Depends on what you're growing. It takes awhile.

Dan

It depends how much space you have, how much compost you have, and how must you want to focus on yield. I might start to supplement some day, but for three years I've only used compost (turned in well) and I seem to have good harvests (good enough for my taste...who knows how much more I could be getting).

As a first-time gardener, I'd keep it simple. If something is lacking, you'll find out, then learn for next year. The years fly by and you learn a lot by doing! :)

In a nutshell,

1) if you have clay you need less, if you have sand you need much more

2) if the compost is chicken manure you need a lot less, if it is leaves you need a lot more

3) if you are growing carrots, parsnips or beans you need none (if you composted the year before), if you are growing cabbage you need a lot

There are also natural fertilizers. Wood ash will both provide potassium for your fruiting plants and for carrots, and will lime your brassica, better than any lime or chemfert you may buy.

The real limiting factor is nitrogen, however. There are abundant natural sources in your house, but you may decide to go almost organic, and buy a 50lb bag of urea, to be used as a supplement to compost. It will last you ten years with, say, 1500 sqft of growing area.

The above posters are right, of course. But why guess? Get a soil test.

I built my beds from my native clay, good home-made compost, and stable manures. When I got a soil test after year two, I found I was plenty high in everything except nitrogen, which was extremely low. I have used Blood meal this year with excellent results. Compost does wonders, but in my soil, it's still not enough. You won't know for certain till you test.

We concluded compost wasn't enough for our vegetable gardens...

Used homemade compost alone for years (vermicompost, chicken & rabbit manure + wood shavings bedding & hay, garden waste, leaves, grass clippings, coffee grounds, etc.)

We don't have have full sun all day long, so that limits growth for sure. Yet when we compared our harvest times & sizes with my dad's garden & what is sold at the local farmer's market we realized we needed to do something MORE. This was about 3 years ago.

-swapped out a whole section of the garden & switched to Square Foot Garden planted wooden sides raised beds & amended soil with vermiculite, peat moss, sand + compost
-began adding huge amounts of partially composted horse manure + bedding in off season to increase organic matter content.
-began using the granular complete organic fertilizer (COF) for the heavy feeding crops in the boxes + planting holes of the large vegetables in the other part of the garden (tomatoes, cucumbers, peppers, squashes)

The boxes warm up sooner in spring, drain better all year long (wet winters/dry summers), & are easier to tend the small things like lettuce & carrots.

We were pleased with the results of having earlier harvests & larger vegetables. Some of the cabbage plants that 1st year were a bit too large due to the fertilizer, so I backed off some. I am guessing our homemade compost is excellent for adding organic matter + has some fertilizer benefit, but isn't enough by itself, so have kept using the COF before planting.

I also water the boxes on occasion with compost tea (bucket made, no bubbler), but usually use a hose wand & with mulch don't need to water more than once a week unless we have a heat wave.

I won't go back to compost alone even though our compost is good stuff. In my opinion it's not enough to support growth for the heavy feeders, but is fine for beans, peas, & potatoes.

Our rhubarb has thin stalks despite heavy doses of horse manure + rabbit manure in fall. I am going to give it COF & see if it makes a difference next year.

One thing no one has mentioned so far - at least I don't think they have - is that the nutrients in compost are NOT readily available to plants. Compost requires an active soil micro-herd of worms, fungi, and bacteria to decompose it making the nutrients available. So as Dan said, that takes time.

I have often read that 3 years of adding 3-5" of high quality, diverse ingredient compost gives you a really good bed. Further semi-annual additions keep it in good condition nutrient wise. I have been using homemade manured compost for 20 some years now with excellent results but find that some plants still need supplements now and then.

But the first couple of years will definitely require some form of supplements depending on what you are growing and your type of soil.

You might want to do some reading over on the Soil & Compost forum here for even more info. Plus it has a number of detailed FAQs there on composting pros and cons.

Dave

Glib is right. In my case, I have very sandy, nutrient poor soil. I tried to go 100% organic with compost and organic fertilizers, but found that although we now have lots of worms etc, nutrients were leaching too fast from the soil, and organic fertilizers were not fast enough to keep up. So I use compost with reduced doses of regular fertilizer, and get great growth.

