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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.

Annual crop production in the Canadian prairies is undergoing significant change. Traditional monoculture cereal cropping systems, which rely on frequent summer‐fallowing and use of mechanical tillage, are being replaced by extended and diversified crop rotations together with the use of conservation tillage (minimum and zero‐tillage) practices. This paper reviews the findings of western Canadian empirical studies that have examined the economic forces behind these land use and soil tillage changes. The evidence suggests that including oilseed and pulse crops in the rotation with cereal grains contributes to higher and more stable net farm income in most soil–climatic regions, despite a requirement for increased expenditures on purchased inputs. In the very dry Brown soil zone and drier regions of the Dark Brown soil zone where the production risk with stubble cropping is high, the elimination of summer fallow from the cropping system may not be economically feasible under present and near‐future economic conditions. The use of conservation tillage practices in the management of mixed cropping systems is highly profitable in the more moist Black and Gray soil zones (compared with conventional mechanical tillage methods) because of significant yield advantages and substantial resource savings that can be obtained by substituting herbicides for the large amount of tillage that is normally used. However, in the Brown soil zone and parts of the Dark Brown soil zone, the short‐term economic benefits of using conservation tillage practices are more marginal and often less profitable than comparable conventional tillage practices.

those methods as they have been used from the Canadian Prairie Provinces to the southern Great Plains of Successful dryland crop production in the semiarid Great Plains the United States and the resultant effects on system of North America must make efficient use of precipitation that is often limited and erratic in spatial and temporal distribution. The purpose WUE. Additionally, differences in precipitation use effiof this paper is to review research on water use efficiency and precipita-ciency (PUE) between cropping systems across the Great tion use efficiency (PUE) as affected by cropping system and manage-Plains region are identified. ment in the Great Plains. Water use efficiency and PUE increase with residue management practices that increase precipitation storage METHODS FOR INCREASING PSE, efficiency, soil surface alterations that reduce runoff, cropping se-WUE, AND PUE quences that minimize fallow periods, and use of appropriate management practices for the selected crop. Precipitation use efficiency on Tillage Effects on PSE a mass-produced basis is highest for systems producing forage (14.5 kg ha Ϫ1 mm Ϫ1 ) and lowest for rotations with a high frequency of oilseed Precipitation storage efficiency increases as tillage incrops (4.2 kg ha Ϫ1 mm Ϫ1 ) or continuous small-grain production in the tensity is reduced during the summer fallow period. The southern plains (2.8 kg ha Ϫ1 mm Ϫ1 ). Precipitation use efficiency when increased soil water storage is a result of both maintaincalculated on a price-received basis ranges from $1.20 ha Ϫ1 mm Ϫ1 (for ing crop residues on the soil surface and reducing the an opportunity-cropped system with 4 of 5 yr in forage production number of times that moist soil is brought to the surface in the southern plains) to $0.30 ha Ϫ1 mm Ϫ1 {for a wheat (Triticum as tillage intensity is reduced. Data from winter wheataestivum L.)-grain sorghum [Sorghum bicolor (L.) Moench]-fallow fallow systems at North Platte, NE (Smika and Wicks, system in the southern plains}. Throughout the Great Plains region, 1968), and Sidney, MT (Tanaka and Aase, 1987), show PUE decreases with more southern latitudes for rotations of similar fallow PSE increasing from under 25% to around 40% makeup of cereals, pulses, oilseeds, and forages. Forage systems inas tillage intensity decreased from moldboard plow to the southern Great Plains appear to be highly efficient when PUE is computed on a price-received basis. In general across the Great no-till (Fig. 1, top). Data collected at Bushland, TX, fol-Plains, increasing intensity of cropping increases PUE on both a mass-lowed a similar trend with PSE increasing from 15% with produced basis and on a price-received basis.

oilseed crop produced in the USA, canola is the dominant oil crop in Canada. The cool climatic conditions Oilseed crops are grown throughout the semiarid region of the characteristic of the Canadian prairies provide an ideal northern Great Plains of North America for use as vegetable and industrial oils, spices, and birdfeed. In a region dominated by winter environment for Brassica spp. oilseeds and flax (Table and spring wheat (Triticum aestivum L. emend. Thell.), the accep-2) while the climate found in the USA is better suited tance and production of another crop requires that it both has an to the warm season crops like soybean and sunflower. agronomic benefit to the cropping system and improve the farmers' In the northern Great Plains, soybean is a relatively economic position. In this review, we compare the adaptation and new crop finding a place in semiarid cropping systems rotational effects of oilseed crops in the northern Great Plains. Canola with the development of early maturing, low heat-unit (Brassica sp.), mustard (B. juncea and Sinapis alba L.), and flax cultivars (Miller et al., 2002). As a result, the vast major-(Linum usitatissimum L.) are well adapted to cool, short-season conity of soybean production in both the USA and Canada ditions found on the Canadian prairies and northern Great Plains occurs in wetter regions east of the Great Plains. Howborder states of the USA. Sunflower (Helianthus annuus L.) and safflower (Carthamus tinctorius L.) are better adapted to the longer ever, for the other oilseed crops listed in Table 1, the growing season and warmer temperatures found in the northern and majority of production occurs within the northern Great central Great Plains states. Examples are presented of how agronomic Plains. practices have been used to manipulate a crop's fit into a local environ-Diversification within cereal-based cropping systems ment, as demonstrated with the early spring and dormant seeding can be critical to breaking pest infestations that are management of canola, and of the role of no-till seeding systems in common with monoculture (Bailey et al., 1992, 2000; allowing the establishment of small-seeded oilseed crops in semiarid Elliot and Lynch, 1995; Holtzer et al., 1996; Krupinsky regions. Continued evaluation of oilseed crops in rotation with cereals et al., 2002). Results of crop rotation studies in the Great will further expand our understanding of how they can be used to Plains revealed that where oilseeds are adapted, their strengthen the biological, economic, and environmental role of the region's cropping systems. Specific research needs for each oilseed

