Martin H. Entz

Potential of forages to diversify cropping systems in the Northern Great Plains

cated to cultivated forage crop production in the three Canadian prairie provinces (Manitoba, Saskatchewan, Cultivated forage crops are grown on almost 12 million ha on the and Alberta) and three U.S. states (North Dakota, northern Great Plains. This paper reviews the benefits of diversifying annual crop rotations with forage crops and highlights innovations in South Dakota, and Montana) totals 7.8 million ha of forage systems. Agronomic benefits of rotating forage crops with cultivated hay and 3.8 million ha of cultivated pasture annual grain crops include higher grain crop yields following forages (Alberta Agric., Food, and Rural Dev., 1999; Manitoba (up to 13 yr in one study), shifts in the weed population away from Agric. and Food, 1999; Saskatchewan Agric. and Food, arable crop weeds, and improved soil quality. Perennial legumes in 1999; NASS, 1999). Many farmers and ranchers use culrotation also reduce energy requirements by adding significant tivated forages to complement the approximate 44 milamounts of N to the soil. Soil water availability may limit the extent lion ha (Alberta Agric., Food, and Rural Dev., 1999; to which forages benefit following crops. Under semiarid conditions, Manitoba Agric. and Food, 1999; Saskatchewan Agric. forages can actually reduce yields of the following crops, and as such, and Food, 1999; NASS, 1999) of native rangeland in tillage practices that conserve soil water have been developed to this region. partially address this problem. Forages in rotation provide environmental benefits, such as C sequestration, critical habitat for wildlife, Forage is produced and conserved during the short and reduced NO3 leaching. A wider range of annual plant species are growing season and fed during the remainder of the now used in forage systems in an effort to extend the grazing season year. Hay is the predominant winter feed, followed by and to maximize use of water resources. Intensive pasture managestraw, silage, stockpiled perennial pasture, and swathed ment using cultivated forages is on the increase as is the use of alfalfa annual pastures (Small and McCaughey, 1999). The win(Medicago sativa L.) in grazing systems; in some cases, bloat-reduced ter feeding period for beef cattle (Bos taurus) in western alfalfa cultivars are used. Pasture-based systems appear to provide Canada is widely reported to exceed 200 d per year benefits for both animal and human health and arguably the health (Mathison, 1993). However, this varies by region and of the environment. Pasture systems are less nutrient exhausting than year, mainly depending on period of snow cover. In hay systems. As a result, nutrient management strategies will differ Alberta during 1999, the mixed grassland region, most in the following crop. Additional research is required to optimize the role of cultivated pastures in grain-based cropping systems. representative of the NGP area, had an average 155 winter feeding days compared with 201 in the boreal transition zone, which lies to the north of the prairie (Anonymous, 2000). Approximately 10% of forage proF production in the northern Great Plains duction is used for dairy cows located in the NGP region. (NGP) of the USA and Canada involves cultivated Some forage is also exported outside North America and native pasture and hay production. The area dedi[e.g., dehydrated alfalfa cubes and pellets and compacted timothy (Phleum pratense L.) hay]. Very little M.H. Entz, Dep. of Plant Sci., Univ. of Manitoba, Winnipeg, MB, Canada R3T 2N2; V.S. Baron, Agric. and Agri-Food Can., Lacombe forage is typcially imported into this region although reRes. Cent., Lacombe, AB, Canada T4L 1W1; P.M. Carr, North Dakota distribution of forage does occur when localized droughts State Univ., Dickinson Res. and Ext. Cent., 1089 State Ave., Dickinreduce forage supply. son, ND 58601; D.W. Meyer, Dep. of Plant Sci., North Dakota State Alfalfa is the main forage legume and is grown on Univ., Fargo, ND 58105; S.R. Smith, Jr., Dep. of Crop, Soil, and 61% of cultivated forage hayland in the U.S. NGP. AlEnviron. Sci., 424 Smyth Hall, Virginia Tech, Blacksburg, VA 240610404; and W.P. McCaughey, Agric. and Agri-Food Can., Brandon falfa’s role in grazing systems is increasing (Smith and Res. Cent., Brandon, MB, Canada R7A 5Y3. Received 22 Jan. 2001. *Corresponding author (m_entz@umanitoba.ca). Abbreviations: CLA, conjugated linoleic acid; DM, dry matter; NGP, northern Great Plains. Published in Agron. J. 94:240–250 (2002). ENTZ ET AL.: DIVERSIFYING CROPPING SYSTEMS WITH FORAGES IN THE NORTHERN GREAT PLAINS 241 Singh, 2000). Other forage legumes are also grown 50% higher from land previously cropped to alfalfa for 3 yr than from land previously cropped to nonlegumes where alfalfa is not adapted [e.g., red clover (Trifolium pratense L.) and alsike clover (T. hybridium L.) in wetter such as corn (Zea mays L.), wheat, or flax (Linum usitatissimum L.). Similar results