『Abstract
A reduction on chemical phosphate (P) fertilizer application
to farmland from 137.6 kg P ha-1 in 1985 to 99.0 kg
P ha-1 in 2005 and in manure application from 42.4
kg P ha-1 in 1985 to 32.8 kg P ha-1 in 2005
did not reduce crop P uptake, which averaged 27 kg P ha-1
over the period. Phosphate balance on farmland declined from 153.0
kg P ha-1 in 1985 to 105.4 kg P ha-1 in
2005 while livestock excreta disposal increased from 12.7 kg P
ha-1 in 1985 to 23.7 kg P ha-1 in 2005.
as a result, residual P associated with agriculture declined from
165.8 kg P ha-1 in 1985 to 129.1 kg P ha-1
in 2005. Phosphate utilization efficiency increased from 15.7%
in 1985 to 20.1% in 2005. Median, minimum and maximum values of
P flows by region showed similar trends. Phosphate input and withdrawal
through crop production by region were not related to regional
nitrogen (N) input and withdrawal through crop production. although
non-utilized P associated with agriculture has declined nationally
and regionally, it is still higher than that in foreign countries,
because of high chemical P fertilizer inputs and low crop yield
withdrawal. Because soil P fertility was often sufficiently high
previous large P surpluses, reducing P applications did not affect
crop yields. Crop P uptake was less than half that of crop N yield.
These results indicate that P inputs, especially by chemical fertilizer,
for crop production could be reduced, thereby reducing negative
environmental effects such as eutrophication of soil and water
and conserving limited P resources.
Keywords: Phosphate; Balance; Surplus; National; Region』
Introduction
Method
Framework
Chemical fertilizer application
Livestock excreta use and disposal
Crop P uptake
Phosphate balance, residual P and P efficiency
Results and discussion
Chemical fertilizer and manure use
Crop P uptake
Phosphate balance and P efficiency
Livestock excreta disposal and residual P
Conclusion
References