Estimates presented here are based upon the latest information from the National Resources Inventory (NRI). The NRI is a longitudinal sample survey based upon scientific statistical principles and procedures. It is conducted by the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS), in cooperation with Iowa State University’s Center for Survey Statistics and Methodology. These results are based upon the 2007 NRI, which provides nationally consistent data for the 25-year period 1982–2007. Estimates here cover the contiguous 48 states. Separate estimates include Hawaii, Alaska, and the Caribbean.
Margins of error are reported for each NRI estimate and must be considered at all scales of analysis. The margin of error is used to construct the 95 percent confidence interval for the estimate. The lower bound of the interval is obtained by subtracting the margin of error from the estimate; the upper bound is obtained by adding the margin of error to the estimate. A 95 percent confidence interval means that in repeated samples from the same population, 95 percent of the time the true underlying population parameter will be contained within the lower and upper bounds of the interval. In the following tables, if there are instances where the margin of error is greater than or equal to the estimate, they are displayed in italics indicating that the confidence interval includes zero and the estimate should not be used.
Table 18. Water (Sheet & Rill) Erosion on Cropland, by Year, with Margins of Error
Year
Million Tons per Year
Tons per Acre per Year
1982
1,676.5
±13.3
4.0
±0.0
1987
1,488.2
±10.6
3.7
±0.0
1992
1,179.6
±9.4
3.1
±0.0
1997
1,039.5
±7.2
2.8
±0.0
2002
1,011.1
±12.7
2.8
±0.0
2007
959.9
±14.9
2.7
±0.0
Notes:
• Cropland includes cultivated and non-cultivated cropland.
• Estimated margins of error <.05 are shown as 0.0.
Table 19. Wind Erosion on Cropland, by Year, with Margins of Error
Year
Million Tons per Year
Tons per Acre per Year
1982
1,384.5
±28.9
3.3
±0.1
1987
1,304.5
±25.1
3.2
±0.1
1992
994.5
±24.2
2.6
±0.1
1997
846.4
±19.2
2.3
±0.0
2002
802.0
±28.4
2.2
±0.1
2007
765.1
±37.8
2.1
±0.1
Notes:
• Cropland includes cultivated and non-cultivated cropland.
• Estimated margins of error <.05 are shown as 0.0.
Table 20. Highly Erodible (HEL) Cropland and Non-Highly Erodible (Non-HEL) Cropland, by Year, in Millions of Acres, with Margins of Error
Year
HEL Cropland Eroding At or Below Soil Loss Tolerance Rates
HEL Cropland Eroding Above Soil Loss Tolerance Rates
Total HEL Cropland
Non-HEL Cropland Eroding At or Below Soil Loss Tolerance Rates
Non-HEL Cropland Eroding Above Soil Loss Tolerance Rates
Total Non-HEL Cropland
1982
41.4
±0.9
83.9
±1.0
125.3
±1.2
209.6
±1.7
84.7
±1.2
294.3
±1.8
1987
38.7
±0.9
79.0
±0.9
117.7
±1.2
209.3
±1.5
78.5
±1.0
287.8
±1.8
1992
41.2
±0.8
64.8
±1.0
106.0
±1.2
215.2
±1.5
60.3
±1.0
275.4
±1.8
1997
46.7
±1.0
57.9
±0.8
104.6
±1.2
220.8
±1.5
50.7
±0.8
271.5
±1.8
2002
45.1
±1.2
56.1
±1.5
101.2
±1.5
216.9
±1.9
49.0
±0.9
265.9
±2.1
2007
44.1
±1.3
53.6
±1.4
97.8
±1.7
213.7
±2.4
45.6
±1.5
259.3
±2.6
Notes:
• Cropland includes cultivated and non-cultivated cropland.
Table 21. Erosion on Highly Erodible (HEL) Cropland and Non-Highly Erodible (Non-HEL) Cropland, by Year, in Millions of Tons per Year, with Margins of Error
Year
Highly Erodible (HEL) Cropland
Non-Highly Erodible (Non-HEL) Cropland
Erosion on Land Eroding At or Below Soil Loss Tolerance Rates (T)
Erosion on Land Eroding Above Soil Loss Tolerance Rates (T)
Erosion on Land Eroding At or Below Soil Loss Tolerance Rates (T)
Erosion on Land Eroding Above Soil Loss Tolerance Rates (T)
Erosion at T
Erosion above T
Total Erosion
Erosion at T
Erosion above T
Total Erosion
1982
79.5
±2.1
344.1
±4.4
1,322.1
±22.9
1,666.2
±24.6
504.5
±4.5
388.6
±5.7
422.1
±9.1
810.7
±14.1
1987
74.3
±2.1
326.2
±4.0
1,146.6
±19.1
1,472.9
±21.1
484.4
±4.3
361.6
±4.8
399.5
±9.2
761.1
±13.2
1992
76.5
±2.2
267.6
±4.5
805.3
±21.2
1,072.9
±23.1
476.3
±3.5
277.3
±4.9
271.0
±4.4
548.4
±8.5
1997
87.7
±2.2
238.0
±3.7
640.4
±17.4
878.4
±19.4
455.4
±4.0
233.5
±3.9
230.9
±5.4
464.4
±8.4
2002
82.1
±3.4
232.5
±6.2
616.0
±29.4
848.5
±33.4
438.6
±5.8
226.3
±4.3
217.6
±8.2
443.9
±11.5
2007
78.7
±3.0
223.1
±6.7
595.1
±35.5
818.3
±39.7
418.3
±6.3
210.4
±6.9
199.3
±10.0
409.7
±16.3
Notes:
• Cropland includes cultivated and non-cultivated cropland.
