Northern Corn Belt Research Articles

Planting date impact on flowering, pollinator visitation and yield of mass flowering oilseed crops in the Northern Corn Belt

Abstract Declining natural pollinator populations are a potential threat to global food supplies. Mass flowering summer annual oilseeds can provide much needed crop diversity and floral resources to support pollinator communities. We evaluated how managing planting date affects floral phenology, floral accumulation (flower coverage time × flower area), pollinator visitation, pollinator diversity and yield of nine oilseed crops. Borage (Borago officinalis L.), calendula (Calendula officinalis L.), crambe (Crambe abyssinica Hochst), cuphea (Cuphea viscosissima Jacq. × Cuphea lanceolata W. T. Aiton), echium (Echium plantagineum L.), flax (Linum usitatissimum L.), spring camelina (Camelina sativa (L.) Crantz), spring canola (Brassica napus L.) and sunflower [Helianthus annuus L.] were grown in Morris, Minnesota during the summers of 2013 and 2014. Each crop was planted on a “standard” planting date of mid‐May and additional planting dates of early May, early June and early July. Shifting planting dates affected flowering phenology, floral accumulation, pollinator visitation and crop yield. Later planting dates led to later onset of flowering for all crops and affected total floral accumulation for crambe, cuphea and echium. Pollinator visitations changed with planting date and were generally greater with the later planting dates. At least two of the four planting dates supported high yield for each crop. The ability to maintain high crop yield across a window of planting dates affords growers management options for their fields and can be used to design complementary resource pairing and improve pollinator health through crop diversification and management.

Nitrogen use in double cropping soybean with non-fertilized winter oilseed crops

Sustainable intensification of cropping systems is a strategy to increase productivity and reduce disservices of conventional agroecosystems. Camelina [Camelina sativa (L.) Crantz] and field pennycress (Thlaspi arvense L.) are winter annual oilseed crops well suited to fill the fallow period between corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] in the U.S. northern Corn Belt, but resources use could limit their addition. A 2-year study was conducted from 2015 to 2017 in the U.S. upper Midwest to evaluate the effect of double cropping on winter oilseed crops and soybean productivity and economic performance. Treatments included relay- and sequential-cropped soybean with winter camelina and field pennycress, and monocrop soybean as control. Biomass and grain yield of winter oilseed crops were not affected by cropping system. Averaged over years and cropping systems, winter camelina resulted in more biomass, nitrogen (N) uptake and grain yield by 240, 186 and 139% respectively, compared to field pennycress. Soybean biomass, N uptake and yield were higher in relay relative to sequential cropping. Relay soybean resulted in similar total grain yield (soybean + winter oilseed crop) compared to monocropped soybean. Double cropping soybean could maintain net return compared to monocropped soybean. Results indicate that double cropping winter oilseed crops with soybean can be economically viable in the U.S. upper Midwest. Yet, research aimed at optimizing yield through N and water use while improving ecosystem services is needed. Key words: camelina, pennycress, relay cropping, multiple cropping, winter oilseed DOI: 10.25165/j.ijabe.20231602.7547 Citation: Liu R H, Gregg S, Garcia y Garcia A. Nitrogen use in double cropping soybean with non-fertilized winter oilseed crops. Int J Agric & Biol Eng, 2023; 16(2): 159–164.

Cover crop and nitrogen rate management practices influence corn NDVI and nitrogen content

AbstractCover crops are rarely adopted in the northern Corn Belt because of short growing periods but could provide benefits when grown between wheat (Triticum aestivum L.) and corn (Zea mays L.). We evaluated corn normalized difference vegetation index (NDVI) and leaf N (at six leaf, ear leaf, 75% silk, and physiological maturity), over three growing seasons in response to factorial treatments of cover crop of annual ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot], radish [Raphanus sativus L.], and no‐cover control, and N rate (0×, 0.25×, 0.5×, and 1×) relative to the recommended rate based on pre‐plant soil tests (157–190 kg N ha−1). Grain N was also measured in the last study year (2016) to evaluate if leaf N indicated grain N. Radish cover crop increased corn NDVI relative to the no‐cover control, but annual ryegrass decreased NDVI relative to no‐cover control. This response to cover crop treatment suggests that radish cover crop may improve corn nutritional status. Corn receiving 1× N rate had the slowest decrease in leaf N over the growing season, but 2016 data revealed that grain from all treatments receiving some level of N had similar N content. Root biomass was also highest in the 0.5× N rate treatment and could explain the previously reported result that 0.5× N rate results in highest corn yield. Taken together, these results suggest that half the recommended N fertilizer can be used with little effect on nutritional status of corn following spring wheat in the northern Corn Belt.

