DISCUSSION
Fertilizer Effects on Growth
The effect of P fertilization at time of planting lasted beyond the time when
roots had access to readily available fertilizer P (Figure 1). Most likely, little of
the highly soluble triple superphosphate remained by the end of the second year,
and what was not taken up by roots was probably converted to insoluble iron
and aluminum phosphates. Furthermore, although expanding koa root systems
initially had a very good supply of added P, by the end of the second year
they extended well beyond the small volume of fertilized soil. Despite these
factors, increased growth rates were maintained during the second and third
years (Figure 1).