H. Dou et D. Steffens, MOBILITY AND AVAILABILITY OF PHOSPHORUS F ROM ORGANIC AND INORGANIC FORMS IN THE RHIZOSPHERE OF LOLIUM-PERENNE, Zeitschrift fur Pflanzenernahrung und Bodenkunde, 156(4), 1993, pp. 279-285
1.) In Pots (sandwich-technique according to Helal and Sauerbeck), whe
re the soil (A(p)-horizon of an Alfisol-Udalf from loess) was separate
d into a root chamber and an outer chamber (up to 10 mm away from the
root chamber), the phosphorus (P) availability of super-P, rock-P (Hyp
er-P) and organic P [myo-inositol-2-mono-P di(cyclohexylammonium) salt
] was studied. P was applied at a rate of 50 mg P kg-1 soil only in th
e outer chamber. This P fertilization resulted in significant increase
of CAL- and water-extractable P in the treatment with organic P and s
uper-P compared to the P0 treatment. During 6 cuts of Lolium perenne o
rganic P showed the same effect on the P-uptake of plants as super-P.
Compared to the treatment without P, rock-P had no effect on the P-upt
ake. The higher P-uptake of Lolium perenne both in the super-P- and or
ganic P-treatment was reflected at the end of the experiment only by t
he CAL-P content differences between root chamber and outer chamber. T
he highest activity of acid phosphatase, measured in air dried soil wa
s found in the root chamber of the organic P treatment. The content of
EUF extractable organic P was significantly higher in the root chambe
r of the treatments with super-P and organic P than in the P0- and roc
k-P-treatment. 2.) The P elution was studied with 2 soils (A(p)-horizo
n of an Alfisol-Udalf from loess pH: 6.4; A(h)-horizon of a basaltic b
rown soil pH: 5.4) under lab conditions in columns. In the super-P- an
d organic P-treatment leached P was mainly inorganic. In the soil with
low pH value (5.4), P was leached in the treatment with super-P or or
ganic P in a higher amount of organic P than in the soil with pH 6.4.
The results of this experiment do not show in which form the applied o
rganic P was moved to the roots or displaced in the soil.