Water Availability for Biorefineries in the Contiguous United States and the Implications for Bioenergy Production Distribution.

Renewable biofuel production depends on many factors, including feedstock availability, refinery and shipment infrastructure, and in particular, water availability. This study assesses water requirement and availability for mainstream biorefinery technologies in the contiguous United States (CONUS). The assessment is conducted in newly defined spatial units, namely, biorefinery planning boundaries, considering feedstock availability, transportation cost, and refinery capacity requirement for cost-effectiveness. The results suggest that the total biorefinery water use in the CONUS by 2030 will be low compared to the total water availability. However, biorefinery water requirements can aggravate the water stress situation in many regions, including the Great Plains, California Central Valley, and the upper Columbia-Snake River basin in Washington. Bioenergy productions in these regions can be largely constrained by water. It is projected that biofuel production will concentrate in Northern Plains, Lake States, and Corn Belt regions, which contribute 94.4% of the conventional, 86.1% of biodiesel, and 54.8% of cellulosic biofuel production mandated by the renewable fuel standard. If biorefineries are constrained to use less than 10% of the locally available water, up to 7% of planned cellulosic biofuel production will be affected. Findings from this study can aid the sustainable planning of national bioenergy production.

Evaluation of Agrobiodiversity and Cover Crop Adoption in Southern Ontario Field Crops

Incorporating cover crops into corn and soybean operations across Southern Ontario is essential for maintaining yields under environmental stressors. Unfortunately, amongst the literature, there is a concern about the low adoption rate of cover crops in the northern Corn Belt due to a shift toward low agrobiodiversity and dominance of more profitable corn and soybean cropping systems, encouraged by extensive use of fertilizers, herbicides, and pesticides. This study examines whether Southern Ontario is following suit in decreasing agrobiodiversity trends, at the county level, and examines the adoption of cover crops within corn and soybean operations across Southern Ontario using digital imagery from 2013 to 2018. Results reveal that Southern Ontario is indeed shifting from systems characterized by higher agrobiodiversity to systems dominated with corn, soybean, and hay. Despite the benefits of cover crops, this study reveals that most of the current corn and soybean operations are not incorporating cover crops into the rotation. More significantly, the low adoption of cover crops is most apparent in southwestern Ontario, and increases in adoption occur toward the north.

Desiccation of corn allows earlier direct seeding of winter camelina in the northern Corn Belt

AbstractIn the U.S. Upper Midwest where growing seasons are short, establishing winter annual cover crops following corn (Zea mays L.) is challenging. Winter camelina [Camelina sativa (L.) Crantz] shows promise as a winter annual cover crop that can be dual cropped with soybean [Glycine max (L.) Merr.] to help diversify the corn–soybean rotation. This 2‐yr field study in southern and western Minnesota evaluated desiccating corn with a preharvest aid to hasten its dry‐down and hence harvest so that camelina could be no‐till drilled in a timely manner. We hypothesized that direct drilling camelina following corn harvest would improve establishment and yields. Sodium chlorate was applied as a desiccant to corn at early (D1) and mid‐R5 (D2) and physiological maturity (D3) stages of development, including an untreated check. The D1 and D2 treatments hastened corn harvest by 1 to 3 wk compared with the check. Corn grain yields were unaffected by the D2 and D3 treatments, but significantly declined by 16% in D1. Camelina seed yield did not differ among desiccation treatments and averaged 815 kg ha−1 across both locations with an average oil content of 385 g ka−1. Desiccating corn hastened its harvest allowing more time to drill‐seed camelina, thus improving establishment. However, more work is needed to improve management and genetics of winter camelina for use as a cash cover crop in corn systems.

