Agriculture Reference
In-Depth Information
Although the coeffi cients of determination R
2
is relatively weak, the
model is statistically signifi cant. The model suggests that natural factors
act as sinks, and as the input intensity of natural factors including rainfall
and sunlight inside the contributing zone (Zone 1) increases, NO
3
-N lev-
els downstream decrease. In addition, several artifi cial inputs, especially
chemical fertilizer input, are identifi ed as the second largest contributors
of NO
3
-N, and as chemical fertilizer input intensity within the contributing
zone (Zone 1) increases, NO
3
-N levels downstream also increase.
TABLE 9:
Multiple regression model of NO
3
-N.
Scales
Variable in
equation
Standardized
Beta
R
2
Sig.
Number of
samples
Zone1
WI-IPC
1
−0.469
0.374
0.004
27
WI-IPC
2
0.412
Zone2
no variables were entered
17
Zone3
no variables were entered
14
Zone4
no variables were entered
10
Zone5
no variables were entered
8
TABLE 10:
Multiple regression model of COD
Mn
.
Scales
Variable in
equation
Standardized
Beta
R
2
Sig.
Number of
samples
Zone1
no variables were entered
27
Zone2
no variables were entered
17
Zone3
no variables were entered
14
Zone4
no variables were entered
10
Zone5
WI-IPC
3
0.527
0.452
0.001
8
WI-IPC
4
0.085
For the water quality index COD
Mn
, no variables were entered in the
stepwise regression analysis for the scales from Zone 1 to Zone 4, while
the most important explanatory variables were the WI-IPC
3
and WI-IPC
4
