Mesresha, please be very careful on how much you rely on " natural fertilizers" as opposed to chemical fertilizer and taxing their use to make certain there is enough to accommodate all agricultural needs, and the labor energy in using them is fully recovered by the increase in yield. I don't think this is possible, as we have already greatly exceeded the earth's natural carrying capacity. Please review the following webpages:  

https://smallholderagriculture.agsci.colostate.edu/sustainability-of-sm…

https://smallholderagriculture.agsci.colostate.edu/organic-source-of-nu…;