emi eso d fo the greatest potential for very high growth rates in the USA. important as an intensivemanagement tool in recent years (Fox, 2000). Responses to fertilization are generally positive as far as Available online at www.sciencedirect.com Agroforestry systems, as well as many natural tree based ecosystems, are perceived to improve or maintain soil fertility and productivity, to promote soil conservation, reduce soil degradation and achieve sustainable production (Brady and