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Integrating alfalfa (Medicago sativa L.) with corn (Zea mays L.) for grain will increase biodiversity, reduce the negative environmental impact of corn monoculture and increase farm profitability. The objectives of this research were to evaluate forage productivity and nutritive value, along with stand establishment of alfalfa in a corn grain system in Iowa, Minnesota, and North Dakota. The experimental design was a randomized complete block with four replicates at each site. Treatments included were: sole corn (i.e., check; T1), sole alfalfa (T2), alfalfa intercropped into corn (T3), a prohexadione-treated alfalfa intercropped with corn (T4), and a spring-seeded alfalfa in the year after intercropping (T5), which was planted in plots with T1 the previous year. All sites had below normal rainfall in 2016 and 2017. Corn grain yield was significantly lower when intercropped with alfalfa (T3 and T4) compared with the check corn crop (no alfalfa, T1). Corn grain yield reduction ranged from 14.0% to 18.8% compared with the check (T1). Corn biomass yield was reduced by intercropped alfalfa (T3 and T4) by 15.9% to 25.8%. In the seeding year, alfalfa seasonal forage yield was significantly greater when corn competition was absent in all environments. The intercropped alfalfa from the previous season (T3 and T4) had almost double the forage yield than the alfalfa in the seeding year (spring-seeded alfalfa; T5). In the second production year, there were no meaningful forage yield differences (p > 0.05) across all treatments, indicating alfalfa in intercropping systems does not affect forage yield past the first production year. Prohexadione-calcium, a growth regulator, did not affect alfalfa stand density, forage yield and nutritive value. The forage nutritive value was dependent on harvest date not the alfalfa intercropping treatments. Results of our study suggest that establishing alfalfa with corn is feasible and can be a potential alternative for the upper Midwest region. However, when under drought conditions, this system might be less resilient since competition between alfalfa and corn for soil moisture will be intensified under drought or moisture-limited conditions, and this will likely depress corn grain yield. Research targeted to reintroduce perennial crops into the current dominant corn–soybean systems in the US Corn Belt is urgently needed to improve stability and resiliency of production systems.

Intercropping of silage maize (Zea mays L.) and alfalfa (Medicago sativa L.) is not a common practice because alfalfa generally reduces maize grain and biomass yield. The objective of this research was to evaluate the productivity and profitability of silage maize–alfalfa intercropping, with a goal to establish alfalfa and increase alfalfa productivity in the first year of production. The experiment was conducted in Fargo and Prosper, ND, USA, in 2014–2017. The design was a randomized complete block with four replicates and a split-plot arrangement. The main plot had two maize row-spacing treatments (RS), 61 and 76 cm, respectively. Treatments in the subplot were: (1) maize monoculture, (2) maize intercropped with alfalfa, (3) maize intercropped with alfalfa + prohexadione-calcium (PHX), and (4) spring-seeded alfalfa in the following year (simulating a maize–spring-seeded alfalfa crop sequence). Both alfalfa and maize were seeded the same day in May of 2014 at both locations. Prohexadione-calcium, a growth regulator to reduce internode length and avoid etiolation of alfalfa seedlings, did not improve alfalfa plant survival. Averaged across locations, RS did not have an effect on silage maize yield and alfalfa forage yield. Alfalfa established in intercropping with maize had almost double the forage yield in the following year compared with spring-seeded alfalfa following a crop of silage maize. Considering a two-year system, alfalfa intercropped with maize had higher net returns than a silage-maize followed by a spring-seeded alfalfa sequence. This system has the potential to get more growers to have alfalfa in the rotation skipping the typical low forage yield of alfalfa in the establishment year.

