Lemke, R. L., Izaurralde, R. C., Nyborg, M. and Solberg, E. D. 1999. Tillage and N source influence soil-emitted nitrous oxide in the Alberta Parkland region. Can. J. Soil Sci. 79: 15-24. Zero tillage systems are receiving attention as possible strategies for sequestering atmospheric carbon. This benefit may be offset by increased N 2 O emissions, which have been reported for soils under zero tillage (ZT) compared to those under more intensive tillage (IT). Comparisons of N 2 O emissions from the two systems have been restricted to the growing season, but substantial losses of N 2 O have been reported during spring thaw events in many regions. Inorganic and organic additions of nitrogen and fallowing have also been shown to increase levels of soil-emitted N 2 O. The objectives for this study were: (i) to confirm that losses of N 2 O are higher under ZT than under IT in Alberta Parkland agroecosystems; (ii) to compare the relative influence of urea fertilizer (56 or 100 kg N ha -1 ), field pea residue (dry matter at 5 Mg ha -1 ), sheep manure (dry matter at 40 Mg ha -1 ) additions, and fallow on total N 2 O losses; and (iii) to investigate possible interactions between fertility and tillage treatments. Gas samples were collected using vented soil covers at three sites near Edmonton, Alberta during 1993, 1994, and 1995. Gas samples were analyzed using a gas chromatograph equipped with a 63 Ni electron capture detector. Estimated annual N 2 O loss ranged from 0.1 to 4.0 kg N ha -1 . Emissions during summer were slightly higher, similar, or lower on ZT compared to those under IT, but were consistently lower on ZT plots during spring thaw. Combined estimates (spring plus summer) of N 2 O loss under ZT were equal to or lower than those under IT. Highest overall losses were observed on fallow plots, followed by fertilizer, pea residue, and then either manure or control plots. We conclude that ZT management systems have potential for reducing agricultural greenhouse gas emissions in the Alberta Parkland region. Les émissions durant l'été étaient légèrement supérieures, semblables ou inférieures en semis direct qu'en travail classique, mais au dégel du printemps elles étaient régulièrement moins fortes en SD. Les valeurs combinées (printemps et été) des déperditions en SD étaient, soit semblables soit inférieures à celles obtenues en régime TI. C'est la jachère qui entraînait les déperditions totales les plus fortes, suivie de la fumure minérale, des restes de culture de pois et de, soit l'apport de fumier de mouton ou le traitement témoin. Il ressort de ces observations que le semis direct peut réellement permettre de réduire les émissions de gaz agricoles à effet de serre en Alberta dans la région de la tremblaie boréale.

Previous field research in Alberta has suggested that denitrification occurs mostly when soil thaws in the spring, with associated soil water saturation. Our objective was to determine if denitrification and N2O emission in fact take place in cold, thawing soil in the field. Denitrification and N2O flux were measured in two springs and the intervening summer. Cylinders were placed in soil in November, 1988, and 57 kg N ha−1 of 15Nlabeled KNO3 was added. Soil 15N mass balance technique showed 23 kg N ha−1 of added-N was lost by 15 May 1989. Gas trappings were made (28 March to 29 April) and nearly all of the N2O emission (3.5 kg N2O-N ha−1) occurred during an 11-d period of thaw. The accumulated N2O flux from 20 June to 31 August was small (0.5 kg N2O-N ha−1, or less); during that time there were no rainfall events intense enough to produce water saturated soil. In 1990, 15N-labeled KNO3 (100 kg N ha−1) was applied on 26 March (outset of the thaw) and mass balance showed 32.7 kg N ha−1of added-N was lost by 7 May. A flux of 16.3 kg N2O-N ha−1 occurred largely in a 10-d period during and immediately after soil thaw. The N2O emitted from soil left a considerable fraction of the lost N unaccounted for. This unaccounted N was most likely lost as gaseous N other than N2O (e.g., N2). We conclude that large amounts of soil nitrate may be denitrified, with smaller amounts emitted as N2O, as the soil thaws and soon thereafter. Key words: Denitrification, frozen soil, thawing soil, nitrogen, nitrous oxide

