T. Curtis

Influence of Streambank Fencing on the Environmental Quality of Cattle-Excluded Pastures

Limited information exists on the effect of streambank fencing on riparian zone pastures. The objective of this study was to test the hypothesis that 4 to 6 yr of streambank fencing would improve the environmental quality of the cattle-excluded pasture compared with the grazed pasture and cause the fenced pasture to act as a buffer or filter strip. Rangeland health, vegetative and soil properties, and rainfall simulation runoff were measured in the cattle-excluded and adjacent grazed native pastures along the fenced reach of the Lower Little Bow River in southern Alberta, Canada, for 3 yr (2005-2007). Rangeland health was improved (health score increase from 55 to 72%); vegetation cover (13-21%) and standing litter (38-742%) were increased; and bare soil (72-93%) and soil bulk density (6-8%) were decreased under cattle exclusion, indicating an improvement in environmental quality from streambank fencing. In contrast, other vegetation (total and live basal area, fallen litter) and soil properties (soil water and soil C, N, and P) were not improved by cattle exclusion. Cattle exclusion significantly (P </= 0.10) reduced surface runoff depth of water (21-32%) and mass loads of total N fractions (21-52%) in 2 of 3 yr compared with the grazed pasture, suggesting that this fenced pasture may act as a buffer for certain runoff variables. In contrast, other runoff variables (turbidity, electrical conductivity, pH, concentrations and loads of total suspended solids, and certain N and P fractions) in the cattle-excluded pasture were generally not improved by streambank fencing. Overall, streambank fencing improved the quality of certain environmental variables within the cattle-excluded pasture.

Phosphorus and nitrogen in runoff after phosphorus- or nitrogen-based manure applications.

Application of beef cattle () manure based on nitrogen (N) requirements of crops has resulted in elevated concentrations of soil test phosphorus (P) in surface soils, and runoff from this cropland can contribute to eutrophication of surface waters. We conducted a 3-yr field study (2005-2007) on a Lethbridge loam soil cropped to dryland barley () in southern Alberta, Canada to evaluate the effect of annual and triennial P-based and annual N-based feedlot manure on P and N in runoff. The manure was spring applied and incorporated. There was one unamended control plot. A portable rainfall simulator was used to generate runoff in the spring of each year after recent manure incorporation, and the runoff was analyzed for total P, total dissolved P, total particulate P, dissolved reactive P, total N, total dissolved N, total particulate N, NO-N, and NH-N. Annual or triennial P-based application resulted in significantly ( ≤ 0.05) lower (by 50 to 94%) concentrations or loads of mainly dissolved P fractions in runoff for some years compared with annual N-based application, and this was related to lower rates of annual manure P applied. For example, mean dissolved reactive P concentrations in 2006 and 2007 were significantly lower for the annual P-based (0.12-0.20 mg L) than for the annual N-based application (0.24-0.48 mg L), and mean values were significantly lower for the triennial P-based (0.06-0.13 mg L) than for the annual N-based application. In contrast, other P fractions in runoff were unaffected by annual P-based application. Our findings suggested no environmental benefit of annual P-based application over triennial P-based application with respect to P and N in runoff. Similar concentrations and loads of N fractions in runoff for the P- and N-based applications indicated that shifting to a P-based application would not significantly influence N in runoff.

Physical and chemical properties of feedlot pen surfaces located on moderately coarse- and moderately fine-textured soils in southern Alberta.

Southern Alberta has the highest density of feedlot cattle in Canada, and there is a concern that leaching of water and contaminants may be greater for feedlots located on coarser-textured than finer-textured soils. Our objective was to determine if infiltration and leaching were greater for a 4-yr-old feedlot located on a moderately coarse-textured (MC) soil compared with two feedlots located on moderately fine-textured (MF) soils (5- and 52-yr-old pens). Various soil physical properties of feedlot pen surfaces were measured, including field-saturated hydraulic conductivity (K(fs)) and near-saturated hydraulic conductivity at -0.9 and -3.9 cm water potential. Selected chemical properties of feedlot soil layers were measured, as well as the chloride content of the soil profile (0-100 cm). Mean K(fs), K(-0.9), and K(-3.9) values were not significantly (P > 0.10) greater at the MC site than the two MF sites, indicating no evidence of greater infiltration on coarser-textured soils. In addition, mean K(fs), K(-0.9), and K(-3.9) values of soils within feedlot pens at all three sites were significantly (P < or = 0.10) reduced by 46 to 78% compared with soil outside the pens. Depth of chloride accumulation was greatest at the 52-yr-old feedlot on MF soil (60-70 cm), followed by 4-yr-old feedlot on MC soil (40-50 cm) and 5-yr-old feedlot on MF soil (30-40 cm). Visual inspection determined that the black interface layer formed within 2 mo of cattle stocking at all three sites.