Interseeded pennycress and camelina yield and influence on row crops

AbstractField pennycress (Thlaspi arvense L.) (PC) and winter camelina [Camelina sativa (L.) Crantz] (WC) have the potential to provide ecosystem services and economic incentives when adopted as an oilseed cover crops in corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations. However, PC and WC establishment and yield in the northern Corn Belt and their subsequent impact on row crops are not well known. This study was conducted to determine the effects of interseeding dates (R4, R5, and R6; and R6, R7, and R8 development stages for corn and soybean, respectively) and cover crop species (PC, WC, and winter rye [Secale cereale L.]) on seed yield and oil content of interseeded oilseeds (PC and WC) and relay soybean, and 3rd‐year corn grain yield and quality. Study sites were initiated near Ames, IA; Morris and Rosemount, MN; and Prosper, ND. Late interseeding of PC and WC resulted in greater oilseed yield. Overall yields of PC (218–880 kg ha–1) and WC (15–770 kg ha–1), averaged across interseeding dates, were low when interseeded in corn and soybean. The PC and WC reduced relay‐soybean grain yield by 13–32% and 13–42%, respectively. Corn grain yield and quality following relay soybean were not affected by the residual effects of oilseed cover crops. Based on the results of our study, we do not recommend relay cropping soybean with PC and WC in the upper Midwest.

Pre‐Plant and In‐Season Nitrogen Combinations for the Northern Corn Belt

Core Ideas Starter fertilizer strategies must sufficiently supply N until sidedress time to influence success of in‐season N application. Applying the majority of N at V11 did not increase yield potential and may be best utilized as a rescue application in the northern Corn Belt. Increased 5×5 starter N rates (>45 kg N ha−1) may be required when full SD is applied at V11 to maintain yield potential. In variable weather conditions splitting N applications (i.e., multi‐pass systems) improved synchrony of N application with corn N uptake. In‐season N applications offer greater flexibility to address climate variability and better synchronize N availability with corn (Zea mays L.) uptake, but deliberating between V4 vs. V11 sidedress (SD) application requires validation. A six site‐year study investigated multiple N placement and timing strategies on corn growth, yield, and profitability. The three primary strategies involved pre‐plant incorporated (PPI), in‐furrow (IF) (7.8 kg N ha−1), or subsurface banded N fertilizer below the furrow (5×5) (45 kg N ha−1). Treatment combinations within the IF and 5×5 starter N strategies included SD at V4, V11, or 50:50 (split) V4 and V11. The PPI strategies involved 100% urea, 25:75 blend of urea with polymer‐coated urea, and poultry litter applied at 2.2 Mg ha−1 plus SD N at V11. There were few yield and profitability benefits to late‐season N application. The 5×5 strategy stabilized both yield and profit variability whereas the IF strategy occasionally reduced yield when SD was delayed from V4 to V11. Split N applications (i.e., multi‐pass) increased yield 4.4 to 16.1% compared with a one‐pass PPI strategy in 4 of 6 site years. Increased starter N rates (>45 kg N ha−1) may be required when full SD is applied at V11 but N source must be cost effective. When using IF and 5×5 strategies at N rates in the current study, in‐season SD N applications were required prior to V11. The V11 timing may be considered as a rescue application in northern corn regions but not standard practice.

