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Macropartisanship is a measure of aggregate trends in party identification in the mass public that allows researchers to track partisanship dynamically. In previous research, macropartisanship was found to vary in concert with major political events and forces like presidential approval and the economy. However, studying macropartisanship as an aggregate trend assumes that group dynamics within the measure are equivalent. We present a series of new measures of macropartisanship using Stimson’s (2018) dyad ratio approach disaggregated by race and ethnicity. We detail the creation of measures for White, Latino, and Black macropartisanship from 1983 to 2016 using more than 500 surveys from CBS News and CBS/New York Times. The resulting data collection is publicly available and can be downloaded in monthly, quarterly, or yearly format. Our initial analysis of these data show that thinking about macropartisanship as a single aggregate measure masks important and significant variation in our understanding of party identification. Change in the measures are uncorrelated. Latino macropartisanship is more volatile and responds more to economic conditions, Black macropartisanship is very stable and has become more Democratic in response to increased polarization, while White macropartisanship has become less responsive to economic conditions as has become more Republican as Republicans have moved to the right.

Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity. Foundation for Food and Agricultural Research [523926]; Samuel Roberts Noble Foundation; General Mills Published version Foundation for Food and Agricultural Research (grant ID 523926), General Mills, and The Samuel Roberts Noble Foundation.

There is mounting concern that selection and breeding of native grasses for greater biomass production could promote weediness. Yet little is known about the invasion potential or ecological impacts of such selectively bred native grasses. Here we focus on cultivars of native switchgrass (Panicum virgatum L.) that have undergone selection, breeding, and intraspecific hybridization to improve agronomic traits for biomass production. We evaluated the competitive effects of switchgrass cultivars (EG-2101 and ‘Trailblazer’) and wild switchgrass populations on two native prairie grasses [sideoats grama, Bouteloua curtipendula (Michx.) Torr., and Canada wild rye, Elymus canadensis L.] across a gradient of switchgrass density in a greenhouse. Cultivars produced 48–128% more biomass and reduced sideoats grama biomass by 25–59% more than wild switchgrass. Effects of switchgrass cultivars on Canada wild rye were minimal compared to sideoats grama. Later flowering and larger seed size of cultivars may be contributing to their greater biomass and competitive effects on sideoats grama. These data suggest that breeding switchgrass for enhanced biomass yield may increase competitive effects on some native grasses. Further studies are merited to test the potential for switchgrass biomass cultivars to spread and impact species diversity of restored and remnant native plant communities.

Shrub willow has potential for being a viable dedicated bioenergy crop in temperate northern latitudes of the USA. Selection of high-producing willow cultivars is critical for economic viability and long-term sustainability of willow production systems. Long-term trials are needed in different geographic areas to better understand genetic by environment interactions on biomass yield for greater profitability and to enhance future breeding efforts. Field trials were conducted in two contrasting environments, northern New York and southern Minnesota, to explore changes in shrub willow yield ranking over three harvest cycles across a range of cultivars and diversity groups. Overall, the MN site produced higher, more stable biomass yields than the NY site due primarily to more productive soils, warmer climate, and less weed pressure. However, between-site differences in willow biomass yield were nominal after the second harvest cycle. Yield variability among the top five willow cultivars at each harvest was significantly less than variability among all cultivars regardless of site. Shrub willow cultivars identified in the top-ranking groups were different between sites. Results show that willow can be a viable long-term crop for sustained biomass feedstock production across a wide range of soils and climates but proper cultivar selection is critical for biological and economic success.