Soil test phosphorus and nitrate adjacent to artificial and natural cattle watering sites in southern Alberta

Off-stream watering troughs may reduce surface water pollution by keeping nutrients away from natural water bodies, but may increase nutrient contaminant of groundwater. The objective of this study was to determine to what extent off-stream watering troughs active for 2 to 7 yr caused enrichment and leaching of soil test P (STP) and KCl-extractable NO3-N. The study was conducted in the Lower Little Bow (LLB) River watershed of southern Alberta, Canada. Soil samples were obtained at three recently installed off-stream watering troughs, four active cattle watering sites adjacent to the LLB River, and at two sites along a fenced reach of the river with no cattle access. At each location, samples were obtained along four 100-m transects. Surface (0-5 cm) soil immediately adjacent to the LLB River was not enriched in STP or NO3-N, which was attributed to flushing of nutrients during periods of high flow. Surface soil at distances ≤ 5 m from the three water troughs was approximately three times higher in STP th...

Influence of Organic Amendment and Compaction on Nutrient Dynamics in a Saturated Saline-Sodic Soil from the Riparian Zone.

Cattle grazing in wet riparian pastures may influence nutrient dynamics due to nutrient deposition in feces and urine, soil compaction, and vegetation loss. We conducted a lab incubation study with a saline-sodic riparian soil to study nutrient (N, P, S, Fe, Mn, Cu, and Zn) dynamics in soil pore water using Plant Root Simulator (PRS) probes and release of nutrients into the overlying ponded water during flooding. The treatment factors were organic amendment (manure, roots, and unamended control), compaction (compacted, uncompacted), and burial time (3, 7, and 14 d). Amendment treatment had the greatest impact on nutrient dynamics, followed by burial time, whereas compaction had little impact. The findings generally supported our hypothesis that organic amendments should first increase nitrate loss, then increase Mn mobility, then Fe mobility and associated release of P, and finally increase sulfate loss. Declines in nitrate due to amendment addition were small because nitrate was at low levels in all treatments due to high denitrification potential instead of being released to soil pore water or overlying water. Addition of organic amendment strongly increased Mn and Fe concentrations in overlying water and of adsorbed Fe on PRS probes but only increased Mn on PRS probes on Day 3 due to subsequent displacement from ion exchange membranes. Transport of P to overlying water was increased by organic amendment addition but less so for manure than roots despite higher P on PRS probes. The findings showed that saline-sodic soils in riparian zones are generally a nutrient source for P and are a nutrient sink for N as measured using PRS probes after 3 to 7 d of flooding.

Influence of Cattle Trails on Runoff Quantity and Quality

Cattle trails in grazed pastures close to rivers may adversely affect surface water quality of the adjacent river by directing runoff to it. The objective of this 3-yr study (2013-2015) in southern Alberta, Canada, was to determine if cattle trails significantly increased the risk of runoff and contaminants (sediment, nutrients) compared with the adjacent grazed pasture (control). A portable rainfall simulator was used to generate artificial rainfall (140 mm h) and runoff. The runoff properties measured were time to runoff and initial abstraction (infiltration), total runoff depth and average runoff rates, as well as concentrations and mass loads of sediment, N, and P fractions. Cattle trails significantly ( ≤ 0.10) decreased time to runoff and initial abstraction (26-32%) in the 2 yr measured and increased total runoff depth, runoff coefficients, and average runoff rates (21-51%) in 2 of 3 yr. Concentrations of sediment, N, and P fractions in runoff were not significantly greater for cattle trails than for control areas. However, mass loads of total suspended solids (57-85% increase), NH-N (31-90%), and dissolved reactive P (DRP) (30-92%) were significantly greater because of increased runoff volumes. Overall, runoff quantity and loads of sediment, NH-N, and DRP were greater for cattle trails compared with the adjacent grazed pasture, and hydrologic connection with cattle-access sites on the riverbank suggests that this could adversely affect water quality in the adjacent river. Extrapolation of the study results should be tempered by the specific conditions represented by this rainfall simulation study.