Adoption of cover crop interseeding in the northwestern Corn Belt in the USA is limited due to inadequate fall moisture for establishment, short growing season, additional costs, and need for adapted winter-hardy species. This study evaluated three cover crop treatments—no cover crop, winter rye (Secale cereale L.), and winter camelina (Camelina sativa (L.) Crantz)—which were interseeded at the R6 soybean growth stage, using two different soybean (Glycine max (L.) Merr.) maturity groups (0.5 vs. 0.9) and two row spacings (30.5 vs. 61 cm). The objective was to evaluate these treatments on cover crop biomass, soil cover, plant density, and soybean yield. Spring wheat (Triticum aestivum L.) grain yield was also measured the following year. The early-maturing soybean cultivar (0.5 maturity) resulted in increased cover crop biomass and soil cover, with winter rye outperforming winter camelina. However, the early-maturing soybean yielded 2308 kg·ha−1, significantly less compared with the later maturing cultivar (2445 kg·ha−1). Narrow row spacing had higher soybean yield, but row spacing did not affect cover crop growth. Spring wheat should not follow winter rye if rye is terminated right before seeding the wheat. However, wheat planted after winter camelina was no different than when no cover crop was interseeded in soybean. Interseeding cover crops into established soybean is possible, however, cover crop biomass accumulation and soil cover are limited.

In the North Central USA, intersowing cover crops into standing maize (Zea mays L.) is required to establish plants large enough to afford the benefits of a cover since there is limited favorable weather for cover crop growth after maize harvest. The objective of this study was to quantify the impacts of the planting method and time of planting of three cover crop species when grown with or without maize competition on their establishment. Experiments were conducted in three environments during 2018 and 2019. Experiments consisted of a factorial combination of timing of cover crop planting (V7 and R4 growth stage of maize), cover crop species (camelina (Camelina sativa (L.) Crantz), rye (Secale cereale L.), or radish (Raphanus sativus L.), method of sowing (drilled or broadcast), and maize removal. Initial cover crop populations were similar regardless of maize removal or stage of maize when sown, but intersown cover crops produced only 3% of the fall biomass, compared with treatments with maize-removed when sown at the V7 stage of maize and 14% when sown at the R4 stage. Limited light intensity (less than 20%) under the maize canopy was the main factor affecting interseeded cover crop development. Radish was more sensitive to shading than the other cover crops. Camelina and rye sown at the R4 stage of corn produced similar spring biomass as earlier-sown cover crops. Intersown cover crops had no negative effect on maize grain yield.

Low adoption to utilize cover crops interseeded into soybean (Glycine max (L.) Merr.), in the northern Plains in the USA, is due to a short growing season and a few adapted winter-hardy species. The objective was to evaluate the impact of interseeded winter camelina (Camelina sativa (L.) Crantz) and winter rye (Secale cereale L.) using different soybean relative maturities on soybean yield, canopy coverage, spring cover crop biomass, and subsequent wheat (Triticum aestivum L.) yield. Cover crops interseeded into early-maturing (0.4–0.8) soybean cultivars had more fall coverage compared with the 0.9 maturity cultivar, but the spring biomass was similar for all maturities. The soybean yield of the 0.9 cultivar was significantly higher, 2365 kg ha−1 compared with 2037 kg ha−1 for the 0.4 cultivar. Rye outperformed winter camelina and had higher fall canopy cover (15 vs. 7%), spring canopy cover (16% vs. 4%), and higher spring biomass (313 vs. 100 kg ha−1 dry matter). Spring wheat, after rye, yielded 90% of the check. It is not recommended to plant spring wheat following winter rye, but there was no negative yield effect from winter camelina. Interseeding cover crops into soybean in the northern Plains is possible but needs further research to optimize interseeding systems.

Faba bean (Vicia faba Roth) and pea (Pisum sativum L.) are grown worldwide as protein sources for food and feed and can be used as cover crops after wheat (Triticum aestivum L.). However, faba bean is underutilized in upper Midwest farming systems. This study was conducted to determine how faba bean relates to pea as a forage, cover crop, and in cycling of nutrients to maize (Zea mays L.) in the following season. Five faba bean cultivars and two pea cultivars, a forage pea and a field pea, were established after wheat harvest in North Dakota, in 2017 and 2018. Faba bean and pea cultivars averaged 1.3 Mg ha&minus, 1 of biomass, enough to support 1.5 animal unit month (AUM) ha&minus, 1 for a 450 kg cow (Bos taurus L.) with calf, at 50% harvest efficiency. Crude protein content was highest in faba bean cv. Boxer (304 g kg&minus, 1), with faba bean cv. Laura and forage pea cv. Arvika having similar content, and field pea having the least (264 g kg&minus, 1). Cover crop treatments did not affect maize in the following year, indicating no nutrient cycling from faba bean and pea to maize. Both cover crop species tested provided high protein forage, suitable for late grazing, with a more fibrous crop residue. Faba bean has potential as a cover crop in the upper Midwest while providing greater quality forage than pea.