Understanding the nature and degree of competition between trees and co-planted crops in agroforestry systems can inform management decisions, future species selection, and system design. We measured variation in herbaceous biomass yield, photosynthetically active radiation (PAR), soil water potential, and residual soil NO3 in alley cropping systems consisting of prairie cordgrass (Spartina pectinata) or an 11-species native grass-forb-legume polyculture planted between rows of shrub willow (Salix purpurea L. ‘Fish Creek’) at two Minnesota sites. At Empire, biomass yield increased with distance from the tree row for both alley crops, as did PAR and NO3 availability. At Granada, no spatial pattern in crop yield was evident, despite reduced PAR and NO3 availability adjacent to tree rows. At both sites, patterns in soil water potential suggested that trees competed with crops for soil water within 2.4 m of tree rows, but had a facilitative effect on crop water use at 4.8 m. Alleys had differing cardinal orientations at the two sites, and light availability was lower in a north–south alley (Empire) than in west–east and northwest-southeast orientations (Granada). At Empire, mixed effects analysis indicated that competition for light and soil water were responsible for reductions in crop yield. For every 100 μmol m−2 s−1 increase in PAR, model estimated herbaceous crop yield increased by 623 kg DM ha−1. For every 20 kPa increase in average daily water potential, crop yield increased by 1038 kg DM ha−1. The relative impact of competition on biomass yield was similar for both crops, though prairie cordgrass had higher average yields at Empire. Similar alley systems should avoid north–south alley orientations to minimize competition for light.

Living snow fences are windbreaks designed to prevent blowing snow on transportation routes in cold climate regions. Currently, there is a need to diversify plant species used in living snow fences due to landowner concerns about establishment and growth. Recent studies have suggested that fast-growing shrub willows (Salix spp.) can provide affordable and easily established living snow fences. We sought to compare the growth and establishment of four shrub willow cultivars and one native shrub willow species to two shrub species—gray dogwood (Cornus racemosa Lam.) and American cranberrybush (Viburnum opulus L. var. americanum Ait.)—traditionally used for living snow fences in Minnesota, as well as evaluate different coppice dates within willow species. After two years of growth, we found all species to have survival rates of >80% except for S. eriocephala × S. eriocephala ‘S25’ (77%). Additionally, postcoppice growth in 2014 for the willows significantly exceeded the growth of the traditional living snow fence species by up to 4.8-fold. Within willows, coppice date (fall of 2013 versus spring of 2014) had no effect on the survival and growth of plants except for S. purpurea ‘Fish Creek’ and S. eriocephala × S. eriocephala ‘S25’, which responded differently to coppice dates. Lastly, the native willow species S. petiolaris had comparable growth to the tallest and greatest stem-producing willow cultivars S. purpurea × S. miyabeana ‘Oneonta’ and S. purpurea ‘Fish Creek’. These results suggest that willows may establish faster than traditional living snow fence species; certain native shrub willow species may be as suitable as shrub willow cultivars for living snow fences, and the best coppice time for willow living snow fences may depend on species and objectives.

In the midwestern United States, biotypes of giant ragweed resistant to multiple herbicide biochemical sites of action have been identified. Weeds with resistance to multiple herbicides reduce the utility of existing herbicides and necessitate the development of alternative weed control strategies. In two experiments in southeastern Minnesota, we determined the effect of six 3 yr crop-rotation systems containing corn, soybean, wheat, and alfalfa on giant ragweed seedbank depletion and emergence patterns. The six crop-rotation systems included continuous corn, soybean–corn–corn, corn–soybean–corn, soybean–wheat–corn, soybean–alfalfa–corn, and alfalfa–alfalfa–corn. The crop-rotation system had no effect on the amount of seedbank depletion when a zero-weed threshold was maintained, with an average of 96% of the giant ragweed seedbank being depleted within 2 yr. Seedbank depletion occurred primarily through seedling emergence in all crop-rotation systems. However, seedling emergence tended to account for more of the seedbank depletion in rotations containing only corn or soybean compared with rotations with wheat or alfalfa. Giant ragweed emerged early across all treatments, with on average 90% emergence occurring by June 4. Duration of emergence was slightly longer in established alfalfa compared with other cropping systems. These results indicate that corn and soybean rotations are more conducive to giant ragweed emergence than rotations including wheat and alfalfa, and that adopting a zero-weed threshold is a viable approach to depleting the weed seedbank in all crop-rotation systems.

