Five willow clones and one hybrid poplar clone were planted during 1987 at
0.3 x 0.3 m spacing and harvested annually for 10 years. Half of the trees
were fertilized annually with N, P and K and all trees were irrigated begin
ning in the third growing season. Annual biomass production fit the logisti
c growth curve well for four of the clones with r(2) values ranging from 0.
91 to 0.54, suggesting that well-adapted willow clones can be consistently
productive for at least 10 years with annual harvesting. Fertilizer did not
increase the maximum biomass production level attained, but it reduced the
time required to reach maximum production by 1 year. The correlation betwe
en annual biomass production and the number of growing degree days during y
ears 4-10 was high, ranging from 0.95 to 0.66. (C) 2001 Elsevier Science Lt
d. All rights reserved.