Shifting cultivation done in patches in Indonesia was suggested a better model as opposed to executing the practice along forest edges as done in Peru. The system is primitive and only sustainable under low population density and abundance of land. Shifting cultivation in Peru led to site nutrient depletion and build up of Aluminum toxicity. Low nutrients at end of fallow period suggests 10 years is inadequate for sites to rejuvenate to original status. The agroforestry model for sustainable agricultural productivity was shown for Kenya where maize was intercropped between Leucaena alleys.
Improved growth is enhanced because of a synergistic interaction between trees and crops.
Apart from utilizing different resource zones in such systems, trees pump nutrients from deep soil, making them available for shallow rooted crops. Next was the presentation of a Eucalyptus model grown in six year rotations for pole production in Australia. Such short rotation crops have significant impact on soil nutrient reserves. Timmer compared nutrient exports from three harvests of a 7 year old rotation with one harvest of a 21 year old rotation of Eucalyptus plantations in Australia. Mg kgha -1 when harvested three times at 7 years compared with one harvest at 21years.