Weed Communities in Strip-Tillage Corn/No-Tillage Soybean Rotation and Chisel-Plow Corn Systems after 10 Years of Variable Management

AbstractPrevious research has shown that strip-tillage (ST) systems conserve soil, reduce production costs, and save time for growers compared with intensive-tillage systems. In contrast to these well-documented benefits, we have limited information on weed community dynamics and management risks in ST corn (Zea maysL.) production systems in the northern Corn Belt. Therefore, we conducted research in 2015 and 2016 to characterize weed community composition, emergence patterns, and aboveground productivity in an ST corn/no-tillage (NT) soybean [Glycine max(L.) Merr.] rotation that was established in 2007 compared with a long-term intensive-tillage chisel-plow (CP) continuous-corn system. Fifteen or more weed species were identified in nontreated quadrats in each cropping system in each year. Common lambsquarters (Chenopodium albumL.) was the most abundant weed species across systems and years.Chenopodium albumdensities were similar between CP and ST corn phases and were approximately 2-fold greater compared with the NT soybean phase. Other abundant weed species occurred at much lower densities thanC. album. In each year, cumulative emergence of nontreated weed communities was described best by a logistic function in each cropping system. Maximum weed community emergence was greater in CP corn than ST corn phases in 2015, but did not differ in 2016. In the ST corn phase, most (about 75%) weed community emergence occurred in the in-row (tilled) zone compared with the between-row (nondisturbed) zone. Total late-season weed shoot biomass did not differ between nontreated CP and ST corn phases in either year, withC. albumaccounting for >85% of total weed biomass in these phases. These results suggest that weed community composition, total emergence, and productivity were similar between CP and ST corn phases after 10 yr. Our findings, coupled with previous research that showed favorable agronomic performance and greater soil conservation associated with the long-term ST corn/NT soybean system, suggest that production risks are no greater than a CP corn system, while processes that underpin ecosystem services are enhanced. These results provide strong evidence to support grower adoption of ST practices as an alternative to intensive tillage.

Early planting dates maximize winter annual field pennycress (Thlaspi arvense L.) yield and oil content

Pennycress (Thlaspi arvense L.), a common winter annual weed species in North America, has received attention in recent years as a potential oilseed feedstock for biofuel production but little is known about best practices for its production as a managed crop. Therefore, the objective of this study was to determine optimum sowing date to maximize pennycress yield, oil content, and crude protein. Four field experiments with 10 unique sowing and harvest dates over 3 crop years were conducted in Morris, MN, USA. Pennycress was no-till seeded from late August to late October at a rate of 6.7kgha−1. Seed yield averaged between 99 and 1109kgha−1 when sown in late October and early September, respectively, while oil content for the same sowing period averaged between 26.8 and 36.3%, respectively. Yield was not related to in-season environmental variables, such as cumulative precipitation, soil temperature at planting, or accumulated photohydrothermal time. However, oil content was maximized under greater precipitation (r2=0.86), warmer soil temperatures (r2=0.62) and greater photohydrothermal time when modeled at 2, 4, 6, 8, 25, 50 and 100cm soil depths (between r2=0.53 to r2=0.85). Results indicate that environment conditions favoring a long maturation period increased oil accumulation in seeds. Conversely, a longer growth period reduced seed crude protein. Although pennycress protein is expected to have industrial uses, managing for yield and oil content is preferred. Therefore sowing pennycress in late August through September in the northern Corn Belt will maximize yields and oil content.

Corn Residue Use by Livestock in the United States

Core Ideas USDA‐ERS surveyed 2250 producers from 19 states on corn residue grazing and mechanical harvests in 2010. Approximately 4.06 million ha was grazed by 11.7 million head of livestock. Approximately 0.81 million ha of corn residue was mechanically harvested in 2010. Corn residue is a significant resource for integrated crop–livestock systems in the western Corn Belt. Corn (Zea mays L.) residue grazing or harvest provides a simple and economical practice to integrate crops and livestock, but limited information is available on how widespread corn residue utilization is practiced by US producers. In 2010, the USDA Economic Research Service surveyed producers from 19 states on corn grain and residue management practices. Total corn residue grazed or harvested was 4.87 million ha. Approximately 4.06 million ha was grazed by 11.7 million livestock (primarily cattle) in 2010. The majority of grazed corn residue occurred in Nebraska (1.91 million ha), Iowa (385,000 ha), South Dakota (361,000 ha), and Kansas (344,000 ha). Average grazing days ranged from 10 to 73 d (mean = 40 d). Corn residue harvests predominantly occurred in the central and northern Corn Belt, with an estimated 2.9 Tg of corn residue harvested across the 19 states. This survey highlights the importance of corn residue for US livestock, particularly in the western Corn Belt.

