Addition of switchgrass (Panicum virgatum) barriers to vegetative filter strips (FS) shows potential as conservation practice. This study evaluates the comparative effectiveness of three conservation practices in reducing runoff, sediment, N, and P losses from 1.5‐ by 16‐m plots on an Aeric Epiaqualf. Three practices compared are a traditional fescue (Festuca arundinacea) filter strip (Fescue‐FS), a switchgrass barrier in combination with the Fescue‐FS (B‐Fescue‐FS) and a switchgrass barrier in combination with a native grass and forbs species filter strip (B‐Native‐FS). This study also predicts transport of sediment, N, and P in Fescue‐FS and B‐Fescue‐FS. Fescue‐FS and B‐Fescue‐FS of equal widths (0.7 m) significantly reduced runoff and sediment transport as compared with a continuous cultivated fallow (CCF) treatment, but B‐Fescue‐FS was more effective for reducing runoff (p < 0.05) and sediment (p < 0.01) transport. B‐Fescue‐FS was also more effective than Fescue‐FS for reducing losses of organic N, NO3–N, NH4–N, particulate P, and PO4–P (p < 0.01). Fescue‐FS and B‐Native‐FS were equally effective for reducing runoff, sediment, and nutrient loss. Effectiveness of FS increased with distance with 18% of runoff, 92% of sediment, and 71% of nutrient leaving the source area being reduced in the first 4 m of the FS. An equation to predict sediment associated with runoff ponding above barriers explained approximately 70% of the variability between measured and predicted values of sediment, organic N, and particulate P transport. Combination of switchgrass barriers with FS is an effective alternative to Fescue‐FS alone for reducing sediment and nutrients in runoff.

This research assessed the occurrence of hydroxylated atrazine degradation products (HADPs) in streamwater from Goodwater Creek watershed in the claypan soil region of northeastern Missouri. Streamwater was sampled weekly from June 1992 to December 1994 at a V-notch weir used to measure streamflow for this 7250-ha watershed. Filtered water samples were prepared by cation exchange solidphase extraction and analyzed for hydroxyatrazine (HA), deethylhydroxyatrazine (DEHA), and deisopropylhydroxyatrazine (DIHA) by high-performance liquid chromatography with UV detection. HADPs were confirmed by mass spectrometry and an alternative HPLCNV method. Frequency of HADP detection was 100% for HA, 25% for DEHA, and 6% for DIHA. Concentrations ranged from 0.18 to 5.7 p g L-l for HA, from <0.12 to 1.9pg L-' for DEHA, and from '0.12 to 0.72pg L-l for DIHA. These results establish that HADPs can contaminate surface water and that HA contamination of surface water is a significant fate pathway for atrazine in this watershed.

The effectiveness of stiff‐stemmed grass hedge systems in controlling runoff and soil erosion is influenced by the water transport properties of the soil under grass hedge management. This study evaluated soil hydraulic properties within a grass hedge system 10 yr after establishment. The study was conducted at the USDA‐ARS research station near Treynor, IA in a field managed with switchgrass (Panicum virgatum) hedges. The soil was classified as Monona silt loam (fine‐silty, mixed, superactive, mesic Typic Hapludolls). Three positions were sampled: within the grass hedges, within the deposition zone 0.5 m upslope from the grass hedges, and within the row crop area 7 m upslope from the hedges. Intact soil samples (76 by 76 mm) were taken from the three positions at four depths (100‐mm increments) to determine saturated soil hydraulic conductivity (Ksat), bulk density (ρb), and soil water retention. The grass hedge position had significantly greater (P < 0.05) macroporosity than the row crop and deposition positions in the first two depths and greater than the deposition position in the last two depths. The Ksat within the grass hedge (668 mm h−1) was six times greater than in the row crop position (115 mm h−1) and 18 times greater than in the deposition position (37 mm h−1) for the surface 10 cm. Bulk density and macroporosity were found to provide the best two‐parameter regression model for predicting the log‐transformed Ksat (R2 = 0.68). These results indicate that grass hedges significantly affected soil hydraulic properties for this loess soil.

Saturated hydraulic conductivity (K...) is an essential parameter for understanding soil hydrology. This study evaluated the K... of in situ monoliths and intact cores and compared the results with other studies for Missouri claypan soils. These K... values were used as runoff. model inputs to assess the impact of K... variation on simulated runoff. Lateral in situ K... of the topsoil was determined on 250 by 500 by 230 mm deep monoliths. These values were compared with the K.., of 76 by 76 mm diam. intact cores with and without bentonite to seal macropores. Mean

Iwara A.I. (2014): Evaluation of the variability in runoff and sediment loss in successional fallow vegetation of Southern Nigeria. Soil & Water Res., 9: 77-82. The effects of three different ages of natural fallow vegetation on runoff and sediment loss were investigated in a part of the rainforest zone of Nigeria. Measurements of runoff amount and sediment loss were made for the months of March to November in 2012 rainy season using runoff plots of 40 m 2. The average runoff amount for the 5-year-old, 3-year-old, and farmland plots were 0.47, 0.26, and 0.41 mm respectively. The average sediment loss on the 5-year-old, 3-year-old, and farmland plots were 209.24, 50.54, and 124.68 kg/ha, respectively. The lowest losses for both runoff and sediment were recorded on the 3-year-old plot, while the 5-year-old plot experienced the highest losses. The variations in runoff and sediment loss among the treatments were significant at P < 0.001. The results evidently showed that rainfall was principally responsible for the erosional losses on all the fallow treatments, and that ground cover (density of herbs) and girth helped to reduce sediment loss on the 3-year-old and farmland surfaces, respectively. The high amount of erosional losses experienced on the 5-year-old fallow than on the 3-year-old fallow and farmland plots imply that fallow that is not adequately protected by ground cover experiences accelerated soil erosion. The continuous loss in topsoil rich in plant nutrients may prolong the optimal capacity of the soil to regain its loss nutrient for subsequent food crop cultivation.