We also have some raised beds, built from compost, native soil (sand), peat moss and pine bark, and it is a totally different story there. This soil mix is nutrient and water retentive enough that I just top dress with compost and rarely need to fertilize at all.

Bagged urea fertilizer is a very strong synthetic fertilizer, not an organic one. There is a difference between it and urea from animal urine.

Compost can vary from very nutrient-poor to nutrient-rich. Here in RainCountry, if we don't cover our compost piles to protect them from the drenching rains, much of the nutrient value is washed out. HOWEVER, even poor compost is better than none at all, as it still will help to retain moisture.

A soil test of your regular soil (with nothing added) will tell you what you're starting with, and you just build on that. Some people have their compost tested, too.

But pay attention to DigDirt, he's leading you in the right direction: plants can't 'eat' compost or soil nutrients directly, the soil microbes have to break down both into a form that the plants can take up.

The big myth of soil fertilization for the past 70 years has been to 'feed the plants directly'. It doesn't really work -- you have to feed the soil (and microbes, bacteria and fungus), and the soil acidity and those creatures will feed the plants after they break down the components so the plants can absorb them. Without that breakdown, the plants are surrounded by good food, but they've got duct tape over their mouths so they can't eat it. So to speak.

A good complete organic fertilizer probably won't hurt anything, as long as you don't overdo it.

Sue

And finally, there is a difference between hot composting, where the compost is intentionally sterilized, and cold composting, all the better if tree roots get into the pile and inject it with mychorrizae, which comes largely with a complete micro-flora package. And there is a difference if the garden was previously woods or a bush area, or lawn, or new subdivision.

The soil test could tell you for sure but I can tell you that being in WI means you are starting out with pretty rich soil. In my garden I do think that compost is enough. And I get great results.

Thanks for the replies everyone. My soil is definately not loose and sandy, and tends to be more on the clay side, although not the really hard stuff. My situation is basically that the hard nasty clay is about 18" down, leaving me with lots of topsoil to garden in. I plan to try & grow sweet corn next year, which I know is a nitrogen hog, so I'd have to imagine I'm going to need to supplement it. Right now I have the dead sod that I solarized sitting in my compost bin, which I plan to add back to the garden next spring. I also intend to add my yard waste down the road, because I'm sure it won't be ready by spring if I pile it up this fall. I just added composted cow manure, so a soil test right now would probably not give me accurate results. I suppose that at a minimum, adding compost will improve my drainage over time, which is a good thing. Thanks again everyone!

Joe

If you have 18" of topsoil on top of clay, you should be able to retain your nutrients very well. I suspect you won't need much more then the compost. Your most likely issue will be drainage, and compost will help with that. Good luck!

to follow up on compost for the garden results:
I might change my answer that compost is enough because we had different results last year when we moved the garden & built new raised beds in a recently cleared area. Our 1st garden in the new location with a lot more sunlight had amazing growth as compared to a few hundred feet away. We joked that with sunlight you can grow anything & there must be some truth to that though some of the stunted growth in the old garden was from the tall conifer roots soaking up the moisture & nutrients.

I moved our rhubarb one day in late March to the new spot outside of the raised beds & observed incredible growth all season. Granted the plants were larger last year than 5 years ago when first planted, but still it was an amazing difference from 2013 to last year 2014 in the new spot. You'd think the plants would have been stunted by digging them up, but because my soil was so loose from the compost amendments it was easy to keep the clumps intact & cart them over to the new spot with the clump of soil attached then I just mulched around after planting. Where before I would wonder what was wrong with my rhubarb that wasn't huge yet like my dad's now I know it was lacking sunlight not nutrients.

Mulch & occasional watering was all we did for the rhubarb back in the old garden & the new spot. I won't spread my compost on it because applying manure when dormant in fall and early winter is easily composted by spring with the rain washing the nutrients down into the soil. I save the compost for mulching in early summer when the soil has warmed.

You may use 10 to 1 diluted urine for fertilizer too, it works pretty good for me, no more chemical fertilizer.

This post was edited by JCTsai on Sat, Jan 10, 15 at 15:39

use Kitchen scraps, urine, coffee ground, liquid grass clipping may be good enough for your vegetables