Individual study: Evaluation of Buffers to Improve the Quality of Runoff from Irrigated Pastures
Tate K.W., Nader G.A., Lewis D.J., Atwill E.R. & Connor J.M. (2000) Evaluation of Buffers to Improve the Quality of Runoff from Irrigated Pastures. Journal of Soil and Water Conservation, 55, 473-478
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Water: Plant buffer strips
A replicated, randomized, controlled study in 1997 in irrigated pastures in the foothills of the Sierra Nevadas, California, USA, found less sediment in runoff from pastures with buffers. Water availability: Similar amounts of water were lost as runoff from plots with or without buffers (118–1,386 vs 121–893 m3/ha). Nutrients: Similar amounts of nitrate and phosphorus were found in runoff from pastures with or without buffers (sprinkler: 1.78 vs 1.76 kg NO3-N/ha; 0.34 vs 0.38 kg total P/ha; flood: 0.91 vs 1.34 kg NO3-N/ha; 0.24 vs 0.23 kg total P/ha). Sediments: Less sediment was found in runoff from pastures with buffers, compared to pastures without buffers, in two of four comparisons (0.3 vs 0.4–0.16 g total suspended solids/litre). Methods: Buffers (10 m width, parallel to the stream channel or runoff ditch in which runoff was measured) were fenced to exclude grazers on 1 May 1997. Pastures and buffers were 40% clover and 60% grass. Four pastures had buffers, and four did not. Half of the pastures (1 ha each) were intensively sprinkler-irrigated and grazed (six cattle, five-day rotation). The other half (3 ha each) were flood-irrigated and grazed (20 cattle, seven-day rotation). The cattle were yearling beef heifers, in rotation from 1 June to 15 October. Runoff was measured during irrigation events (sprinkler: five events, 787 m3/ha/event; flood: eight events, 1,642 m3/ha/event) in August, September, and October (volume was measured every 15 minutes in a weir; samples were collected every hour).