The profitability of short-rotation forestry balances growth against costs of establishment and maintenance. These basic principles apply:

• In general terms, faster tree growth yields a healthier plantation.

• Shorter rotations are harvested sooner to recoup establishment and maintenance costs.

• The grower invests in management at a cost to improve income at harvest.

There are several options to consider, from establishment to harvest (Table 6). One option is the choice of using productive lands or marginal lands. Productivity varies among species and clones of the same species, and matching species or clones/varieties with site conditions is crucial for best stand productivity and health. Planting densities determine the girth of the tree over time. High-density forests will maximize total wood biomass per unit area by producing trees with smaller diameters while less dense forests will produce larger diameter trees but fewer trees overall. Less-dense stands require more weed-control maintenance than more-dense stands. Weed control matters most during the first few years. Chemical weed control support better growth in the first three years. Once a forest closes canopy, mowing and chemical control yield similar growth.

To fertilize or not to fertilize? Like all organisms, trees need adequate nutrition for good growth and health. Trees planted on poor or marginal soils will respond to fertilization but so will competing vegetation or weeds. Use of fertilizers can also have negative off-site impacts. We have compared poplar productivity in trials of fertilized and unfertilized soils with the same intensive weed control management. Weed control without fertilization yielded equivalent or better growth than fertilization with limited weed control.

We found no significant difference in productivity between unfertilized short-rotation forestry stands and those treated with one fertilizer application in the first year of establishment (Figure 23). We recommend focusing on weed and grass control only for maximum stand productivity at minimal costs.