Camelina growth and yield response to sowing depth and rate in the northern Corn Belt USA

Camelina (Camelina sativa L.) is gaining interest as a productive alternative oilseed crop for biofuels, bioproducts, and healthy food-use applications. Developing sound agronomic practices for its production is key to optimizing its seed oil yield potential. Plant stand establishment of camelina has been problematic in some environments, which may be related to its small seed size and current recommendation for shallow sowing. Shallow sowing can diminish seed to soil contact and expose seeds to large soil temperature and moisture fluctuations, which greatly affect germination and seedling emergence. A study was conducted in 2011 and 2012 on a Barnes loam soil in western Minnesota to examine the effects of sowing spring camelina at soil depths of 1, 2, and 4cm at sowing rates of 2, 3, and 6kgha−1. Seedling emergence increased with sowing rate, but averaged across depths it had no effect on seed yield. Seedling emergence between the 1 and 2cm sowing depths did not differ in 2012, while stands were reduced by an average of 29% at the 2cm depth in 2011, but seed yields did not differ between the two sowing depths in either year. However, averaged across sowing rates, sowing at 4cm led to a 64% stand reduction and a significant 22% loss of yield compared with the 1 and 2cm depths. Neither sowing depth nor rate affected seed oil content or harvest index. Results show that camelina has exceptional yield compensation capacity at low plant densities and can be sown deeper than commonly recommended (i.e., ≤1.0cm) without compromising yield in the northern Corn Belt. Sowing to a depth of 2cm may be beneficial for certain soils prone to large temperature and moisture fluctuations.

A Watershed Level Economic Analysis of Cellulosic Biofuel Feedstock Production with Consideration of Water Quality

<p>National policy supports the production of renewable energy from cellulosic feedstocks such as corn stover and switchgrass. These feedstocks have contrasting impacts on water quality. In this study, the regional supply response for cellulosic biofuel from these two feedstocks is estimated for the Le Sueur Watershed in South-Central Minnesota. The impacts of the resulting agricultural production activities on water quality in this northern corn belt watershed are also estimated. The Le Sueur River is a tributary of the Minnesota River, which in turn feeds into the Mississippi. The analysis is conducted with a multi-region, endogenous supply, mathematical programming model of the agriculture sector in the watershed. A unique aspect of the analysis is the spatial detail used in the production model. Results from a previous simulation analysis conducted with the Soil Water Assessment Tool (SWAT) model are used in the economic model to simulate the effects of the feedstock supply response on water quality in the Le Sueur. Sediment and nutrient losses from corn stover production make switchgrass more promising on environmental grounds, but the relatively high cost of production causes switchgrass to cover only a small part of crop land if farmers have unrestricted choice about how to supply cellulosic feedstocks.</p>

Registration of the OhW (Oh43×W64A) Maize Recombinant Inbred Mapping Population

The Oh43×W64A (OhW) maize (Zea mays L.) mapping population (MP‐3, NSL 511549 MAP) consists of 255 recombinant inbred lines (RILs). This mapping population was constructed from a cross between inbred lines Oh43 (Ames 19288) and W64A (PI 587152). Our primary goal was to develop a mapping population segregating for a large number of important agronomic traits using a cross of lines that formed a heterotic hybrid used in the northern Corn Belt. Genetic markers were scored using genotyping‐by‐sequencing technology, and a high‐density genetic map was constructed using the single nucleotide polymorphism data. A wide range of phenotypic diversity among individuals, and transgressive segregation, was observed for all traits measured. The registration of this RIL mapping population provides geneticists and breeders with a highly diverse set of lines in combination with a dense genetic map that can be utilized to identify quantitative trait loci at high mapping resolution.

