Trace metal chemistry in arid-zone field soils amended with sewage sludge: I. Fraction-groves in relation to certain soil constituents.

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Pulse crops discussed in this review include soybean (Glycine max L.), dry pea (Pisum sativum L.), lentil (Lens culinaris Medik.), dry bean (Phaseolus vulgaris L.) and chickpea (Cicer arietinum L.). Basic maturity requirements, yield relationships with rainfall and temperature, relative yield comparisons, water relationships, water use efficiency (WUE), crop management, tillage systems, and the rotational impact of these crops on productivity were considered. With the exception of soybean, maturity requirements for pulse crops are met in most locations within the northern Great Plains. Yield was more closely related to growing season precipitation than maximum temperature for all pulse crops except dry bean and lentil. The inability to effectively relate weather parameters to dry pea and lentil yield may indicate broad adaptation of these two pulse crops within the northern Great Plains. Correlation analyses showed the productivity of chickpea, dry pea, and lentil to be most closely associated with each other and for dry bean productivity to be most closely associated with that of soybean, effectively grouping pulse crops into their respective cool‐ and warm‐season classifications. Dry pea and chickpea had high WUE values, similar to spring wheat (Triticum aestivum L.). Examination of plant water relations of these crops revealed an ability for chickpea and dry pea to grow at lower relative water contents than spring wheat. Increased wheat grain yield and/or protein following pulse crops under widely different N‐limiting growth conditions indicated a consistent N benefit provided by pulse crops to wheat. Four general research needs were identified. First, comparative adaptation among pulse crops remains poorly understood. Second, best management practices and key production risks remain incompletely characterized. Thirdly, the knowledge of rotational effects of pulse crops in the northern Great Plains remains imprecise and inadequate. Fourth, genetic improvement for early maturity, increased yield, improved harvestability, and disease resistance requires attention. Pulse crops are poised to play a much greater role in diversifying cropping systems in the northern Great Plains but require that these key research areas be addressed so that their production potential can be realized.

-J. 2006. A decade of herbicide-resistant crops in Canada. Can. J. Plant Sci. 86: 1243-1264. This review examines some agronomic, economic, and environmental impacts of herbicide-resistant (HR) canola, soybean, corn, and wheat in Canada after 10 yr of growing HR cultivars. The rapid adoption of HR canola and soybean suggests a net economic benefit to farmers. HR crops often have improved weed management, greater yields or economic returns, and similar or reduced environmental impact compared with their non-HR crop counterparts. There are no marked changes in volunteer weed problems associated with these crops, except in zero-tillage systems when glyphosate is used alone to control canola volunteers. Although gene flow from glyphosate-HR canola to wild populations of bird's rape (Brassica rapa L.) in eastern Canada has been measured, enrichment of hybrid plants in such populations should only occur when and where herbicide selection pressure is applied. Weed shifts as a consequence of HR canola have been documented, but a reduction in weed species diversity has not been demonstrated. However, reliance on HR crops in rotations using the same mode-of-action herbicide and/or multiple in-crop herbicide applications over time can result in intense selection pressure for weed resistance and consequently, greater herbicide use in the future to control HR weed biotypes. History has repeatedly shown that cropping system diversity is the pillar of sustainable agriculture; stewardship of HR crops must adhere to this fundamental principle. L'adoption rapide du canola et du soja RH laisse croire que les agriculteurs y trouvent un net avantage économique. Les cultures RH ont souvent facilité la lutte contre les mauvaises herbes, accru le rendement ou les revenus tout en ayant un impact similaire voire plus faible que les cultures qui ne le sont pas sur l'environnement. On ne remarque pas de changement marqué au niveau de la repousse spontanée des adventices avec ces cultures, sauf dans les systèmes de non-travail du sol où l'on n'utilise que du glyphosate pour combattre la repousse spontanée du canola. Bien qu'on ait mesuré la transmission de gènes du canola résistant au glyphosate aux populations sauvages de navette (Brassica rapa L.) dans l'est du Canada, l'enrichissement de ces populations par des hybrides ne survient que si l'herbicide accentue la pression sélective. La littérature scientifique cite des cas où la population d'adventices change consécutivement à la culture de canola RH, mais on n'a pu démontrer l'appauvrissement de la diversité des espèces. Employer des cultures RH dans les assolements où l'on recourt à des herbicides ayant le même mode d'action ou applique une multitude d'herbicides peut néanmoins déboucher avec le temps sur une intense pression sélective qui favorisera les adventices plus résistantes, ce qui nécessitera éventuellement un usage plus intense d'herbicides pour lutter contre les biotypes RH. L'histoire a montré à maintes reprises que la variété des systèmes agricoles est la pierre angulaire ...

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