Reynolds, W. D., Drury, C. F., Yang, X. M., Tan, C. S. and Yang, J. Y. 2014. Impacts of 48 years of consistent cropping, fertilization and land management on the physical quality of a clay loam soil. Can. J. Soil Sci. 94: 403â419. Soil physical quality (SPQ) is often ignored or under-monitored in long-term field studies designed to determine the economic and environmental sustainability of agricultural practices. Accordingly, a suite of complementary soil physical and hydraulic parameters was measured using intact core samples to determine the SPQ of a Brookston clay loam under a long-term (48 yr) cropping, fertilization and land management study at Woodslee, Ontario. The SPQ under virgin woodlot, fertilized monoculture sod and unfertilized monoculture sod treatments was similar, with optimal SPQ occurring in the top 10â20 cm, but severely suboptimal SPQ occurring below 30 cm because bulk density (BD), relative field capacity (RFC) and saturated hydraulic conductivity (KS) were excessive, and because organic carbon (OC), air capacity (AC) and plant-available water capacity (PAWC) were critically low. The SPQ for fertilized and unfertilized monoculture corn under fall moldboard plow tillage was similar and substantially suboptimal throughout the top 40â50 cm due to high or excessive BD and RFC, critically low OC, low or critically low AC and PAWC, and KS that varied erratically from excessive to critically low. The SPQ under fertilized and unfertilized cornâoatâalfalfaâalfalfa rotations (corn and second-year alfalfa fall plowed) was similar and largely non-optimal below 10 cm, but largely optimal in the top 10 cm due to the ameliorating effects of numerous biopores and crop roots. A bimodal soil water release function fitted to release curve data showed that PAWC was determined by soil matrix porosity (PM), and AC was determined by soil structure porosity (PS). Strong inverse linear correlations between BD vs. PM, BD vs. PS and BD vs. OC provided site-specific estimates of optimal ranges and critical limits for PAWC, AC and OC, respectively. Although SPQ changed substantially among treatments, the changes did not extend below 30-to 40-cm depth, and were largely unaffected by long-term annual fertilization. The SPQ below 30- to 40-cm depth was similarly poor across all treatments, and is likely an inherent characteristic of the soil.
Auteurs et éditeurs
On June 2, 1920, the Canadian Society of Technical Agriculturists was formally launched. The idea of an organization dedicated to the professional aspects of Canadian agriculture caught on and branches quickly formed across the country.
By 1944 the Canadian Society of Technical Agriculturists had evolved into the Agricultural Institute of Canada. Over time, nine provincial institutes of agrologists came on board to administer the formation, recognition and control of professional groups under provincial jurisdiction.