Maize (Zea mays L.) silage is the preferred feedstock choice for biogas production. However, other feedstocks or mixed feedstocks might have lower environmental impact than silage maize. The objectives of this study included: 1) to determine if forage sorghum [Sorghum bicolor (L.) Moench] and forage sorghum-maize intercropping can be a viable option to replace maize in forage and biogas production, and 2) to assess the environmental impact of systems involving maize and forage sorghum intercropping and comparing the impact of those, with conventional monocrop rotations. Replicated experiments were conducted in Carrington, Fargo, and Prosper, ND, in 2013 and in Fargo, ND in 2014. Maize for silage and grain and two forage sorghum cultivars (Brown Mid Rib (BMR) and non-BMR) were grown in monoculture and in intercropping. Treatments were a total of twelve; four monocultures, four inter-row intercropped maize-sorghum, and four within-row intercropped maize-sorghum. Results across environments indicated non-BMR forage sorghum monocultures produced similar or higher biomass yield compared with maize monocultures and maize-forage sorghum mixed cultures (inter-row and within-row). Biogas yield and forage quality produced by forage sorghum monocultures, and mixtures containing forage sorghum were similar to that of maize. Thus, forage sorghum can replace, at least in part, silage maize as feedstock for feed or biogas. Forage sorghum and forage sorghum-maize intercropping had lower environmental impact compared with maize in all categories evaluated. In conclusion, intercropping of forage sorghum with maize is a promising alternative to maize silage for forage or as feedstock for biogas production.

Camelina [ Camelina sativa (L.) Crantz.] is an industrial oilseed crop in the Brassicaceae family with multiple uses. Currently, camelina is not used as a cover crop, but it has the potential to be used as such in maize ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] cropping systems. The objective of this study was to determine the agronomic performance of winter camelina intersown as a cover crop into standing soybean or maize prior to their harvest. Experiments were conducted in Fargo, ND in 2014, Prosper, ND, in 2015, and in Morris, MN in 2014 and 2015. The experimental design was a randomized complete block design with a split-plot arrangement with three replicates. The main plot was row spacing (61 and 76 cm in maize, 31 and 61 cm in soybean) while the sub-plot was maize or soybean growth stage at relay-sowing of camelina. Winter camelina was sown on four different dates: Date 1 (SD1), at the same sowing date as maize and soybean, Date 2 (SD2) at V4-V5 of maize and V3-V4 of soybean growth stages, Date 3 (SD3) at ‘silking’ of maize and R1-R2 stage of soybean, and Date 4 (SD4) after maize and soybean harvest. Camelina establishment into standing maize and soybean largely depended on rainfall after sowing. Camelina intersown on SD1 resulted in lower maize and soybean grain and biomass yield of 14 and 10%, respectively, whereas intersowing after SD2 had no significant effect on yield.. Camelina N accumulation varied between 24 and 59 kg N ha −1 and P accumulation ranged between 4.3 and 9.2 kg P ha −1 in the spring when sown after maize and between 14 and 57 kg N ha −1 and 1.5 and 6.9 kg P ha −1 after soybean. Results indicate that camelina intersown after V4-V5 of maize or V3-V4 of soybean stages will likely avoid competition with the primary cash crop. Camelina establishment and winter survival was best when sown after maize and soybean harvest, and tended to be greater in soybean. However, there are many unanswered questions on camelina intersowing management. New research will allow optimization of intersowing management to increase yields of both crops while enhancing ecosystem services.

