2006 Annual Report
Dickinson Research Extension Center
1089 State Avenue
Dickinson, ND 58601
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Patrick M. Carr
and seed crops cannot be grown profitably in the prairie region of
wheat was planted on over 0.4 million ha (1.1 million acres) in southwestern
Barley (Hordeum vulgare L.), oat (Avena sativa L.), and corn (Zea mays L.) were the second, third, and fourth most widely grown grain crops (after wheat) during 2004 in southwestern North Dakota, respectively. However, Swenson and Haugen (2005) project -$15 ha-1 (-$6 acre-1) generated for malt barley production in 2006, -$84 ha-1 (-$34 acre-1) for oat, and -$67 ha-1 (-$27 acre-1) for grain corn. Swenson and Haugen (2005) also project negative returns for several seed crops in the region in 2006, including sunflower (Helianthus annuus L.; -$12 ha-1 [-$5 acre-1]); canola (Brassica napus L. and B. rapa L.; -$62 ha-1[-$25 acre-1]), flax (Linum usitatissinum L.; -$30 ha-1 [-$12 acre-1]), and field pea (Pisum sativum L. subsp. sativum; -$32 ha-1 [-$13 acre-1]).
Not all seed crops are expected to generate negative returns in the region if grown in 2006. For example, chickpea (Cicer arietinum L.) is expected to return $57 ha-1 ($23 acre-1), lentil (Lens culinaris Medik.) is expected to return $44 ha-1 [$18 acre-1]), and mustard (Brassica spp.) is expected to return $35 ha-1 ($14 acre-1). However, disease control continues to be a significant problem in chickpea, mustard production is constrained by a small market with limited growth potential, and lentil production has not been profitable consistently. For example, lentil returned an average of -$80 ha-1 (-$32 acre-1) when grown within the region in 2002 (FinBin, 2005).
Alfalfa (Medicago sativa L.) was grown on over 80,000 ha (200,000
acres) in southwestern
Rotational Benefits of Forages
Impact on Yield
research studies suggest that grain and seed yield increases result in
subsequent crops when forages are inserted into crop rotations. Entz et al. (2002) summarized results of research in
Much of the rotation yield benefit to grain and seed crops following alfalfa is attributed to the biological N2-fixing ability of the legume species. Fertilizer replacement values in excess of 100 kg ha-1 (90 lb acre-1) are possible for alfalfa and some other legume forages even after removing a hay crop, if regrowth is plowed under (Entz et al, 2002). The impact of alfalfa and other legumes on the soil N pool may even be greater when these forage species are grazed and not hayed, since there is considerable recycling of nutrients.
There are some rotational yield benefits provided by alfalfa and other forages that result from non-N factors. Many of these non-N benefits are attributed to improvements in soil quality. For example, larger and more stable aggregates occurred in soils where perennial forages were grown compared with grain crops in several studies summarized in the review paper by Entz et al. (2002). Other research discussed by these same authors indicated that soil microbial activity also was greater in soils where perennial forages were grown, even in semiarid regions.
Reports of weed suppression provided by forages are widespread in the scientific literature. In their review paper, Entz et al. (2002) cited several studies where weed production was significantly less in rotations that included forage crops compared with those which did not. In one study, wild oat (Avena fatua L.) dockage was <1% of the grain produced in forage-containing rotations compared with 15% in continuous wheat or wheat-fallow systems.
identifying weed suppression resulting after incorporating forages into
rotations with grain crops is supported by on-farm observations. Over 80% of commercial grain and forage
producers surveyed in
The impact of forages on reducing pests is not limited to weeds. For example, common root rot (Helminthosporium and Fusarium spp.) infection in wheat was suppressed when red clover (Trifolium pretense L.) was grown between two wheat crops in a red clover-spring wheat-canola-spring wheat rotation compared with a continuous wheat monoculture (Clayton et al., 1997). Likewise, common root rot was suppressed only when a 3-yr hay crop was included among several rotations in a separate study described by Entz et al. (2002).
