Temporal trends in soil properties at a soil quality benchmark site in the Lower Fraser Valley, British Columbia

Abstract

. 2002. Temporal trends in soil properties at a soil quality benchmark site in the Lower Fraser Valley, British Columbia. Can. J. Soil Sci. 82: 499-509. A national soil quality monitoring program was established in 1990 to address concerns that the quality of Canada's agricultural soils was in decline. The British Columbia benchmark site (01-BC) was established in 1991 and is located on the Pelly soil series (Orthic Humic Gleysol) supporting a corn-forage-pasture rotation in the Lower Mainland ecoregion. The objectives of this study were to report on the differences in: (1) the measured soil properties for the 5-yr period between baseline data collection in 1991 and resampling in 1996 and (2) the properties measured annually as indicators of soil compaction. A 25-m × 25-m grid was used at the site to locate sampling points for bulk density and collecting soil samples of the Ap, BCg, and Cg horizons, as well as the measurement locations for saturated hydraulic conductivity and penetration resistance. A 5-yr interval sampling regime was used to sample the Ap, BCg, and Cg horizons and bulk density. Saturated hydraulic conductivity and penetration resistance were sampled annually from 1992 to 1998. Between 1991 and 1996 in the A horizons, pH, available P, C:N ratio and bulk density increased by 4.6, 7.8, 2.5, and 8%, respectively, and available K, total C and total N decreased by 21, 16.5, and 18.3%, respectively. In the BCg horizon, pH, available P and C:N ratio increased by 5, 126, and 8%, respectively, and the available K and total N both decreased by 21%. Bulk density remained unchanged. The assumption that the soil chemical properties in the Cg horizon would remain stable during the study period did not hold. The trends detected for the Cg horizon were similar to those measured for the upper two horizons. However, only the reductions in available K and total N and increases in C:N were significant. The changes in the soil physical properties measured at this site indicate that some soil compaction has occurred. Both bulk density at 20 cm and penetration resistance increased at all depths between 1994 and 1998, which coincided with the time period that grazing was included in the crop rotation. Field saturated hydraulic conductivity at 25 cm (Ap2 horizon), although highly variable from year to year also tended to be lower during the pasture rotation. The penetration resistance measurements, which detected changes at all depths, appeared to be a more sensitive indicator of soil compaction than either bulk density or field saturated hydraulic conductivity.Key words: Soil quality, soil monitoring, soil properties, soil compaction, temporal change Kenney, E. A., Hall, J. W. et Wang, C. 2002. Évolution des propriétés pédologiques dans le temps à un site de contrôle de la qualité du sol dans la basse vallée du Fraser, en Colombie-Britannique. Can. J. Soil Sci. 82: 499-509. Face à la crainte d'une détérioration des sols agricoles au Canada, un programme national de contrôle de la qualité voyait le jour en 1990. L'année...

Soil and crop responses to long-term potato production at a benchmark site in northwestern New Brunswick

“…The 4% reduction in SOC from 1990 to 2000 (Table 4) is less than the 8% reduction in SOC reported by Rees et al (2007) from paired benchmark site 20-NB with up-and-down slope cultivation of potato over a comparable 10-yr period and considerably less than the reductions of 8 and 16% measured over 5-yr periods reported by Webb et al (2000) and Kenney et al (2002), respectively. The soils monitored by both Webb et al (2000) and Kenney et al (2002) had higher initial SOC concentrations than our benchmark site 22-NB, which had only 17.0 g kg (1 SOC in 1990, and so they may have had greater C losses by oxidation and mineralization than from our soil.…”

“…The soils monitored by both Webb et al (2000) and Kenney et al (2002) had higher initial SOC concentrations than our benchmark site 22-NB, which had only 17.0 g kg (1 SOC in 1990, and so they may have had greater C losses by oxidation and mineralization than from our soil. Climatic conditions varied as well.…”

“…As expected, there was no significant change in SOC level in the C horizon over the 10-yr period. Under conditions of a corn-forage-pasture in British Columbia, Kenney et al (2002) also identified changes in soil chemical properties of subsurface layers (BCg and Cg horizons at 50Á60 and 90Á120 cm, respectively). They found increases in subsoil pH and P and decreases in total C and K concentrations.…”

“…These results showing significant changes in available P and K are comparable with some other soil quality monitoring studies. For example, Kenney et al (2002) reported an 8% increase in available P but a 21% decrease in available K under a corn-foragepasture rotation in British Columbia. However, Webb et al (2000) reported a 13% decrease in available P over a similar 5-yr monitoring period of a corn-forage rotation in Nova Scotia.…”

“…The design of the AAFC soil quality monitoring benchmark system (Wang et al 1997) has been shown to be successful. Changes in soil chemical, physical and biological properties have been identified over 5-yr periods by Webb et al (2000) in Nova Scotia (benchmark site 19-NS) under a corn-forage rotation on a site consisting of Gleyed Brunisolic Gray Luvisols (Soil Classification Working Group 1998) and Gleyed Dystric Brunisols in the Annapolis-Minas Lowlands region, and by Kenney et al (2002) in British Columbia (benchmark site 01-BC) on Orthic Humic Gleysols supporting a corn-forage-pasture rotation in the Lower Mainland ecoregion. Both research groups found changes in some sensitive soil properties, such as SOC content, even over this short a period of time.…”