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Crown buds of field-grown leafy spurge ( Euphorbia esula L.) were examined to determine relationships between carbohydrate metabolism and gene expression throughout para-, endo-, and eco-dormancy during the transition from summer, autumn, and winter, respectively. The data indicates that endo-dormancy plays a role in preventing new shoot growth during the transition from autumn to winter. Cold temperature was involved in breaking endodormancy, inducing flowering competence, and inhibiting shoot growth. An inverse relationship developed between starch and soluble sugar (mainly sucrose) content in buds during the shift from para-to endo-dormancy, which continued through eco-dormancy. Unlike starch content, soluble sugars were lowest in crown buds during para-dormancy but increased over two-to three-fold during the transition to endo-dormancy. Several genes ( AGPase , HK , SPS , SuSy , and UGPase ) coding for proteins involved in sugar metabolism were differentially regulated in conjunction with welldefined phases of dormancy in crown buds. Marker genes for S-phase progression, cell wall biochemistry, or responsive to auxin were also differentially regulated during transition from para-, endo-, and eco-dormancy. The results were used to develop a model showing potential signalling pathways involved in regulating seasonal dormancy status in leafy spurge crown buds.

Sustainably balancing biofuel crop production with food, feed, and ber on agricultural lands will require developing new cropping strategies. Double-and/or relay-cropping winter camelina (Camelina sativa L.) with soybean [Glycine max (L.) Merr.] may be a means to produce an energy and food crop on the same land in a single year. A study was conducted between 2009 and 2011 in west central Minnesota to evaluate yields, seed quality, economics, and within-eld energy balance of winter camelinasoybean double-and relay-cropping systems compared with a conventional monocropped full-season soybean. Systems included methods to hasten camelina harvest (e.g., swathing and desiccating) to promote early soybean growth. Camelina seed yields were una ected by cropping system and ranged from 1.1 to 1.3 Mg ha -1 . Relay-cropped soybean yields were greater than doublecropped soybean and were 58 to 83% of that for the monocropped control. Seed oil and protein content of double-and relaycropped soybean were comparable to their monocropped counterpart and combined seed oil yield for the dual crop systems was as much as 50% greater. Net economic returns for the relay-crop treatments were competitive with that of the full-season soybean. Moreover, net energy of the relay-crop treatments was generally as high as the sole soybean crop, but energy e ciency (outputs/ inputs) was less due to greater inputs. Results indicate that dual cropping of winter camelina with soybean is agronomically viable for the upper Midwest and might be an attractive system to growers seeking a "cash" cover crop.

Camelina (Camelina sativa L.), a member of the Brassicaceae family, can potentially serve as a low‐input alternative oil source for advanced biofuels as well as food and other industrial uses. Winter annual camelina genotypes may be economically and environmentally advantageous for the northern Corn Belt, but little is known about their agronomic potential for this region. A 2‐yr field study was conducted in western Minnesota to determine optimum fall sowing time for yield and oil content of two winter camelina cultivars in a no‐tillage (NT) and chisel‐plowed (CP) system. Seeding dates ranged from early September to mid‐October. Plants reached 50% flowering as much as 7 d earlier in the NT than the CP system. Plant stands were generally greatest in the NT system, but yields were only greater than those in the CP system during the second year of the study, possibly due to differences in water logging of soil between tillage systems. Seed yield and oil content increased with sowing date up to early October. When sown in October, seed yield and oil content ranged from 419 to 1317 kg ha−1 and 282 to 420 g kg−1, respectively. Results indicate that camelina is a viable winter crop for the northern Corn Belt and that seed yields and oil content tended to be greatest when sown in early to mid‐October. Moreover, fall‐seeded camelina offered good weed suppression without the use of herbicide, supporting the contention that it can be successfully produced with low agricultural inputs.

Many environmental benefits accrue from reducing tillage and increasing crop diversity; however, economic factors often encourage the continued use of intensive tillage and specialized crop production. This study examined crop yields, input costs, and economic returns during the transition to a range of cropping system alternatives in the northern Corn Belt region, including different system (organic, conventional), tillage (conventional, strip-tillage), rotation (corn-soybean, corn-soybean-wheat/alfalfa-alfalfa) [Zea mays L., Glycine max (L.) Merr., Triticum aestivum L., Medicago sativa L.], and fertility (no fertilizer/manure, fertilizer/manure applied at recommended rates) treatments. Increasing crop diversity and reducing tillage intensity reduced total costs by $24-102 ha 21 within conventional treatments, and $16-107 ha 21 within organic treatments. Yields of corn, soybean, and wheat were more than 15% lower when using organic vs. the highest yielding conventional practices. Treatments receiving fertilizer or manure had wheat yields more than 0.3 Mg ha 21 and alfalfa yields 2.7 Mg ha 21 higher than treatments that did not receive fertilizer or manure. Within conventional systems, no significant differences in the 4-yr net present value of net returns were detected for tillage and rotation alternatives. Net present values for the organic systems without organic price premiums were at least $692 ha 21 lower than for the best conventional systems suggesting a barrier to the adoption of these systems should organic price premiums decline. However, when organic price premiums were included, most organic treatments had net present values comparable to or exceeding those from conventional treatments.

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The limited time available for cover crop establishment after maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] harvest is one of the main reasons for low cover crop adoption in the upper Midwest. Therefore, a 2-yr multilocation study was conducted to evaluate winter annual cover crops establishment, their effect on main crop grain yields, and soil water content when interseeded into standing maize and soybean. Treatments were three interseeding dates (broadcasting at R4, R5, and R6 growth stages for maize, and R6, R7, and R8 for soybean) and three cover crops (win-winter rye [Secale cereale L.] plus a no cover crop control). Cover crop establishment and growth varied with interseeding date across locations and seasons for both maize and soybean systems. Averaged over the years, rye produced more green cover and biomass than the oilseeds in spring. However, at the northern-most site, the greatest (40%) green cover was recorded from pennycress and indicates its potential as a cover crop. Seeding date and cover crops did not negatively affect maize or soybean grain yields or soil water content. Generally, cover crop establishment and growth were better in the soybean system than maize due to better light penetration. Further research is needed to develop better suited cultivars and/or agronomic management practices for interseeding into maize. The results of this study indicate that producers could integrate these covers to diversify and add ecosystem services to soybean production practices.Abbreviations: PAR, photosynthetic active radiation; PC, pennycress; PLS, pure live seeds; PPD, plant population density; WC, winter camelina.