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. 2009. Root mass for oilseed and pulse crops: Growth and distribution in the soil profile. Can. J. Plant Sci. 89: 883Á893. Crop roots transport water and nutrients to the plants, produce nutrients when they decompose in soil, and provide organic C to facilitate the process of C sequestration in the soil. Many studies on these subjects have been published for cereal crops, but little is known for oilseed and pulse crops. This study was conducted at Swift Current, Saskatchewan, in 2006 and 2007 to characterize the root growth and distribution profile in soil for selected oilseed and pulse crops. Three oilseed [canola (Brassica napus L.), mustard (Brassica juncea L.), flax (Linum usitatissimum L.)], three pulse crops [chickpea (Cicer arietinum L), dry pea (Pisum sativum L.) lentil (Lens culinaris Medik.)], and spring wheat (Triticum aestivum L.) were grown in 100 cm deep )15 cm diameter lysimeters pushed into a silt loam soil. Crops were studied under rainfed and irrigated conditions. Lysimeters were removed from the field and sampled for above-ground (AG) and root mass at different depths at five growth stages. Root mass was highest for canola (1470 kg ha(1 ) and wheat (1311 kg ha ). The root mass of oilseeds and pulses reached a maximum between late-flowering and late-pod stages and then decreased to maturity, while wheat root mass decreased to maturity after reaching a maximum at boot stage. On average, about 77 to 85% of the root mass was located in the 0 (40 cm depth. Canola, mustard, and wheat rooted to 100 cm, while the pulses and flax had only 4 to 7% of the root mass beyond the 60 cm depth. Irrigation only increased root mass in the 0Á20 cm depth. Roots developed more rapidly than AG biomass initially, but the ratio of root biomass to AG biomass decreased with plant maturity. At maturity, the ratio of root biomass to AG biomass was 0.11 for dry pea, and between 0.20 and 0.22 for the other crops tested. Our findings on rooting depths and root mass distribution in the soil profile should be useful for modelling water and nutrient uptake by crops, estimating C inputs into soil from roots, and developing diverse cropping systems with cereals, oilseeds and pulses for semiarid environments. Les cultures ont e´te´e´tudie´es sous re´gime pluvial et sous irrigation. Les lysime`tres ont e´te´retire´s du champ, puis on les a e´chantillonne´s afin de mesurer la masse des organes ae´riens et celle des racines a`diverses profondeurs, a`cinq stades de croissance. Ce sont le canola et le ble´qui enregistrent la plus forte masse racinaire (1 470 kg et 1 311 kg par hectare, respectivement). Suivent la moutarde (893 kg par hectare) et le pois chiche (848 kg par hectare), le pois et le lin arrivant bon derniers (524 kg et 440 kg par hectare, respectivement). La masse racinaire des ole´agineux et des le´gumineuses atteint un maximum entre la fin de la floraison et la fin de la production des gousses. Ensuite, elle diminue jusqu'a`ce que la plante parvienne a`maturite´. En revanche, la masse racinaire du ble´commence a`diminu...

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M. 2008. Nitrogen mineralization under summer fallow and continuous wheat in the semiarid Canadian prairie. Can. J. Soil Sci. 88: 681Á696. The ability of soils to provide a portion of the N required by crops via N mineralization of organic matter is of economic and environmental importance. Over a 40-yr period (1967Á2006), soil NO 3 -N and plant-N measurements were made under summer fallow and in systems cropped to spring wheat (Triticum aestivum L.), on a medium-textured Orthic Brown Chernozem (Aridic Haploboroll), at Swift Current, Saskatchewan. These values were used to estimate net N mineralization (N min ). Each year, above-ground plant N was measured at harvest and soil NO 3 -N was measured before seeding, soon after harvest, and just prior to freeze-up in October. Also, in the first 18 yr of this study NO 3 -N and aboveground plant N were measured eight times between spring and fall in selected treatments; these data were used to make a more detailed estimate of N min. In a third experiment, conducted on the same soil at a nearby site in 1975, many small lysimeters were sampled six times between spring and harvest of spring wheat. We used this lysimeter study to assess the effect of N fertilizer rate and soil water on net N min. Results from the more frequent sampling were more plausible than those from sampling at three different times per year. On average, net N min in the 20-mo summer fallow period was about 118 kg ha(1 (15 kg ha (1 between harvest and the first spring, 93 kg ha (1 between the first spring and second fall, and 10 kg ha(1 between the second fall and seeding). The average net N min under a wheat crop between spring and fall was between 53 and 63 kg ha (1 . Net N min increased with water, but excessive water appeared to reduce apparent net N min , probably due to leaching and denitrification losses of N, which were not assessed in our estimation of N min . Regression analysis was used to show a positive association between net N min and precipitation, between spring and fall, for most of the systems examined. There was evidence that tillage promotes N mineralization. At normal rates of N fertilizer (i.e., B 100 kg ha(1 ), fertilizer had no effect on N min . Net N min was directly proportional to fallow frequency, averaging 68, 83, and 90 kg ha(1 yr (1 for continuous wheat, fallow-wheat-wheat, and fallow-wheat rotations, respectively. Although our results may only be applicable to medium-textured soils of similar organic matter content in the Brown and Dark Brown Chernozemic soil zone, they provide data and information against which process-based models can be tested. They also provide useful first approximations of N min measured under field conditions where few long-term data currently exist.Key words: N mineralization, plant-N, fertilizer-N, crop rotation, irrigation, tillage Campbell, C. A., Zentner, R. P., Basnyat, P., DeJong, R., Lemke, R., Desjardins, R. et Reiter, M. 2008.Mine´ralisation de l'azote sur jache`re estivale et monoculture du ble´dans les prairies semi-arides du Canada...