Hi Ghina,

Faba bean is one of those, since comparatively to other crops, e.g. soybean and maize, releases higher concentrations of organic acids, decreasing soil pH (and consequently improving the availability of some nutrients, such as P). 

You can see Li et al. 2007 at www.pnas.org/content/104/27/11192.full

Best wishes,

may be legumes could be a good source of what you are request. But, look for other types of cops, especially herbs, garlic and onions.