Just for info, hardwoods are not necessarily the most productive producers of biomass, and this could vary with species, as some grow faster than others. On some soils with nutrient deficiencies, fertilization can be justified as to cost and benefit. However, the best soil scientists will tell you to test the soils first before you waste money on fertilizer, or the wrong fertilizer, or application rate, timing, whether it should be pelletized or not, etc. I have a couple papers on fertilizing loblolly pine, that I might be able to send if you want, but there still should be some on the internet.