You might check out "biochar".

People are going to tell you to get a soil test from your local ag extension. You're flying blind without knowing what is in the soil, but if it's just a tiny garden (like mine) it may not worth the cost of a soil test.

I think the general suggestion is an organic fertilizer that is around 1:2:1 NPK ratio used according to guidlines on the package. If the fertilizer you find has less phosphorus than that, add some bone meal or rock phosphate (just enough to adjust to ratio of P for overall fertilizer to what I just mentioned). Also, if you live in an area with fairly high rainfall, some lime once or twice a year would be probably good. Its common to hear warnings about over-liming, but from what I've read it becomes harder to raise PH more once it reaches around 7.0. I think most vegetables like Ph between 6 and 7, so go easy on it, but it's pretty hard to ruin the soil AFAIK.

Dolomitic lime can also add magnesium, but supposedly using it exclusively can add too much, which causes problems, so rotating this with other kinds of agricultural lime might be a good idea.

Compost, compost and more compost (including the chicken poo IF it is well aged first).

But pro soil test - yes - if only to find out what the pH of your native soil is if nothing else. Lots of compost will eventually bring it into line if it is way out of kilter and will only keep it there with regular 2-3x a year compost additions. But you need to know which pH you are working with in the native soil. EX: I have very alkaline native soil 8+ so while I can safely use lots of acidic leaf-based compost and some manures I cannot use any lime or wood ash or too much manure.

So for best results get a professional soil test and go from there.

Dave

It never hurts to add plant matter compost to improve the organic content and texture of the soil. I, myself, buy large bags of dehydrated composted cow manure at the garden center and til it into the soil before planting tomatoes. Generally I don't need to add other fertilizer once tomatoes are planted.

1.) Soil test.
2.) Add as much compost as you can reasonably get your hands on.
3.) As Mulio said, biochar is an awesome addition to soil and will pay dividends in the years to come.

Organic gardening is a whole different mindset. Instead of watering-in soluable nutrients, you need to mix-in (or top-dress for no-till - which is what I do) your organic amendments, be they fertilizers or otherwise.

Adding the compost and biochar will help increase your soils ability to retain the nutrients you put into it and it will increase your plants ability to get the nutrients out of it.

It is important to note that finished compost and biochar are not fertilizers, but rather they are soil amendments. Aged chicken manure, depending on how old (or "hot") it is, is a great fertilizer and could be mixed in with the biochar and and finished compost and would give your garden a great headstart. If you're prepping an organic garden to plant into immediately, I would mix in my fertilizer at the same time - in your case, the chicken poo.

If you go the route of having a soil test done, which is highly recommended, you may want to add other soils amendments, but I wouldn't try doing those (lime, etc.) without seeing the results.

Another vote here for a soil test. Be aware, however, there are several difference types of soil test and many ways of interpreting their results, depending on the lab, test solutions, etc. The main test types are base saturation, nutrient maintenance and sufficiency level. Base saturation is predicated on the assumption that their is an "ideal" nutrient balance to promote healthy soil biota and, hence, healthy plant growth. Nutrient maintenance is based on applying what is need to grow the "next crop" regardless of what's currently available in one's soil. Sufficiency level is based on anticipated yield levels. For example, based on what's currently available in the soil, what is the likelihood that additional potassium (or calcium, magnesium, etc.) will provide a yield response.

As a sustainable gardener (I don't strive to be 100% government-approved organic), I like the base saturation test. In my mind, it's geared towards creating the ideal growing environment-rather than focusing simply on fertilizing the plant. You can think of this as "feed the soil" vs. "feed the plant."

Regardless of your approach, be careful of "chasing pH." The relative alkalinity (or acidity) or your soil is influenced by several factors. For example, a high pH might be due to too much calcium, magnesium, potassium or sodium. Conversely, low pH might indicate insufficient levels of any of these. Without a soil test, it's hard to know.