Table 10. Pearson correlation coefficients among 1992 export, inputs, and other factors
[n, number of observations in the correlation data set; --, not estimated; **, correlation significant (p-value < 0.05); sites with known natural source of phosphorus (excluded from n = 5 data set) are sites 5, 6, and 10 (Duck River at Williamsport, Duck River above Hurricane Mills, and Elk River near Prospect, respectively)]
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Correlation coefficient (r)
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Input, land use, or other factor Total nitrogen export (n = 11) Total phosphorus export
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Excluding sites with
All sites (n = 8) known natural source (n = 5)
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Wastewater discharge 0.06 -0.24 0.97**
Atmospheric deposition .29 -- --
Fertilizer application .17 -.27 .94**
Livestock waste .57 .40 -.06
Balance of agricultural land-phase inputa .65** -.14 .70
Percent forest land -.41 -.06 -.80
Percent cultivated land .14 -.42 .82
Percent pasture land .67** .46 .85
Percent urban land .18 -.04 .90**
Site type (riverine = 1, flow-regulated = 2) -.58 -.52 -.53
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a Calculated for nitrogen as the sum of inputs from fertilizer application and nitrogen fixation and
livestock waste, minus removal as crop harvest; calculated for phosphorus as the sum of inputs from fertilizer
application and livestock waste, minus removal as crop harvest.
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