Any discussion of the thaw in U.S.-Cuban relations must address China’s key role in Cuba’s political and economic structure. Today, China is not only a longtime supporter of the regime but also Cuba’s largest trading partner. Perhaps more importantly, the thaw in Sino-U.S. relations and subsequent shift in Chinese economic policy offers a potential model to the Cuban communist regime, a “moral inspiration” that encourages openness to the international economy, while maintaining internal control. This chapter examines the ways China’s direct economic and political interactions with the Cuban government facilitate further economic opening, while maintaining state control over key political and economic sectors. The chapter also examines the limits of the Chinese model and its implications for Cuba’s future.

The incorporation of cover crops into the maize (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation in the U.S. upper Midwest may improve sustainability. Long, cold winters in the region make identifying successful cover crop species and management practices a challenge. Two experiments were conducted in Minnesota, USA from fall 2016 through spring 2019 to examine the effect of cover crops interseeded at four- to six-leaf collar (early-interseeded) and dent to physiological maturity (late-interseeded) on biomass and grain yield of maize. Annual ryegrass (Lolium multiflorum L.) and cereal rye (Secale cereale L.) were evaluated as monocultures and in mixtures with crimson clover (Trifolium incarnatum L.) and forage radish (Raphanus sativus L.). Differences in canopy cover and biomass of late-interseeded cover crops were observed at the southernmost location in 2018. Additional accumulated growing-degree days in fall 2018 did not translate into increased cover crop canopy coverage of late-interseeded cover crops. Differences in cover crop canopy cover and biomass of early-interseeded cover crops were observed by fall frost at all locations in 2017 and at the northernmost location in 2018. Cover crop canopy cover and biomass at termination before planting maize, soil moisture at maize planting as well as maize aboveground biomass and yield were not affected by spring cereal rye regrowth of cover crops late-interseeded the previous year. Similarly, early-interseeded cover crops did not affect maize aboveground biomass or yield. We attribute these results to limited cover crop growth. This highlights the potential of a variety of cover crop strategies interseeded into maize in the U.S. upper Midwest; however, efforts to fine-tuning cover crop management and weather conditions are needed to benefit from such practice.

Historically, agroecosystems have been designed to produce food. Modern societies now demand more from food systems—not only food, fuel, and fiber, but also a variety of ecosystem services. And although today's farming practices are producing unprecedented yields, they are also contributing to ecosystem problems such as soil erosion, greenhouse gas emissions, and water pollution. This review highlights the potential benefits of perennial grains and oilseeds and discusses recent progress in their development. Because of perennials' extended growing season and deep root systems, they may require less fertilizer, help prevent runoff, and be more drought tolerant than annuals. Their production is expected to reduce tillage, which could positively affect biodiversity. End-use possibilities involve food, feed, fuel, and nonfood bioproducts. Fostering multidisciplinary collaborations will be essential for the successful integration of perennials into commercial cropping and food-processing systems.

Development of dedicated bioenergy crop production systems will require accurate yield estimates, which will be important for determining many of the associated environmental and economic impacts of their production. Shrub willow (Salix spp) is being promoted in areas of the USA and Canada due to its adaption to cool climates and wide genetic diversity available for breeding improvement. Willow breeding in North America is in an early stage, and selection of elite genotypes for commercialization will require testing across broad geographic regions to gain an understanding of how shrub willow interacts with the environment. We analyzed a dataset of first-rotation shrub willow yields of 16 genotypes across 10 trial environments in the USA and Canada for genotype-by-environment interactions using the additive main effects and multiplicative interactions (AMMI) model. Mean genotype yields ranged from 5.22 to 8.58 oven-dry Mg ha−1 yr−1. Analysis of the main effect of genotype showed that one round of breeding improved yields by as much as 20% over check cultivars and that triploid hybrids, most notably Salix viminalis × S. miyabeana, exhibited superior yields. We also found important variability in genotypic response to environments, which suggests specific adaptability could be exploited among 16 genotypes for yield gains. Strong positive correlations were found between environment main effects and AMMI parameters and growing environment temperatures. These findings demonstrate yield improvements are possible in one generation and will be important for developing cultivar recommendations and for future breeding efforts.