continue to be reported from and acid soil zones, sainfoin (Onobrychis viciafolia L.) in dryland pastures, or where a nonbloating legume is studies at Melfort, SK (Campbell et al., 1990); Winnipeg, MB (Poyser et al., 1957); and Lethbridge, AB (Ellert, desired]. There is significant potential to utilize these better adapted, alternative perennial forage legumes in 1995) as well as from two ongoing classical long-term studies of crop rotation in western Canada: The Univerthe region though grower education is required. Many different grass species are used in cultivated forage syssity of Alberta’s Breton Plots (initiated in 1930) (Ellert, 1995) and Agriculture and Agri-Food Canada’s longtems, ranging from the droughtand salt-tolerant wheatgrasses (Agropyron spp.) to flooding-tolerant reed caterm study at Indian Head, SK (initiated in 1958) (Campbell et al., 1990). narygrasses (Phalaris spp.). Many annual C3 and C4 plant species are used to fill gaps in the feed supply (Kilcher In a survey of Manitoba and Saskatchewan forage producers, 71% of respondents indicated higher grain and Heinrichs, 1961; Baron et al., 1992; Carr et al., 1998). Forage is defined as, “any plant whose vegetation is yields after forages than in annual crop rotations (Entz et al., 1995). Rotational yield benefits were greatest in eaten by livestock” (Heath et al., 1973), and as such, many different plants are used, including crop residues eastern and northern zones and lowest in drier, western and southern zones. In one of the best studies ever (e.g., corn stalks and chaff) and hay harvested for remnant areas and roadside ditches. These forage sources published on the long-term residual yield benefits of including forage in a cropping system (McLennan, AB), are especially important in drought years such as 2000 in Montana. Forage seed production is also an important Hoyt (1990) reported that for the first 8 yr after forage termination, wheat yields were 66 to 114% greater after industry in the region though it occupies a relatively small area compared with forage production. forage relative to continuous wheat. Yield differences started to decline after 8 yr although wheat yields in The percent of arable cropland that is rotated with forage ranges from 5 to 15% in the region. Two recent the alfalfa systems were still higher (P 0.05) than the control in the 10th and 13th year after sward breaking. surveys have characterized forage and beef production in western Canada (Entz et al., 1995; Small and McIn areas of the NGP where water seriously limits crop productivity, inclusion of perennial forages can reduce Caughey, 1999). Objectives of this paper are to (i) review agronomic, crop yield in following crops due to forage-induced drought. Working in west-central Saskatchewan, Brandt economic, and environmental benefits and risks of diversifying cropping systems with forage crops; (ii) idenand Keys (1982) determined that available soil water in spring was lower after a 2-yr alfalfa crop than in a tify means to enhance the positive attributes of forages in NGP cropping systems and to make forages a more continuous grain rotation. A full year of fallow was insufficient to fully replenish the soil profile with water important component of the cropping system; and (iii) highlight research challenges for the future. in the alfalfa system relative to the grain system. In central Saskatchewan, Austenson et al. (1970) reported that alfalfa in rotation depressed wheat yield in the first ROTATIONAL BENEFITS OF FORAGES crop after breaking even after a full year of summer IN THE NORTHERN GREAT PLAINS fallow. Interestingly, they observed that alfalfa with CROPPING SYSTEMS bromegrass (Bromus inermis Leyss.) or bromegrass Forage benefits have received less attention in the alone did not affect wheat yields significantly. Others NGP than elsewhere, such as the humid U.S. Midwest (e.g., C.A. Campbell, personal communication, 2000) where alfalfa has traditionally been rotated with grain have suggested that low cereal yields after alfalfa could crops or areas of Australia where unique, self-regeneratbe due to allelopathic effects from alfalfa, and such ing forage species are grown in grain-based cropping effects are greatest under dry soil conditions. However, systems (Grace et al., 1995). The short growing season no studies have been conducted to substantiate this sugand relatively dry conditions (i.e., low precipitation and gestion. high evaporative demand for water) in the NGP will In wetter areas of the NGP, these water-depleting modify rotational benefits of forages relative to wetcharacteristics of alfalfa and other perennial forages are ter areas. often viewed as desirable. For example, dewatering Some of the best information on forage rotational characteristics of perennial forages play an important benefits in the NGP has come from long-term crop role in soil salinity management. Soil salinization is a rotation studies, many of which were established soon threat to the long-term sustainability of cro