Composting municipal solid waste and biosolids and applying it on arable land have become an alternative way to treat waste in large municipalities in North America. However, cost of compost transportation and application constrains the compost use on the land further away from where it is produced. A fouryear experiment was conducted (1998)(1999)(2000)(2001) in less productive soils in Alberta to determine the effect of once in four year application of cocompost on soil nutrient dynamics and crop N uptakes. There were three crop blocks: barley (Hordeum vulgare L.), wheat (Triticum aestivum L), and canola (Brassica rapa), and they were rotated annually. The compost was only applied in 1998 at a rate of 50, 100 and 200 t/ha. Soil samples were taken in spring of every year after initial compost application to determine extractable N, P, K, S, Cu, Zn, Soil pH and EC. Each year, crops were harvested and N uptake was determined. Total concentrations of an array of heavy metals in the first year and fourth year after compost application were determined as well. The results showed that the release of N from the compost was high in the first year after compost application and then declined in each subsequent year. Similar to that release pattern was sulphur. The release of phosphorus from compost was steady throughout the four-year experimental time. Crop N uptake from compost application varied with crops and sites. The over all N use efficiency for three crops and two sites was 11%, 3%, 1% and 2% for the first and subsequent three years. The total heavy metal concentrations in the compost amended soils in the first and fourth year after compost application were similar, and they were below the standard of Canadian Fertilizer Act. Our results showed that N released from compost occurred mostly in the first two years after application, suggesting that an application frequency of once in every second year may be better than the once in every four year application strategy, especially with 100 t/ha application rate.

2001. Response of pea to rhizobia inoculation and starter nitrogen in Alberta. Can. J. Plant Sci. 81: 637-643. The introduction of new semileafless cultivars has contributed to the rapid expansion of pea (Pisum sativum) on the Canadian prairies. To determine the response of four new semi-leafless cultivars to rhizobia inoculation and starter fertilizer N, 58 field trials were conducted from 1995 to 1998 over a wide geographic region of Alberta. However, due to possible cross-contamination in 1995 and 1996 between inoculated and uninoculated treatments, average inoculation responses were only determined for the 22 trials conducted in 1997 and 1998. Rhizobia inoculation increased seed yield in 9 of the 22 trials by an average of 14%. The frequency of an inoculation benefit was only slightly higher (45% vs. 38%) on land with no history of legumes (n = 11) than on land that had grown a legume crop (n = 8), but the magnitude of the inoculation benefit was appreciably greater (19 vs. 5%) on land with no history of legumes. A significant interaction of inoculation with pea cultivar was observed in 6 of 22 trials: Majoret pea was the most responsive cultivar to inoculation while Baroness pea was the least responsive. Application of N fertilizer (20, 40 or 60 kg N ha -1 ) increased pea yield in 24% of the 58 trials conducted by an average of 9%. When spring soil NO 3 -N to 30 cm was less than 20 kg N ha -1 , application of N fertilizer increased pea yield in 33% of the trials by an average of 11% (n = 12). The modest benefits of rhizobia inoculation or starter N fertilizer in most trials, despite appreciable deficits between spring soil NO 3 -N and accumulation of N by pea, was likely due to adequate nodulation of pea by indigenous rhizobia. . L'introduction de nouveaux cultivars semi-aphylles a concouru à une expansion rapide de la culture du pois de plein champ (Pisum sativum) dans les Prairies canadiennes. De 1995 à 1998, les auteurs ont procédé à 58 essais sur le terrain, un peu partout en Alberta, pour vérifier la réaction de quatre nouvelles variétés de ce genre à l'inoculation de rhizobium et à un engrais de démarrage azoté. Malheureusement, une contamination croisée possible entre les plants inoculés et ceux qui ne l'étaient pas en 1995 et en 1996 n'a permis d'établir la réaction moyenne des variétés à l'inoculation que pour les 22 essais effectués en 1997 et en 1998. L'inoculation de rhizobium a augmenté le rendement grainier d'en moyenne 14 % dans 9 essais sur 22. L'amélioration attribuable au traitement est légèrement plus élevée (45 % contre 38 %) sur les terrains n'ayant jamais servi à la culture de légumineuses (n = 11) que sur ceux déjà utilisés à cette fin (n = 8), mais l'inoculation est notablement plus efficace (19 % contre 5 %) sur les sols sans antécédents de culture de légumineuse. On remarque une interaction significative entre l'inoculation et le cultivar dans 6 essais sur 22. Ainsi, la variété Majoret réagit le mieux à l'inoculation tandis que le cultivar Baroness y est le plus réfractaire. L'app...

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