. 2008. Soil organic carbon and nitrogen pools as affected by compost applications to a sandy-loam soil in Quebec. Can. J. Soil Sci. 88: 443Á450. Compost contributes plant-available nutrients for crop production and adds partially decomposed carbon (C) to the soil organic carbon (SOC) pool. The effect of compost applications and other agricultural practices on SOC and total nitrogen (N) pools was determined in a sandy-loam Humic Gleysol at the Research Farm of McGill University, Ste-Anne-de-Bellevue, Quebec. Experimental plots with continuous silage corn (Zea mays L.) and silage corn-soybean (Glycine max L. Merr.) production were under conventional tillage (CT) or no-tillage (NT) management. Composted cattle manure was applied each spring at rates of 0, 5, 10 and 15 Mg (dry weight) ha(1 and supplemental NPK fertilizers were added to meet crop requirements. The C input from crop residues was affected by tillage, crop rotations and compost application, but differences in the SOC and total N pools were due to compost applications. After 5 yr, compost-amended plots gained 1.35 to 2.02 Mg C ha(1 yr (1 in the SOC pool and 0.18 to 0.24 Mg N ha(1 yr (1 in the total N pool, as compared with initial pool sizes when the experiment was initiated. These gains in SOC and total N were achieved with agronomic rates of compost and supplemental NPK fertilizers, selected to match the phosphorus requirements of silage corn. Such judicious use of compost has the potential to increase the SOC and total N pools in agroecosystems under annual crop production.

Irrigation practices change the soil moisture in agricultural fields and influence emissions of greenhouse gases (GHG). A 2 yr field study was conducted to assess carbon dioxide (CO2) and nitrous oxide (N2O) emissions from surface and subsurface drip irrigated tomato (Solanum lycopersicum L.) fields on a loamy sand in southern Ontario. Surface and subsurface drip irrigation are common irrigation practices used by tomato growers in southern Ontario. The N2O fluxes were generally ≤50 μg N2O-N m−2 h−1, with mean cumulative emissions ranging between 352 ± 83 and 486 ± 138 mg N2O-N m−2. No significant difference in N2O emissions between the two drip irrigation practices was found in either study year. Mean CO2 fluxes ranged from 22 to 160 mg CO2-C m2 h−1 with cumulative fluxes between 188 ± 42 and 306 ± 31 g CO2-C m−2. Seasonal CO2 emissions from surface drip irrigation were significantly greater than subsurface drip irrigation in both years, likely attributed to sampling time temperature differences. We conclude that these irrigation methods did not have a direct effect on the GHG emissions from tomato fields in this study. Therefore, both irrigation methods are expected to have similar environmental impacts and are recommended to growers.

, H. 2007. Monitoring corn and soybean agroecosystems after establishing no-tillage practices in Québec, Canada. Can. J. Plant Sci. 87: 841-849. The conversion to no-tillage (NT) may seem risky to some producers who rely on tillage to control weeds, some insect pests and disease-causing pathogens that can reduce crop yield. Weeds, arthropods, and disease incidence were monitored in silage corn (Zea mays L.) and soybean (Glycine max L. Merr.) agroecosystems with CT and newly established NT plots in Ste-Anne-de-Bellevue, Québec. During the first 2 establishment years, there were more annual grass and fewer annual broadleaf weeds in NT than in CT plots, but the surface area covered by weeds (broadleaf, grasses and perennials) was greater in CT than NT plots. Foliar arthropods were more numerous in soybean than corn plots in both years, but were unaffected by tillage. There were more ground-dwelling generalist predators, especially Coleoptera and Carabidae, in CT than NT plots, while spiders and harvestmen (Araneae and Opiliones) were dominant in NT plots. Crop damage from insect pests and diseases was below economic thresholds, but 5 yr of yield monitoring (2000)(2001)(2002)(2003)(2004) revealed a trend of greater silage corn and soybean yields in CT than NT plots. The reduction in crop yield after establishing NT practices at this site was probably due to rooting constraints from inadequate seedbed preparation in the NT system, rather than from weed competition, insect damage or crop diseases.Key words: Arthropods, crop disease, silage corn, soybean, tillage, weed control Whalen, J. K., Prasher, S. O. et Benslim, H. 2007. Surveillance aux agro-écosystèmes de maïs-ensilage et de soya convertis en semis-direct au Québec, Canada. Can. J. Plant Sci. 87: 841-849. Le système de semis-direct (NT) peut sembler risqué pour quelques producteurs qui comptent sur le labourage pour contrôler les mauvaises herbes, quelques insectes ravageurs et les pathogènes causant des maladies qui peuvent réduire la production végétale. Nous avons examiné des mauvaises herbes, des arthropodes, et l'incidence des maladies dans les agro-écosystèmes de maïs-ensilage (Zea mays L.) et soya (Glycine max L. Merr.), aux parcelles nouvellement converties en NT à Sainte-Anne-de-Bellevue, Québec. Pendant les deux premières années d'étab-lissement, il y avait plus des mauvaises herbes annuelles et moins des dicotylédones annuelles avec NT que dans les parcelles avec CT, mais le degré d'envahissement par les mauvaises herbes était plus grand dans le CT que le NT. Pendant deux ans, les arthropodes foliaires étaient plus nombreux en soya par apport au maïs-ensilage, mais ils n'étaient pas affectés par le labourage du sol. Il y avait plus de prédateurs de généraliste, particulièrement les coléoptères et les Carabidae, dans le CT que le NT, alors que les araignées et les faucheux (Araneae et Opiliones) étaient dominants dans les parcelles sous NT. La diminution du rendement de la récolte après l'établissement du NT sur ce site a été probablement due à la dif...

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<p>Earthworms create hotspots that support microbial diversity and activity in soil. These hotspots may be internal to the earthworm, such as in their intestinal tract, or external to the earthworm in the biopores, casts and middens they create on the soil surface and within the soil profile. This presentation summarizes some of the key hotspots associated with earthworms, and how the biostimulated microbial community in these areas contributes to soil nitrogen cycling. We will present observations about the diversity and activity of nitrogen-cycling microorganisms that live within the earthworm and in its built environments, as well as the population- and community-level contributions of earthworms to denitrification, nitrogen mineralization, and the soil nitrogen supply in temperate agroecosystems.</p>