Field measurements of N2O emissions from soils are limited for cropping systems in the semiarid northern Great Plains (NGP). The objectives were to develop N2O emission-time profiles for cropping systems in the semiarid NGP, define important periods of loss, determine the impact of best management practices on N2O losses, and estimate direct N fertilizer-induced emissions (FIE). No-till (NT) wheat (Triticum Aestivum L.)-fallow, wheat-wheat, and wheat-pea (Pisum sativum), and conventional till (CT) wheat-fallow, all with three N regimes (200 and 100 kg N ha(-1) available N, unfertilized control); plus a perennial grass-alfalfa (Medicago sativa L.) system were sampled over 2 yr using vented chambers. Cumulative 2-yr N2O emissions were modest in contrast to reports from more humid regions. Greatest N2O flux activity occurred following urea-N fertilization (10-wk) and during freeze-thaw cycles. Together these periods comprised up to 84% of the 2-yr total. Nitrification was probably the dominant process responsible for N2O emissions during the post-N fertilization period, while denitrification was more important during freeze-thaw cycles. Cumulative 2-yr N2O-N losses from fertilized regimes were greater for wheat-wheat (1.31 kg N ha(-1)) than wheat-fallow (CT and NT) (0.48 kg N ha(-1)), and wheat-pea (0.71 kg N ha(-1)) due to an additional N fertilization event. Cumulative losses from unfertilized cropping systems were not different from perennial grass-alfalfa (0.28 kg N ha(-1)). Tillage did not affect N2O losses for the wheat-fallow systems. Mean FIE level was equivalent to 0.26% of applied N, and considerably below the Intergovernmental Panel on Climate Change mean default value (1.25%).

Previously published data were used to examine the N economy of pulse crops typically grown on the Northern Great Plains with the goal of assessing the potential contribution of field pea (Pisum sativum L.), lentil (Lens culinaris Medik.), chickpea (Cicer arietinum L.), common bean (Phaseolus vulgaris L.), and faba bean (Vicia faba L.) to soil N accretion. Incremental changes in soil N associated with the pulse crops (i.e., the nitrogen increment, Ninc), were strongly correlated to N 2 fixation and were highly variable. Data suggest that crops that can achieve relatively high levels of N 2 fixation, such as faba bean, field pea, and lentil are more likely to contribute positively to the overall N economy, particularly when a cropping system is evaluated over a long term. In contrast, pulse crops that typically achieve only modest levels of N 2 fixation such as desi and kabuli chickpea and common bean are more likely to be either N neutral or contribute to a soil N deficit. Because of extreme variability in levels of N 2 fixation achieved, presumably reflecting variability in soil productivity as well as variations in local climate and weather, the Ninc of pulse crops likewise is highly variable. Thus, the N contribution to a subsequent crop is difficult to predict with any certainty, particularly on a yearly or short-term basis.

Typic Borolls) soil zones of the Canadian prairies (Gan and Noble, 2000). The area planted to lentil in Saskatch-Crops grown in previous years impact the amounts of residual soil ewan increased from 300 000 ha in 1995 to 670 000 ha water and nutrients available for subsequent plant growth. Appropriate sequences allow efficient use of the available soil resources by in (Anonymous, 2001. The inclusion of these crops the crop to increase yields at a system's level. This study was conducted as alternatives to cereals allows producers to become to determine whether the grain yield and grain crude protein concenless reliant on summer fallow and monoculture cropping tration (GCPC) of durum wheat (Triticum turgidum L.) were related systems. Expanded production of these alternative crops to crops grown in the previous 2 yr. Durum was grown following provides producers the opportunity to grow cereal crops pulses [chickpea (Cicer arietinum L.), lentil (Lens culinaris Medik.), on different types of stubble. The rotational benefits and dry pea (Pisum sativum L.)], oilseed [mustard (Brassica juncea derived from these opportunities are not well docu-L.) or canola (B. napus L.)], and spring wheat (Triticum aestivum L.) in southwest Saskatchewan from 1996 to 2000. Durum increased mented in this region. grain yields by 7% and GCPC by 11% when grown after pulse cropsTypes of crops grown in previous years may impact rather than after spring wheat. Durum after oilseeds increased grain the soils differently, affecting the amounts of residual yield by 5% and GCPC by 6%. Pulse and oilseed crops grown for soil water and nutrients available for subsequent plant the previous 2 yr increased durum grain yield 15% and GCPC 18% growth. Arranging crops in an appropriate sequence compared with continuous wheat systems. Fall residual soil NO 3 -N allows them to use the available resources more effiand available soil water accounted for 3 to 28% of the increased durum ciently and improves soil productivity at a system's level. yield in two of five site-years, whereas those two factors accounted for Zentner et al. (2001) reported that spring wheat GCPC 12 to 24% of the increased GCPC in three of five site-years. Durum grain yield was negatively related to GCPC. The relationship was