Influence of streambank fencing and river access for cattle on riparian zone soils adjacent to the Lower Little Bow River in southern Alberta, Canada

Miller, J. J., Curtis, T., Chanasyk, D. S. and Willms, W. D. 2014. Influence of streambank fencing and river access for cattle on riparian zone soils adjacent to the Lower Little Bow River in southern Alberta, Canada. Can. J. Soil Sci. 94: 209–222. Cattle grazing in riparian pastures adjacent to rivers may increase soil compaction and increase soil nutrients, such as N and P. We conducted a 4-yr study with sampling in 3 yr (2009, 2010, 2012) of riparian zone soils adjacent to fenced and unfenced reaches of the Lower Little Bow River in southern Alberta. We examined the effect of grazing, access of cattle to the river (access versus no-access), and distance (0.25, 1, 2, 4, 6, 8, 10 m) from the river on surface soil bulk density, volumetric water content, NH₄-N, NO₃, and soil test P. Penetration depth was also measured in 2012. The three grazing treatments consisted of one fenced reach (ungrazed treatment), one unfenced and grazed reach with high cattle impact (high-impact grazed treatment), and one unfenced and grazed reach with low cattle impact (low-impact grazed treatment). We hypothesized that soil compaction would be greater, soil nutrients would be enriched, and soil water content would be lower for grazed compared with ungrazed treatments, and that this same trend would occur for access compared with no-access locations. The soil properties in our study were generally significantly (P≤0.05) influenced by grazing, access, and distance from the riverbank. However, treatment effects were generally dependent on two- or three-way interactions with the other factors. Soil bulk density in 2009 and 2012 was 8 to 20% greater at access compared with no-access locations within 2 m of the riverbank, suggesting soil compaction by cattle was confined close to the wetter riverbank soils. Most soil properties generally supported our hypothesis of greater soil compaction and nutrient enrichment for unfenced compared with fenced reaches, as well as for access compared with no-access locations. The exceptions were soil water content and soil test P results that did not support the grazing hypothesis, and soil water content and NH₄-N results that did not support the cattle-access hypothesis.