Living snow fences (LSFs) are a cost-effective windbreak practice designed to mitigate blowing and drifting snow problems along transportation routes. Shrub-willows (Salix spp.) have been proposed as a LSF species to provide multiple benefits, given their potential to reach effective heights and densities soon after planting and provide a marketable biomass product. However, information regarding their establishment and snow storage capacity in LSF settings is limited. We investigated establishment and potential snow storage capacity of three shrub-willow varieties in LSF planting arrangements of two and four rows after one growing season post-coppice on a two-year-old root system in south-central Minnesota, USA. We found willows had an average survival of 89 %, an average height of approximately 1 m, and potential snow storage capacities ranging from 1 to 9 t m−1. Compared to the mean annual snow transport of the south-central region (39.9 t m−1), none of the willow LSF varieties and planting arrangements were able to trap all of the predicted blowing snow at the study site after two growing seasons post-coppice. However, using willow LSF models, we observed that willow LSFs could exceed local snow transport after 2–3 growing seasons post-coppice. Additionally, four-row willow LSF arrangements trapped approximately 20 % more snow than to two-row arrangements, and willow variety did not affect snow storage. These results add to the limited literature on shrub-willow LSFs and can guide the design of effective willow LSFs.

Integrating remote sensing data into crop models offers opportunities for improved crop yield estimation. To compare site-specific yield estimation accuracy of a stand-alone crop model with a data-integration approach, a study was conducted in 2016&ndash, 2017 with nitrogen (N)-fertilized and unfertilized treatments across a heterogeneous 7-ha maize field. For each treatment, yield data were grouped into five classes resulting in 109 spatial zones. In each zone, the Crop Environment Resource Synthesis (CERES)-Maize model was run using the GeoSim plugin within Quantum GIS. In the data integration approach, maize biomass values estimated using satellite imagery at the five (V5) and ten (V10) leaf collar stages were used to optimize the total soil nitrogen concentration (SLNI) and soil fertility factor (SLPF) in CERES-Maize. Without integration, maize yield was simulated with root mean square error (RMSE) of 1264 kg ha&minus, 1. Optimization of SLNI improved yield simulations at both V5 and V10. However, better simulations were obtained from optimization at V10 (RMSE 1026 kg ha&minus, 1) as compared to V5 (RMSE 1158 kg ha&minus, 1). Optimization of SLPF together with SLNI did not further improve the yield simulations. This study shows that integrating remote sensing data into a crop model can improve site-specific maize yield estimations as compared to the stand-alone crop modeling approach.

The idea that noncrop habitat enhances pest control and represents a win–win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win–win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies., This work was supported through the National Socio-Environmental Synthesis Center (SESYNC) National Science Foundation Award DBI-1052875 for the project “Evidence and Decision-Support Tools for Controlling Agricultural Pests with Conservation Interventions” organized by D.S.K. and R.C.-K

Yield is a critical factor in the development and understanding of willow biomass crops which experience multiple harvests after planting. Small changes in yield can have substantial impacts on economic and environmental assessments. Studies have reported increases between first rotation yield (FRY) and second rotation yield (SRY); however, there is minimal agreement on the variation of this increase. This study analyzes FRYs and SRYs of commercial willow cultivars in 360 research plots across five sites in the Northeast and North Central USA. Mean FRYs were 9.6 Mg ha−1 year−1 and mean SRYs were 7.9 % greater at 10.3 Mg ha−1 year−1. The relative change in yield between rotations was high for plots with low FRYs, but decreased as FRY increased and was negative when FRYs were highest. Therefore, applying a single yield increase factor to all willow crops may result in errors. Linear and logistic regression modeling were used to predict the magnitude of yield change across the range of FRYs and the probability for increasing/constant yields. Results showed that FRY alone predicts yield change with an R 2 of 0.635, and adding cultivar and site/management factors increases R 2 to 0.697. One study limitation is that many plots with the highest FRYs came from a drought influenced site. A meta-analysis of literature data revealed that this pattern of decreasing relative gains as FRYs increase is widespread though not previously addressed. Acknowledging this pattern should provide more accurate yield estimates over multiple rotations.

