RESPONSE OF SOYBEAN (Glycine max L.) TO BIO AND MINERAL PHOSPHATE FERTILIZATION UNDER DIFFERENT LEVELS OF SOIL MOISTURE.

Two field experiments were conducted at Gemmiza Agricultural Research
Station, Agricultural Research Center Gharbia Governorate, Egypt, during 2000 and
2001 seasons. The aim of this investigation is to study the difference between
superphosphate application and inoculation with phosphate solubilizing
microorganisms (phosphobactrin and vesicular arabuscular mycorrhiza VAM ) on
soybean variety Giza 21grOWrl under two levels of soil moisture ( 40 % and 80 %
depletion from soil available water).
Increasing available soil moisture content caused significant increases in number
of seeds per plant , seed weight per plant, seed yield ton per feddan , number of
seeds per pod and maturity date in first season , while in second season it caused
significant increases for number of pods, seeds , seed weight per plant and maturity
date. So it caused significant increases for protein and phosphorus percentages. The
inoc!:lla~ion by phosphobactrin , VAM and superphosphate application caused
significant increases for all characters in both seasons except number of seeds per
pod . (Table 3). The inoculation by phosphobactrin solid, micorrhiza solid ,
. phosphobactrin with superphosphate and micorrhiza with superphosphate caused
significantincreases for characters number of branches , pods , seeds , seed weight
per plant and seed yield ton per feddan in both seasons. Inoculation by mycorrhiza
with 22 P2 05 gave the highest values of seed yield ton per feddan (1.830 - 1.850
tonlf~d.) compared to (1.100 - 1.187 ton/fed. of control in the first season, while in
the second season gave (1.730 -1,747 ton/fed.) compared to (1.007 -1.160 ton/fed.)
for control. So inoculation by mycorrhiza and superphosphate caused increases of
protein percentage (41.40 % compared to 37.84 % for control and increases of
phosphor percentage in seeds 0.62 % compared to 0.30 % of control. The available
phosphorus in soil was higher by VAM inoculation than phosphobactrin inoculation
and phosphorus application at rate of 22 P2 051 fed.
Therefore it is recommended to inoculate the soil with VAM and
phosphobactrin and decrease the phosphorus application doses or use rock
phosphate to decrease the costs with soil moisture for field capacity to 40 % depletion
from available soil water.