『Abstract
Agronomic studies on soil phosphorus dynamics have primarily
focused on the plant-available inorganic P pool. However organic
P and less labile inorganic pools can contribute significantly
to plant P uptake. The objectives of this study were to determine
the changes in inorganic and organic P pools of varying lability
in and below the plowlayer after 13 years of continuous cultivation
and fertilization on a Typic Paleudult in Yurimaguas, Peru. The
field experiment was established after slash and burn of a secondary
forest and included non-fertilized and fertilized treatments.
The yearly cropping pattern consisted of an upland rice (Oryza
sativa), - corn (Zea mays), - soybean (Glycine max)
rotation. A modified version of the Hedley et al. procedure was
used to sequentially fractionate soil P into increasingly recalcitrant
organic and inorganic pools. Plowlayer accumulation of the fertilizer
P occurred in all P pools. The greatest increase was in the NaOH
extractable inorganic P pool. In the non-fertilized plots, the
organic P decreased by 42%. Phosphorus fertilization resulted
in significant movement of P below plowlayer. The accumulation
occurred mostly in inorganic and organic P pools that are not
quantified by traditional soil-P test methods. In fertilized plots
sub-plowlayer total P increased by 90 μg g-1 (87%)
while resin extractable P increased only 4 μg g-1.
Phosphorus content of the organic P pools below the plowlayer
increased by 24 μg g-1 (50%) in fertilized plots. The
inclusion of less labile P pools in studies of P movement and
the evaluation of P fertilizer residual values could lead to a
better understanding of P dynamics and hence better management
of P fertilization.
Key words: budget; movement; phosphorus』
Introduction
Methodology
Results
Plowlayer
Below the plowlayer
Discussion
Phosphorus budget
Phosphorus movement
Acknowledgements
References
※土壌リンの連続分別法は、Hedley et al.(1982)を修正したものを使用。