The circumstances and potential for insects to damage perennial bioenergy crops is not well understood in the United States. In this study, we evaluated the spillover and herbivory of eastern tent caterpillars (Malacosoma americanum) from host trees onto short rotation coppice (SRC) willow bioenergy crops (Salix sp.). Host trees were all in the Rosaceae family and included Prunus americana, Prunus virginiana and Malus sp. Willow showed greater leaf herbivory with increasing proximity to a defoliated host tree, suggesting that tent caterpillars spilled-over to willow after denuding their host. More tent caterpillar herbivory was associated with greater mortality of willow. This study suggests that landscape context and spatial position of host trees is important to the early establishment of a willow bioenergy crop.

The management of the soybean aphid Aphis glycines Matsumara is a major challenge to soybean production in the north-central United States. The identification and characterization of the insect predator community has informed integrated pest management strategies by providing insight on predators that can suppress soybean aphid populations. Hoverflies (Diptera: Syrphidae) are known predators of A. glycines, but more information is needed on their diversity, abundance, and performance to evaluate their importance as biological control agents of A. glycines. In this study, syrphid abundance was evaluated across two growing seasons in four soybean fields in east-central Minnesota. Six methods were used to quantify syrphid abundance at the larval, pupal, and adult life stages; describe species composition and richness for adults; and directly compare larval abundance to aphid abundance. The syrphid community comprised eight species, dominated by Toxomerus marginatus (Say) and Toxomerus geminatus (Say). Syrphid abundance was relatively low in soybean fields. Feeding trials were conducted to compare the performance of the most common syrphid (T. marginatus) on a diet of A. glycines with two native aphids, Aphis nerii Boyer de Fonscolombe and Aphis monardae Oestlund. Despite their low abundance in soybeans, T. marginatus larvae perform well on A. glycines, A. nerii, and A. monardae in laboratory feeding trials, implying that factors other than host suitability are limiting their potential to exert biological control on soybean aphids.

Various local factors influence the decision of when to harvest grassland biomass for renewable energy including climate, plant composition, and phenological stage. However, research on biomass yield and quality related to a wide range of harvest timing from multiple environments and years is lacking. Our objective was to determine the effect of harvest timing on yield, moisture, and mineral concentration of switchgrass (Panicum virgatum L.) and native polyculture biomass. Biomass was harvested on 56 unique days ranging from late summer (2 September) to late spring (20 May) spanning 3 years (2009 to 2011) and seven sites in Minnesota, USA. Biomass yield varied considerably by location and year (range = 0.7–11.7 Mg ha−1) and was lowest during the winter. On average, there was no difference in biomass yield harvested in early fall compared to late spring. Biomass moisture content was lowest in late spring, averaging 156 g kg−1 across all locations and years when harvested after 1 April. Biomass N concentration did not change across harvest dates; however, P and K concentrations declined dramatically from late summer to late spring. Considering the economic costs of replacing exported minerals and changes in revenues from biomass yield through time, biomass harvest should be conducted in late summer–early fall or late spring and avoided in winter. However, biomass managed for gasification should be harvested in spring to reduce concentrations of minerals that lead to slagging and fouling. Changes in biomass yield and quality through time were similar for switchgrass and native polyculture biomass. These biomass harvest recommendations are made from data spanning multiple years and locations and should be applicable to various growing conditions across the Upper Midwest.