Crop yield and soil nutrient status on 14 organic farms in the eastern portion of the northern Great Plains

Cropping records from 13 organic farms in the eastern Canadian prairies and one in North Dakota (1991 to 1996) were surveyed to determine crop rotation pattern, yields and soil nutrient status. Major crops included cereal grains, forages, and green manure legumes. Organic grain and forage yields averaged from one-half to almost double conventional yields. Soil N, K and S levels on organic farms were generally sufficient; however, levels of available soil P were deficient in several instances. Key words: Crop rotation, weeds, forages, green manure crops

Energy use and efficiency in two Canadian organic and conventional crop production systems

A goal in sustainable agriculture is to use fossil fuel energy more efficiently in crop production. This 12-year study investigated effects of two crop rotations and two crop production systems (organic versus conventional management) on energy use, energy output and energy-use efficiency. The grain-based rotation included wheat ( Triticum aestivum L.)–pea ( Pisum sativum L.)–wheat–flax ( Linum usitatissimum L.), while the integrated rotation included wheat–alfalfa ( Medicago sativa L.)–alfalfa–flax. Energy use was 50% lower with organic than with conventional management, and approximately 40% lower with integrated than with the grain-based rotation. Energy use across all treatments averaged 3420 MJ ha −1 yr −1 . Energy output (grain and alfalfa herbage only) across treatments averaged 49,947 MJ ha −1 yr −1 and was affected independently by production system and crop rotation. Energy output in the integrated rotation was three times that of the grain-based rotation; however, this difference was largely due to differences in crop type (whole plant alfalfa compared with grain seed). Energy output was 30% lower with organic than with conventional management. Energy efficiency (output energy/input energy) averaged to 17.4 and was highest in the organic and integrated rotations. A significant rotation by production system interaction ( P

Pyrosequencing Reveals the Influence of Organic and Conventional Farming Systems on Bacterial Communities

It has been debated how different farming systems influence the composition of soil bacterial communities, which are crucial for maintaining soil health. In this research, we applied high-throughput pyrosequencing of V1 to V3 regions of bacterial 16S rRNA genes to gain further insight into how organic and conventional farming systems and crop rotation influence bulk soil bacterial communities. A 2×2 factorial experiment consisted of two agriculture management systems (organic versus conventional) and two crop rotations (flax-oat-fababean-wheat versus flax-alfalfa-alfalfa-wheat) was conducted at the Glenlea Long-Term Crop Rotation and Management Station, which is Canada’s oldest organic-conventional management study field. Results revealed that there is a significant difference in the composition of bacterial genera between organic and conventional management systems but crop rotation was not a discriminator factor. Organic farming was associated with higher relative abundance of Proteobacteria, while Actinobacteria and Chloroflexi were more abundant in conventional farming. The dominant genera including Blastococcus, Microlunatus, Pseudonocardia, Solirubrobacter, Brevundimonas, Pseudomonas, and Stenotrophomonas exhibited significant variation between the organic and conventional farming systems. The relative abundance of bacterial communities at the phylum and class level was correlated to soil pH rather than other edaphic properties. In addition, it was found that Proteobacteria and Actinobacteria were more sensitive to pH variation.

The nitrogen dynamics of 1-, 2- and 3-year stands of alfalfa in a cropping system

Abstract Alfalfa ( Medicago sativa L.) has long been recognized as a source of N for the subsequent crops in a rotation. However, the relationship between symbiotically fixed N and soil mineral N sources, and the way they are partitioned into harvested hay or incorporated biomass, is not well understood. Calculating N budgets (i.e. estimating N input and output in a system) is useful for increasing our understanding of N dynamics in agro-ecosystems. Field experiments were initiated to develop a basic N budget for 1–3-year-old stands of alfalfa in a crop rotation. Changes in total soil N were monitored and N 2 fixation was measured using the 15 N isotope dilution technique. The total seasonal amount of N 2 fixed generally increased with each additional year of alfalfa, ranging from 174 kg N ha −1 for first year alfalfa to 466 kg N ha −1 for third year alfalfa. Alfalfa was also very effective at accessing deep-leached NO − 3 (i.e. soil NO − 3 greater than 1 m below the soil surface). The net soil N balance indicated that an average of 84, 148 and 137 kg N ha −1 was added to the soil system for 1-, 2- and 3-year-old alfalfa stands. The results of the budgeting process sugges that alfalfa stands as short as 2 years have the potential of making significant benefits to soil N status.

