We’ve bought a house and land in Bulgaria. The house has been empty and the grounds neglected for 10 years. Before that, it would have had lots of vegetables and fruits grown on it, with application of animal manure from the pig, chickens and goat/sheep who will also have lived here (evidence in the outhouses). My partner reckons the soil is so fertile it won’t need feeding for the foreseeable future. I’m not so sure. We’re not keeping any animals, yet, and I think the ground may be depleted by the 10 years of weeds, so I think we should get hold of some manure to apply over the winter. We’ve grown some vegetables this year, which have been ok. Any advice?
Without laboratory testing of soil samples, the usual test is to plant and see how things grow. You say you grew vegetables this year and they were fine, which would indicate the soil is fertile. A period of being fallow, or lying uncultivated, (assuming the soil is not already a 'dust bowl' which is unlikely throughout most of Europe) does allow the soil to build up fertility and regenerate, and is often done deliberately to allow for this process.
Even so, it's probably not correct to say the soil will not need any organic materials applied for the 'foreseeable future', which might suggest a long period of years; applying composted manure or other organic materials annually to soil is a good idea to keep the fertility up, especially now you've started to cultivate and grow. Which organic materials you use needs consideration though - root crops such as carrots do not appreciate heavily manured soil, but are fine with other organic materials such as spent mushroom compost or leaf mould. The other option is to sow a cover/green manure crop and turn it into the soil; note that it is not usual to plant immediately after turning a crop into the soil, but to wait, so this might be useful for areas you are not intending to plant for a while. Cover and green manure crops, depending on what you use, may also reduce soil born pathogens, which can be helpful when growing annual vegetables. Basic info on this type of crop here http://www.balkep.org/cover-crops.html but there are other sources on the internet which give more complex information for European countries.