In May 2010, alley cropping systems consisting of switchgrass (Panicum virgatum L.), prairie cordgrass (Spartina pectinata Bosc ex Link), an alfalfa (Medicago sativa L.) and intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth and Dewey) mixture, and a native tallgrass-forb-legume polyculture, planted between multi-row strips of poplar hybrid ‘NM6’ (Populus maximowiczii x P. nigra) and willow cultivar ‘Fish Creek’ (Salix purpurea) were established at Empire and Granada, Minnesota, USA. Crop establishment and productivity were characterized for each species over two growing seasons and at two distances from the tree-crop interface. Prairie cordgrass and the native polyculture were among the most productive herbaceous crops at both sites, averaging between 7.1 and 11.9 Mg DM ha−1, and have shown no evidence of competition for resources along the tree-crop interface thus far. Basal area (BA) was similar at Empire for NM6 (1,744 mm2 tree−1) and Fish Creek (1,609 mm2 tree−1), but was greater for NM6 (1,045 mm2 tree−1) than Fish Creek (770 mm2 tree−1) at Granada. Despite this, stand basal area (SBA) was greater for Fish Creek at both sites due to greater planting density. Across species, BA and SBA were greater for trees along the alley than those in center rows at Empire, whereas no difference was observed at Granada. Results suggest that alley cropping provides suitable conditions for establishment of short-rotation woody and certain herbaceous biomass crops, and that some of these crops may be well suited to the alley cropping environment. However, continued research is needed to evaluate crop persistence and productivity as crops and trees mature and the potential for interspecies competition increases.

The use of perennial biomass crops is expected to increase and will likely be part of a diversified approach to cropping system design that focuses on multiple economic, ecological, and environmental benefits. Field experiments were conducted from 2006 to 2011 at three locations in Minnesota to quantify biomass production across a diverse set of perennial herbaceous and woody crops. Herbaceous crops were harvested annually in the fall while the woody crops were harvested once following five years of growth. Willow produced more total biomass than all other woody and herbaceous biomass crops across all locations. However, miscanthus biomass yield was similar to ‘SX67’ willow at St. Paul and Waseca, but was dependent on the cultivar of miscanthus. Prairie cordgrass cultivars were among the highest and most consistent yielding herbaceous biomass crops across locations. Miscanthus cultivars produced the highest annual dry matter yield of 35 Mg ha−1 yr−1 biomass, but only during the final year of the study. Other herbaceous crops such as switchgrass performed well in certain locations and may offer flexibility in cropping choice. This unique information on comparative biomass yield across a diversity of perennial crops will inform the overall decision-making process in a way that reduces risk and optimizes productivity in specific environments. This study shows that several biomass crop species can be successfully grown as part of a diversified biomass cropping enterprise.

Objective: Plants respond to their environment in a multitude of ways. Gradual movements occur in response to light (phototropism), and more rapid movements occur in response to touch (thigmatropism). In this report, we describe a rapid movement response that occurs in plants without any physical contact with the seedlings that is based on electric charge. Methods: Three varieties of seeds were planted in the laboratory under sterile conditions. After 5-10 days the seedlings were tested for their response to electric field stimuli, and video responses were recorded. Results: Plant seedlings of Thymus vulgaris, Arabidopsis thaliana and Mentha spicata, starting at the 2 or 3 leaf stage, were capable of msec movement responses to objects that conveyed an electric charge. The fluctuation in the electric field was measured with a sensor attached to an oscilloscope. The addition of a known ion channel blocker, amiloride hydrochloride, to the nutrient media inhibited the plant response in two species tested, Mentha spicata and Arabidopsis thaliana. Conclusion: This evidence suggests that a possible mechanism for the rapid movement operates through the closure of ion channels similar to the rapid closure of the Venus flytrap.

Diversification of agroecological systems to enhance agrobiodiversity is likely to be critical to advancing environmental, economic, and social sustainability of agriculture. Temperate-zone agroecological systems that are currently organized for production of summer-annual crops can be diversified by integration of fallow-season and perennial crops. Integration of such crops can improve sustainability of these agroecological systems, with minimal interference with current agricultural production. Importantly, these crops can provide feedstocks for a wide range of new bio-products that are forming a new agricultural bioeconomy, potentially providing greatly increased economic incentives for diversification. However, while there are many fallow-season and perennial crops that might be used in such a “bioeconomic” strategy for diversification, most are not yet well adapted and highly-marketable. Efforts are underway to enhance adaptation and marketability of many such crops. Critically, these efforts require a strategic approach that addresses the inherent complexity of these projects. We outline a suitable approach, which we term “sustainable commercialization”: a coordinated innovation process that integrates a new crop into the agriculture of a region, while intentionally addressing economic, environmental and social sustainability challenges via multi-stakeholder governance. This approach centers on a concerted effort to coordinate and govern innovation in three critical areas: germplasm development, multifunctional agroecosystem design and management, and development of end uses, supply chains, and markets. To exemplify the approach, we describe an ongoing effort to commercialize a new fallow-season crop, field pennycress (Thlaspi arvense L.).