Crambe (Crambe abyssinica Hochst) is an oilseed crop in the Brassicaceae family. Crambe’s ability to survive in diverse environmental conditions, its unique oil composition, the high oil content, suitability for the production of slip agents for plasticizers, the capacity to be easily included in common crop rotations, and its adaptability to equipment used for small grain cultivation has renewed the interest in this emerging crop. Crambe is considered one of the main sources of erucic acid, which can be up to 60% of its seed oil content. Erucic acid (C22:1) is a fatty acid with industrial importance since it is used to produce erucamide, key ingredient in the plastic industry. Inclusion of crambe into crop rotations can be beneficial because of its short life cycle, low fertility requirements, resistance to pest and diseases, and relative drought tolerance. Currently high erucic acid rapeseed (Brassica napus L.) (HEAR) is the principal source for erucic acid. However, the risk of contaminating food quality rapeseed (i.e., canola) by cross-pollination and the negative impact on climate, due to high inputs, are potential limitations to expand HEAR cultivation. Crambe has thus great potential to, at least, partially replace HEAR as a source of erucic acid, if the current knowledge-gap in agronomic management and crop improvement (seed yield and quality) can be addressed. Seed yield needs to be increased to be able to compete with HEAR. In addition, reducing glucosinolates and fiber in crambe meal may increase its inclusion in monogastrics rations. The objective of this review was to compile and summarize new and existing information on agricultural practices in crambe production and management to identify gaps in knowledge and areas for future research to increase the cultivation of crambe.

Forage sorghum (FS) (Sorghum bicolor (L.) Moench) is a warm-season biomass crop used as forage for hay or silage with the potential to become a bioenergy feedstock or for dual-purpose (forage and energy). The objective of this study was to screen potential forage sorghum genotypes for increased chilling tolerance and biomass productivity. Seventy-one genotypes of FS were first ranked for high to low vigor index under controlled conditions at 24, 12, and 10 &deg, C. Field experiments were also conducted on a subset of 12 genotypes in Fargo and Hickson, ND, USA, in 2017 and 2018, using two different seeding dates: early (10 May) and late (27 May). Field emergence index values were greater for the late-seeding compared with the early seeding date. Under field conditions, seed mortality and biomass yield were affected by the seeding date and biomass yield correlated with emergence index and normalized vegetative index. Chemical composition of forage sorghum biomass was not affected by the seeding dates. The results of this study suggest that some forage sorghum genotypes carry genetic traits for increased chilling tolerance and produce greater biomass yield when seeded earlier than normal, which could allow for breeding chilling tolerance into forage sorghum.

In order to reduce input costs and improve sustainability of energy/forage crops in the northern Great Plains (NGP), preceding cover crops can be included into existing annual crop systems. The objective of the study was to determine biomass yield and quality of five annual energy/forage crops, grown after six different, leguminous and non-leguminous cover crop species. The experiment was conducted at two locations, Fargo and Prosper, ND, from 2010 to 2012. The experimental design was a randomized complete block with three replicates, in a split-plot arrangement where the preceding season's cover crop was the main plot and the forage crop was the sub-plot. Six cover crops, forage pea (Pisum sativum L.) cv. Arvika, Austrian winter pea (Pisum sativum ssp. arvense (L.) Poir), hairy vetch (Vicia villosa Roth.) forage radish (Raphanus sativus var. niger) cv. Daikon, turnip (Brassica rapa var. rapa) cv. Purple Top, and forage turnip (Brassica campestris x napus) cv. Pasja, were planted no-till on 8 to 9 August in 2010 and 2011 into oat (Avena sativa L.) residue. In the following spring, five energy/forage crops, maize (Zea mays L.), forage sorghum and sweet sorghum (Sorghum bicolor L.), oat, and barley (Hordeum vulgare L.) were planted no-till onto the winter-killed cover crops residue. Results across locations and years indicated forage pea and forage radish, produced the highest dry matter yield (3.3 Mg ha−1) in the fall. Total plant N content was 116 kg N ha−1 in forage peas and 76 kg N ha−1 in forage radish, respectively. Results across locations and years indicated all energy/forage crops had greater biomass yield, and total N content when preceded by a legume cover crop compared with a non-legume or the check, in the previous year. Forage sorghum had the highest average biomass yield among the five energy/forage crops, with 17.8 Mg ha−1, followed by sweet sorghum with 15.3 Mg ha−1. In conclusion, forage pea was the most suitable cover crop to provide additional N for the subsequent crops in the NGP. Forage sorghum and sweet sorghum can be considered as the most productive energy/forage crops, especially when preceded by a legume cover crop.