Effectiveness of soil in vegetated buffers to retain nutrients and sediment transported by concentrated runoff through deep gullies

Abstract: Little research has evaluated naturally vegetated buffers to retain pollutants in soil from concentrated runoff through deep (2-14 m) gullies. Soil enrichment in the flow path of 11 naturally vegetated gullies in southern Alberta, Canada, was used as a long-term signature of filtering during concentrated flow. Soil was sampled at three depth intervals (0-2.5, 2.5-5, and 5-10 cm) along two 50-m transects inside and outside the flow path of the vegetated gullies in each of 3 yr (2011-2013). The influence of soil type, flow path (inside vs. outside), distance into vegetated flow path, depth, and their interactions on enrichment of nutrients (NH4-N, NO3-N, soil test P (STP), total P) and particle size fractions (clay, silt, and sand) was determined. Significantly (P ≤ 0.05) greater enrichment of nutrients and specific particle size fractions inside than outside the flow path of the vegetated gully suggested that greater deposition occurred inside the concentrated flow path. In contrast, there was little evidence for enrichment of nutrients and sediment at the front or inlet of the buffer (except STP), or for infiltration of more soluble nutrients into the subsoil. Soil enrichment in buffers may reveal long-term filtering processes that may not be shown with short-term runoff experiments.

Influence of riparian grazing on channel morphology and riparian health of the Lower Little Bow River

Unmanaged riparian grazing may negatively impact rivers. The objective was to determine the influence of riparian grazing by cattle on selected channel morphology properties and riparian health of the Lower Little Bow River in southern Alberta. Three study reaches with increasing levels of riparian grazing impact were selected: (1) a fenced reach with cattle exclusion (2001–2012) followed by two years (2013–2014) of periodic grazing of the riparian pasture, (2) an unfenced and grazed reach with low cattle impact, and (3) an unfenced and grazed reach with high cattle impact. Selected channel morphology properties were measured for 3 years (2013–2015), and streambank erosion was measured over 6 years (2009–2014). The riparian health of the fenced reach was also assessed before and after 4, 8 and 11 yr of cattle exclusion, and then after 2 yr of periodic grazing. The findings generally supported the hypothesis that reduced or no riparian grazing impact would significantly (P ≤ 0.10) increase bank undercut, water depth, bankfull depth and mean-weight diameter of riverbed sediment, and decrease flow width, flow width:depth ratio, bankfull width, bankfull width:depth ratio and bank erosion. The overall riparian health score of the fenced reach was increased from 65% (healthy but with problems) prior to fencing to 85% (healthy) after 11 yr of cattle exclusion, but then decreased to 78% (healthy but with problems) after two years of periodic grazing. Exclusion fencing generally improved most channel morphology variables and riparian health. However, non-utilization of the forage resource, excess litter build-up and greater fire risk, and increased disturbance-caused plants and invasive species were serious management concerns. These issues might be alleviated by periodic grazing of the riparian pasture, but the long-term effect of this practice on channel morphology and riparian health requires further research.

Influence of streambank fencing on vegetation and soil of the Mixed prairie component in a complex corridor pasture

Abstract: A 5 yr (2011–2015) field study was conducted to test the hypothesis that streambank fencing had a significant effect on selected vegetation and soil properties of the Mixed prairie component of a complex corridor pasture. The grazing treatments [ungrazed (UG) – periodic grazing (PG)] inside the corridor pasture were 11 yr (2001–2012) of cattle exclusion (UG), followed by 3 yr (2013–2015) of periodic grazing (PG) when the riparian soil was dry. A control treatment outside the fencing was continuous grazing (CG). Selected vegetation and soil properties were measured over the growing season at 10 paired locations in each treatment (nonreplicated) pasture over 5 yr (2011–2015), and rangeland health was measured in 2011. The UG–PG treatment significantly (P ≤ 0.10) increased the total biomass by 2- to 5-fold in all 5 yr compared with CG treatment and improved the rangeland health score of the UG phase of the UG–PG (63%) treatment compared with the CG treatment (50%) in 2011. It also significantly reduced surface soil temperature by 2.2–5.2 °C, significantly increased volumetric water content of the surface soil by 7%–10% in 3 of 5 yr, and significantly increased surface soil CO2 efflux (instantaneous) by 17%–60% in all 5 yr. Overall, the UG–PG treatment improved rangeland health, increased total biomass, soil water, and soil CO2 efflux of the Mixed prairie, but decreased soil temperature compared with the CG treatment. Excessive dead biomass, greater fire risk, and an increase in noxious weeds caused by cattle exclusion suggested that periodic grazing may be the preferred option.