Influence of annual forages on weed dynamics in a cropping system

Alternatives to herbicides are needed for weed control. Field studies were conducted in 1994/1995 and 1995/1996 to investigate the nature of forage crop-weed dynamics and to test the effect of single year forage crops on the density and community composition of annual weeds in a following field pea (Pisium sativum L.) test crop. Five spring-seeded forage treatments were compared with wheat (Triticum aestivum L.) grain crops (with or without herbicides for grassy and broadleaved weeds): winter triticale (Triticosecale) (simulation grazed); spring triticale (silage); spring/winter triticale intercrop (silage, then simulation grazed); alfalfa (Medicago sativa L.) (hay); sorghum-sudangrass (Sorghum bicolor [L.] Moench × Sorghum sudanese [Piper]) (hay); and a weedy fallow (silage). A fall rye (Secale cereale L.) grain crop and a sweet clover (Melilotis officinalis L.)/winter triticale double crop (hay, then simulation grazing) were included in the 1995/1996 trial. All forage systems were at least as effective ...

Chaff collection reduces seed dispersal of wild oat (Avena fatua) by a combine harvester

Abstract Combine harvesters have the potential to disperse weed seeds great distances. Reducing this dispersal may be important in an integrated weed management system. The objectives of this study were to determine the distance that wild oat seeds are dispersed by a combine harvester and the effect of chaff collection on combine harvester seed dispersal. This was measured by sampling wild oat seeds at varying distances behind a combine equipped with a removable chaff collection system after it passed through a wild oat patch. Chaff collection consistently reduced the amount and distance that wild oat seeds were dispersed. This occurred because more than 74% of the total wild oat seed that were ejected from the combine were in the chaff. Because most of the chaff falls in a row directly behind the combine, chaff collection only affected dispersal in this area. In 1996, chaff collection reduced wild oat seed dispersal past the wild oat patch to less than 10 seeds m−2 at 45 m, whereas without chaff collection, there was greater than 10 seeds m−2 up to 145 m. At distances beyond 145 m, chaff collection had no significant effect on seed dispersal. Chaff collection may be an important tool in an integrated weed management program because it may slow weed invasions and reduce the expansion of weed patches. Nomenclature: Wild oat, Avena fatua L. AVEFA.

Strategies and tactics for herbicide use reduction in field crops in canada: A review

There are many economic and health reasons for reducing pesticide use in Canada. Herbicide use on field crops is by far the most common pesticide use in Canada. This paper is a review of four topics related to herbicide use reduction on field crops in Canada: (1) broad strategies and (2) specific tactics for herbicide use reduction; (3) factors affecting adoption; and 4) research approaches for improving the implementation of herbicide use reduction. Numerous tactics exist to use herbicides more efficiently and herbicides can sometimes be replaced by non-chemical weed control methods. Many of these tactics and methods have been investigated and demonstrated for use on field crops in Canada. However, herbicide use reduction is fundamentally dependent upon preventative strategies designed to create robust cropping systems that maintain low weed densities. Diverse crop rotation forms the basis of preventative strategies as it inherently varies cropping system conditions to avoid weed adaptation. There is evi...

Avena fatua development and seed shatter as related to thermal time

Abstract Avena fatua seeds remaining on the plant at harvest and taken into the combine harvester may be dispersed over large areas. The objective of this study was to characterize the development of A. fatua in comparison to spring Triticum aestivum. As part of this objective, the rate of seed shed in A. fatua relative to development of T. aestivum was determined. Avena fatua and T. aestivum had similar phyllochron intervals within locations but differed between locations. Plant development as measured by the Zadoks plant development scale was consistent within plant species between locations. Seed shed in A. fatua was also consistent between locations. Most of the seed shed occurred within 2 wk, and the cumulative seed shed followed a sigmoidal pattern. The seed shed occurred as T. aestivum was ripening, and the percentage of seed shed appears to be related to the water content of the T. aestivum spike. Because of this relationship, the proportion of seed remaining on A. fatua at harvest could be managed by changing the timing of crop harvest. Nomenclature: Wild oat, Avena fatua L. AVEFA; spring wheat, Triticum aestivum L. ‘Katepawa’; growing degree days (GDD).

Mycorrhizal colonization of flax under long-term organic and conventional management

Arbuscular mycorrhizal fungi are of particular interest in organic agricultural systems. We studied the effects of crop rotation and crop management system (conventional vs. organic) on mycorrhizal colonization of flax roots, in the 12th year of a long-term crop rotation trial. Colonization was higher in organic treatments than conventional, possibly due to decreased P availability. There was a highly significant rotation × management system interaction, which may be explained by differences in the abundance of mycorrhizal and non-mycorrhizal weed species between the two management systems. Further research is required before stronger conclusions can be made. Key words: Crop rotation, arbuscular mycorrhizal fungi, flax, wild mustard, host-plant dynamics, organic agriculture