Wheat improves nitrogen use efficiency of maize and soybean-based cropping systems

Integrated nitrogen (N) management strategies could make significant contributions to improving the efficiency of N use in the northern Corn Belt, particularly for maize, which has high N requirements. Using legume cover crops has been shown to increase both the soil's capacity to supply N and nitrogen use efficiency (NUE), through the reduction in the amount of N fertilizer that must be applied to the following crops. However, the impact of non-legume crops such as winter wheat (Triticum aestivum L.) on the diminishing return function between crop yield and N supply and its influence on N fertilizer use remains unclear. We hypothesized that maintaining wheat in short maize and soybean- based rotations is instrumental to improve cropping system performance and increase N fertilizer use efficiency while decreasing N requirements for maize. Seven maize and soybean rotations with different frequency of winter wheat with or without underseeded red clover (Trifolium pratense L.) were grown in two tillage systems (conventional and zone-tillage) and four long-term N regimes in Ridgetown, ON, Canada (2009–2013). Wheat in the rotation increased maize and soybean yields, negated crop yield lags due to zone-tillage, and decreased maximum economic rates of fertilizer N (MERN). The benefits of wheat in the rotation on maize yield were negated by high N rates; however, similar yields were obtained with lower N levels in rotationally grown maize, resulting in a 17% (conventional till) to 21% (zone-till) increase in partial factor productivity for N fertilizer at MERN (PFPMERN). While N benefits to crops following wheat alone may be attributed to a higher indigenous plant available soil N, underseeding red clover further increased the agronomic efficiency (AE) of N fertilizer (AEMERN) up to 32%. Maize yields were also less limited by N supply and less responsive to N fertilization when grown in rotation with wheat, especially in the zone-till system. These results highlight the value of wheat as a system component of dominant maize/soybean short rotations of Ontario and its potential to increase both maize and soybean productivity using less N input.

Water Use in Camelina–Soybean Dual Cropping Systems

Global population growth is increasing the demand for food, feed, fiber, and fuel. Recently, we reported that winter camelina (Camelina sativa L.) can be feasibly double‐ (DC) and relay‐cropped with soybean [Glycine max (L.) Merr.] in the northern Corn Belt region as an option for sustainably intensified crop production. However, water availability can be a limiting factor for dual crop systems. Therefore, the present study determined seasonal water use in various winter camelina–soybean dual crop systems that included two sequential DC and two relay‐crop treatments compared with a full‐season monocropped soybean (Mono‐Soy). The rooting characteristics of camelina were also evaluated. The study was conducted on a Barnes loam soil (fine‐loamy, mixed, superactive, frigid Calcic Hapludoll) in west central Minnesota over two growing seasons in 2010 and 2011. Camelina had a meager root system with 82% of its root density found in the top 0.3 m of soil. Although both DC and relay‐crop treatments used more seasonal water than a sole soybean crop, on average it was only 26 and 50 mm greater in 2010 and 2011, respectively. Camelina is a low water user compared with soybean. Total cropping system water use efficiency for relay‐cropping was comparable to the sole soybean crop, but for the DC treatments was less. This cropping strategy is a way to sustainably integrate food and fuel production to meet societal needs of a growing population. Moreover, our results indicate that it may be amenable to most rainfed‐farming areas in the upper Midwest where soybean is grown.

Responses of Canopy Reflectance, Light Interception, and Soybean Seed Yield to Replanting Suboptimal Stands

ABSTRACTSoybean [Glycine max (L.) Merr.] planting date trends have steadily shifted earlier within the northern Corn Belt, while inclement weather, insect pressure, and disease pressure associated with spring planting can result in replanting some years. However, limited published literature exists about soybean replant thresholds for suboptimal plant stands and the effects of seed treatments on this decision. This study evaluated three planting dates, three seed treatments, and twelve seeding rate–replant combinations to determine replant thresholds in terms of maximizing seed yield, the effects of seed treatments on these thresholds, and the relationship of cumulative intercepted photosynthetically active radiation (CIPAR) and cumulative normalized difference vegetative index (CumNDVI) on seed yield. Trials were conducted during 2012 and 2013 in southern Wisconsin. Soybean planting in early May increased seed yield by 358 kg ha−1 compared with late May and by 805 kg ha−1 compared with mid‐June. Seed yield reductions were due to decreased seeds m−2 while CIPAR and CumNDVI measurements may partially explain this planting date effect. When initial plant stands were below threshold (<247,000 plants ha–1), filling in these stands with enough seed to bring the final plant stand above the threshold increased yield, whereas using tillage and replanting the entire stand only increased yield when initial plant stands were extremely low (<91,000 plants ha−1). Yield was related to both CIPAR (R2 = 0.54) and CumNDVI (R2 = 0.49) and the latter two variables were highly correlated (r = 0.89). We observed linear yield increases through 700 MJ m−2 of CIPAR; therefore, management practices to increase CIPAR should be used. This study showed that early May planting with a fungicide/insecticide seed treatment (CruiserMaxx) and generating adequate plant stands (>247,000 plants ha−1) maximized CIPAR.