There are significant concerns over the long- and short-term implications of continuous glyphosate use and potential problems associated with weed species shifts and the development of glyphosate-resistant weed species. Field research was conducted to determine the effect of herbicide treatment and application timing on weed control in glyphosate-resistant soybean. Ten herbicide treatments were evaluated that represented a range of PPI, PRE, and POST-only application timings. All herbicide treatments included a reduced rate of glyphosate applied POST. PRE herbicides with residual properties followed by (fb) glyphosate POST provides more effective control of broadleaf weed species than POST-only treatments. There was no difference in soybean yield between PRE fb POST and POST-only treatments in 2008. Conversely, PRE fb POST herbicide treatments resulted in greater yield than POST-only treatments in 2009. Using PRE fb POST herbicide tactics improves weed control and reduces the risk for crop yield loss when dealing with both early- and late-emerging annual broadleaf weed species across variable cropping environments.

Potential crop yield loss due to early-season weed competition is an important risk associated with postemergence weed management programs. WeedSOFT is a weed management decision support system that has the potential to greatly reduce such risk. Previous research has shown that weed emergence time can greatly affect the accuracy of corn yield loss predictions by WeedSOFT, but our understanding of its predictive accuracy for soybean yield loss as affected by weed emergence time is limited. We conducted experiments at several sites across the Midwestern United States to assess accuracy of WeedSOFT predictions of soybean yield loss associated with mixed-species weed communities established at emergence (VE), cotyledon (VC), first-node (V1), or third-node (V3) soybean. Weed communities across research sites consisted mostly of annual grass species and moderately competitive annual broadleaf species. Soybean yield loss occurred in seven of nine site-years for weed communities established at VE soybean, four site-years for weed communities established at VC soybean, and one site-year for weed communities established at V1 soybean. No soybean yield loss was associated with weed communities established at the V3 stage. Nonlinear regression analyses of predicted and observed soybean yield data pooled over site-years showed that predicted yields were less than observed yields at all soybean growth stages, indicating overestimation of soybean yield loss. Pearson correlation analyses indicated that yield loss functions overestimated the competitive ability of high densities of giant and yellow foxtail with soybean, indicating that adjustments to competitive index values or yield loss function parameters for these species may improve soybean yield loss prediction accuracy and increase the usefulness of WeedSOFT as a weed management decision support system.

Do divisive primaries hurt incumbents? If so, does the electoral calendar condition their effects? Potential challengers are predatory and estimate their electoral chances before running against an incumbent, meaning electoral prospects influence both primary divisiveness and general election performance. However, divisive primaries may waste precious campaign resources and damage the primary winner’s reputation. The evidence suggests that although divisive primaries generally hurt incumbents and help challengers as electoral prospects theory predicts, these effects wane and eventually disappear the closer the primary is to the general election.

Motivated by theories of congressional committees in the US context, and building on the growing body of work focusing on the institutional features of legislatures in Latin American presidential systems, this paper explores two previously overlooked aspects of committee politics. Using comparative data from three Latin American countries, it examines the strategic and jurisdictional dynamics in which chamber leaders assign bills to committees and then investigate the factors affecting presidential and partisan success within committees. In general, the authors find that committees have strong property rights and that characteristics of both bills and bill initiators strongly influence the survival of legislation in committee. The results shed light on the effects of institutional design on the policy process in presidential systems.

