Healthy soil has the ability to cycle nitrogen to plants from the activity of microbes with no outside supplementation. Healthy soil requires the presence of live plant roots throughout the year, e.g. cover crops, with no more than three weeks dead space. If one added compost at a high rate every year, the soil could become nutrient sufficient after many decades. In the meantime, a grower needs to fertilize in addition to using compost.
The missing piece from this discussion is biochar. Biochar raises the cation exchange capacity (CEC) of soil better and more permanently than compost, meaning more nutrients will be available to plants for a longer period. If small portions of biochar are added annually to a plot of land, poor soil health can improve to a self-sustaining level in only a decade or two because it harbors a plethora of soil biota. Once soil reaches that state, it becomes a treasured renewable resource rather than a recurring receptacle. Biochar that is pre-charged with nutrients and inoculated with microbes can bring soil to a regenerative state most quickly.
|Photo by Willi Heidelbach (CC BY 2.0)|
You can be a successful grower by relying on synthetic fertilizers, or you can be even more successful by following organic practices, including natural fertilizers and compost, but unless you grow on prime farmland already, you can only be fully successful in your lifetime if you use biochar. Until your soil gets to that point, keep the fertilizer handy (but please hot compost the manure).