Table 7.
Estimates of sediment and phosphorus loading of pasture streams from stream bank runoff, cattle feces, and stream bank erosion in 2008 and 2009.
| Item | Treatment† | Sediment | Phosphorus | ||||
|---|---|---|---|---|---|---|---|
| 2008 | 2009 | Cut‐banks‡ | 2008 | 2009 | Cut‐banks‡ | ||
| kg | g | ||||||
| Runoff§ | CSU | 554.72 | 257.04 | – | 1122.26 | 812.45 | – |
| CSR | 55.47 | 8.67 | – | 179.62 | 59.59 | – | |
| RS | 371.91 | 82.02 | – | 933.59 | 343.08 | – | |
| Cattle feces¶ | CSU | 267.98# | 298.61 | – | 1795.48 | 1884.47 | – |
| CSR | 41.35 | 77.64 | – | 256.07 | 476.90 | – | |
| RS†† | 0 | 25.59 | – | 0 | 147.09 | – | |
| Net erosion | ×103 | ||||||
| Grazing season | CSU | 85.84 | 37.95 | 54.87 | 20.33 | 9.16 | 13.29 |
| CSR | 84.92 | −4.11 | 13.78 | 21.03 | −0.29 | 2.85 | |
| RS | 188.25 | 30.40 | 49.96 | 42.22 | 7.95 | 9.59 | |
| Winter | CSU | 49.12 | 170.08 | 412.26 | 11.47 | 42.90 | 99.80 |
| CSR | 11.10 | 89.75 | 97.09 | 2.63 | 23.49 | 19.87 | |
| RS | 136.28 | 98.07 | 131.36 | 25.66 | 21.95 | 28.66 | |
CSR, continuous stocking with restricted stream access; CSU, continuous stocking with unrestricted stream access; RSU, rotational stocking.
Amounts estimated to be lost from transects located on cut‐banks in 2009.
Runoff data include precipitation occurring from 1 May to 31 Oct. 2008 and from 1 Apr. to 31 Oct. 2009. Precipitation data for April 2009 were retrieved from NOAA weather station in Marshalltown, Iowa (∼15 mi from study site). Based on 141‐m stream reach of site pastures with a 4.6‐m bank height.
Based on 15 cows stocked on a 12.1‐ha pasture.
Total feces deposited into stream.
Cattle were not stocked in the riparian area at the same time as location determination except for September 2009.