39
(Table 5-1). Maximum yield of inoculated plants was achieved between 28
and 30 mg kg of applied P. Control plants had a linear relationship
for shoot dry weights and a quadratic relationship for root fresh
weights. There were fungus x P interactions for shoot dry and root fresh
weights (Table 5-2).
Percentage and total root length colonized by VAM fungi for the
inoculated treatments increased with P additions (Fig. 5-1). This effect
was greater for G. etunicatum than for G. intraradices. Phosphate
application did not alter the percentage and total root length colonized
in the control plants. Inoculated plants had a quadratic relationship
for percentage and total root length colonized and applied P
(Table 5-1). Maximum colonization of inoculated treatments, expressed
as either percentage or total length of colonized root, was attained
between 32 and 35 mg kg-^ of applied P. There were fungus x P
interactions for percentage and total root length colonized by VAM fungi
(Table 5-2).
Shoot dry weight of Siratro over the range of applied P was highly
correlated with percentage (r2 = 0.95") and total root length colonized
O V*. J,
by VAM fungi (rz = 0.97"') (Fig. 5-2) for both inoculated treatments.
Percentage of the root colonized by VAM fungi was very closely correlated
(r2 = 0.98*>') with the total root length colonized.
Growth enhancement from VAM inoculation at different levels of P has
been reported to vary with VAM fungi (Hayman and Hampson, 1979; Hayman
and Mosse, 1979; Schubert and Hayman, 1986; Thompson et al., 1986). For
example, Schubert and Hayman (1986) indicated that, when large amounts
of P were added (more than 100 mg kg *), G. mosseae, G. versiforme, G.