Agroecological Approaches to Mitigate Increasing Limitation of Corn Yields by Water Availability

A key strategy for climate change adaptation in the rain-fed northern Corn Belt is to decrease cropping system vulnerability to changes in precipitation patterns by building resilience. Using 50- year of county level yield and environmental data from Iowa and Ontario, we first demonstrate that sensitivity of corn yield to precipitation, particularly in July and August, has increased over the past five decades despite no changes in precipitation patterns. This can be attributed to steady improvement in corn yield potential and so plant water demand since the mid-20th century and removal of non-water constraints to crop production. Such vulnerability of corn-based cropping systems to water limitations is of increasing concern as climate change models predict higher summer temperatures and year-to-year variations in precipitations in this region. As suggested in the ecology literature, increasing agroecosystem temporal and spacial diversity is one of the key management strategies to deal with impending weather variability. Using yield and environmental data from a 30-year long-term rotation and tillage trial in Ontario, we show that diversification of short corn-based rotations using small grains and forage crops increases corn yield stability and resilience to both limiting and excess soil moisture1. We also demonstrate the importance of conservation tillage and measured the impact of rotation and tillage history on plants ability to access water resources, plant available soil water and their combined effects on timing of physiological water stress and grain yield when drought occurs at reproductive stages. Our results emphasize the growing importance of developing strategies for managing soil moisture in rain-fed regions and the significance of agroecological approaches to develop hardy agricultural systems and protect food and feed production against the upcoming extreme weather events.

Dual Cropping Winter Camelina with Soybean in the Northern Corn Belt

Sustainably balancing biofuel crop production with food, feed, and fiber on agricultural lands will require developing new cropping strategies. Double‐ and/or relay‐cropping winter camelina (Camelina sativaL.) 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‐field energy balance of winter camelina–soybean 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 unaffected by cropping system and ranged from 1.1 to 1.3 Mg ha−1. Relay‐cropped soybean yields were greater than double‐cropped soybean and were 58 to 83% of that for the monocropped control. Seed oil and protein content of double‐ and relay‐cropped 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 efficiency (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.

Aerially seeding cover crops in the northern US Corn Belt: Limitations, future research needs, and alternative practices

I ncorporating cover crops into the two-year corn ( Zea mays L.)–soybean ( Glycine max L.) rotation can reduce soil erosion, increase soil organic matter, improve soil structure (Snapp et al. 2005), and reduce nitrate (NO3) leaching (Strock et al. 2004; Fisher et al. 2011). However, it is often difficult to establish winter cover crops in the cooler climate and shorter growing season of the northern Corn Belt. Miguez and Bollero (2005) reported that grass cover crops in the north central United States would only provide marginal benefits due to low biomass production. Through growth simulations, Baker and Griffis (2009) found that the main limitations are degree days and photosynthetically active radiation. Strock et al. (2004) suggested that based on average weather patterns in southwestern Minnesota, winter rye ( Secale cereal L.) would only be a successful cover crop in one out of four years. In these studies, however, temperatures were already cool when the cover crop was planted following harvest of the preceding crop. As another option, Frye et al. (1988) suggested that broadcasting seed into a standing crop can result in earlier crop growth than drilling the seed after harvest. Through growth simulations based on field experiments, Feyereisen et al. (2006) recommended…