and I don't fertilize untill they are 6 or 8 inches high. I use 12-12-12 about 3 times a year and hand spreed it around them and then I cultivate it in. I also give them a shot of epsom salts at the same time. I have tried puting fertilizer below the plant and it burnt the plants and killed them. [I mite not have got the fertilizer deep enough] but I won't try it again.You guys are making me feel bad planting allready we got 6 inches of snow yesterday and we are still making maple syrup.
YOPPER P.S.Tom from C.T. its good to see your out and about


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RE: How to fertilize onions at planting time??

hi yopper, 6" of snow!! that "up" sure is cold.

tom, i don't see why your compost is inferior with out manure. i only add greens and browns to my pile but never manure as i just don't have it. once every 3 or 4 years i have some fresh manure dumped in the garden in the fall when i till it in with leaves. too much manure accumulates salts. i learned this after i put 14 yards of manure 1 year and 6 yards a couple of years later into my 1200 sq ft garden. i thought more was better but not always.

tom


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RE: How to fertilize onions at planting time??

Hi Tom,

My compost is about equal parts grass clippings and leaves, and the nitrogen content of the grass clippings is not enough to fully breakdown the leaves. Manure in the compost would add the nitrogen and bacteria needed to complete the job, but since I don't have access to manure at this time I add some inorganic fertilizer with high N to help. I could add dried blood as I used to, but at $6/5 lb bag I just sprinkle some lawn fertilizer while building the heap.

I refer to my compost as lower grade because I build it in layers and it does not fully breakdown by the time I need it the following year. It still adds valuable organic matter to the soil, but it could take N from the soil to complete the breakdown. I have had N deficiencies before after heavy compost additions. Now that I have taken early retirement :-) I have more time and will attempt to build the heap faster and turn it more often. And maybe this year I'll switch back to dried blood and bone meal as additives. That will bring me back to full organic gardening next year.

TomNJ


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