economic studies have compared the impact of forages on crop rotation
profitability. Zentner et al. (1986) did compare the
economic returns generated by forage-based cropping systems to rotations that
consisted only of grain and seed crops. The forage-based cropping systems had
lower production costs and more stable net returns than the continuous grain
production systems. The greater income stability associated with the
forage-based cropping systems lowered the risk associated with field crop
production in the northern
Shortcomings of Perennial Forages
Drought-Induced Yield Suppression
benefits do not always result when alfalfa and other perennial forages are
inserted into rotations with grain and seed crops. Rather, yield reductions
oftentimes occur in semiarid regions in the northern
of studies indicating that grain and seed yields are depressed following
perennial forages is not unexpected in semiarid regions. Soil water reserves oftentimes are depleted
following perennial forages and must be at least partially replenished to avoid
drought-induced yield depression in subsequent grain or seed crops. A study cited by Entz
et al. (2002) in western
benefits provided by diverse rotations in suppressing pests in the northern
Great Plains have been summarized in papers written by scientists both in
Many perennial forage stands are maintained for
several years after first being established, even though research indicates
that most of the benefits provided to subsequent grain and seed crops occur
within the first few years following establishment. For example, Entz
et al. (1995) summarized results of several studies indicating that optimum N
accumulation and weed suppression occurs within three years of alfalfa stand
establishment. However, these
researchers reported that the average stand duration for alfalfa was 8 years in
semiarid portions of the northern
Extent and Potential of Annual Forages
forages are an important contributor to the feed supply in the northern
crops can be grown alone or in mixtures for forage. While forage yield may not
increase (Baron et al., 1992), seasonal distribution often improves when
cereals mixtures are grown. Research cited by Entz et
al. (2002) demonstrated that mixtures of spring and winter cereals provide
earlier grazing than winter cereals alone, but later grazing than spring
cereals alone. Unpublished data collected at
of barley or oat and field pea are grown in the northern
Perennial pastures generally are believed to be the least expensive feed sources for beef cattle (Entz et al., 2002). However, annual forages can be used to extend the grazing season when perennial species cannot or should not be grazed. A common practice is to pasture animals on crop residue and regrowth following grain and seed harvest during fall and winter months. Alternatively, annual crop mixtures can be used to extend the grazing system, as has already been mentioned. Finally, cereals can be swathed and then grazed by cattle during winter months. All these strategies can reduce beef cattle production costs by lowering or even eliminating the need to overwinter cattle in confinement systems.
Rotational Benefit of Annual Crops
Substituting annual for perennial forages solves some of the problems that exist when perennial species are inserted into rotations with grain and seed crops. Annual forages have a shallower root system and generally extract less water than long-lived perennial species like alfalfa. As a result, drought-induced yield depression in subsequent grain and seed crops is less likely following annual forages because soil water recharge can occur. Soil water content may even be greater following annual forages than grain and seed crops since forage generally is harvested earlier. As a result, a wider window exists for soil water reserves to be recharged before the next crop is grown.
Annual forages provide flexibility for changing crops in diverse rotations that is not available when long-lived perennial species are grown. The biological diversity that may result from rotating annual grain, seed, and forage crops can be used to control pests. Cereals and certain dicotyledonous plant species also give producers the choice of harvesting the crop for forage or for grain, depending on economic, environmental, and other factors.
Weed suppression can occur when annual forages are inserted into rotations with grain and seed crops, even though the weed control benefits offered by perennial forages may be greater. Wild oat populations were significantly lower following triticale that was hayed compared with spring wheat that was harvested for grain (Schoofs and Entz, 2000). Fewer wild oat plants occurred following the triticale forage crop even when a grass herbicide (tralkoxydim) was applied in the wheat grain crop to control wild oat. Annual forages have reduced weed populations in other studies cited by these two researchers.
The N benefits of forage legumes are not restricted to alfalfa and other perennial species. Annual legumes including various medic (Medicago spp.) and clover species have been used successfully for decades to supply part if not all of the N needs for subsequent wheat crops (Puckridge and French, 1983). Grain yield increases of up to 50% along with increases in grain protein of 1% to 2% for wheat resulted from substituting fallow with annual legume pasture in that country. The enhancements in grain yield and quality are attributed largely to the biological N2-fixing ability of the annual legume species.
Challenges Faced When Incorporating Annual Forages into Rotations
Obstacles exist which inhibit the widespread incorporation of annual forages into rotations with grain and seed crops. A trend has existed for decades in agriculture to specialize, so many farms that formerly contained both crop and livestock enterprises have maintained one and eliminated the other. As a result, much of the familiarity and knowledge regarding forage crop production no longer exist on many farms where grain and seed crops presently are grown.
Much of the infrastructure that once supported integrated crop-livestock enterprises has been dismantled. Krall and Schuman (1996) pointed out that watering systems and fences would need to be improved or installed if forages were grown and grazed on many farms where grain and seed crops presently are grown. Haying rather than grazing an option, but nearby markets for locally grown hay may not exist.
Work is underway to develop cropping systems where
legume forages are rotated with grain and seed crops to reduce reliance on N fertilizer
and pesticide inputs while, at the same time, maintain or enhance grain crop
yield. This effort, patterned after an Australian farming method described in
detail by Puckridge and French (1983), presently is
This review paper has briefly identified some of the advantages provided by forages if incorporated into rotations with grain and seed crops. A much more thorough evaluation of the benefits offered by forages if incorporated into crop rotations is provided by Entz et al. (2002). An additional paper by some of the same authors which describes the benefits of integrated crop-livestock systems in semiarid and subhumid regions should be published in Agronomy Journal in 2006 or 2007.
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