Integrating annual and perennial crops at the field scale creates new opportunities for increasing financial return while addressing important environmental and ecological issues. An understanding of biomass productivity on specific landscape positions is essential to realizing this goal. The objective of this research was to determine the effect of landscape position on the productivity of herbaceous and woody biomass crops. Alfalfa (Medicago sativa L.), corn (Zea mays L.), willow (Salix spp.), cottonwood (Populus deltoides W. Bartram ex Marshall), poplar (Populus maximowiczii x P. nigra), and switchgrass (Panicum virgatum) were planted on seven landscape positions. Soil attributes were measured and included soil nitrogen, P, K, and profile darkness index (PDI). Terrain attributes included specific catchment area (SpecCat) and compound terrain index (CTI). A hierarchical Bayesian approach was used to analyze spatial data. Corn grain and stover yield was lowest in depositional and flat areas that retain water for longer periods of time and highest on well drained summit positions. Corn stover yield was positively correlated to nitrogen, PDI, SpecCat, and CTI, whereas corn grain yield was not correlated to any of the soil or terrain attributes tested. Conversely, willow productivity was among the highest at the depositional position and lowest at the summit position. For SX67 willow, growth was positively correlated to SpecCat, whereas 9882 willow growth was negatively correlated to PDI and CTI. Alfalfa and poplar productivity was highest at a site characterized by a relatively steep slope with potentially erosive soils.

Why do voters reward or punish the incumbent government? A number of studies show that economic performance often drives support, though the strength of this relationship is often conditional. This article suggests that economic voting may also be conditioned by the breaking and keeping of campaign promises. A number of presidents throughout Latin America have campaigned explicitly against neoliberal economic policies, only to pursue them aggressively once in office. This study argues that presidents who abandon their promises assert the executive's responsibility for the economy and raise the salience of economic issues in the next election. Consequently, voters respond rationally to these policy switches, rewarding them when they succeed and punishing them when they fail. Using data from 78 presidential elections across 18 countries, this study finds substantial evidence that broken promises exacerbate the consequences of poor economic performance and magnify the benefits of good economic performance.

WeedSOFT is a state-of-the-art decision support system for weed management in the north central region of the United States, but its accuracy to predict corn yield loss associated with later-emerging weed communities has not been adequately assessed. We conducted experiments in 2004 and 2005 to compare observed and predicted corn yield related to four establishment times of mixed-species weed communities for validation of competitive index modifier (CIM) values in WeedSOFT. Weed communities were established at VE, V2, V4, and V6 corn (emergence, second-leaf, fourth-leaf, and sixth-leaf stages, respectively), and consisted largely of annual grass and moderately competitive annual broadleaf species. Compared to weed-free corn, yield loss occurred in each of seven site-years for weed communities established at VE corn, but in only one site-year for communities established at V2 corn. No corn yield loss was associated with weed communities established at V4 or V6 corn. For communities established at VE corn, predicted corn yield differed from observed yield in all but one site year, with predicted yield less than observed yield in three site-years, and greater than observed yield in two site-years; however, nonlinear regression analyses of yield data pooled over site-years showed that fitted values were similar between predicted and observed yield. For communities established at V2 and V4 corn, predicted yield was less than observed yield in six and five site-years, respectively. For communities established at V6 corn, predicted yield was less than observed yield in three of six site-years, but was similar to observed yield in three of six site-years. These results indicated that the CIM values in WeedSOFT tended to overestimate the competitiveness of late-emerging weed communities. Corn yield data from a pooled analysis of all site-years were used to generate a revised set of growth stage CIM values, which improved the accuracy of predicted corn yield. These results should improve weed management decisions and reduce the need for herbicide applications to late-emerging weeds.

Alfalfa (Medicago sativa L.) is a promising bioenergy and bioproduct feedstock because of its high yield, N-fixation capacity, potential for planting in rotation with corn (Zea mays L.), and valuable protein co-product (leaf meal). Our objective was to examine the effect of growth environment on biomass yield, cellulosic ethanol traits, and paper pulp fiber characteristics of alfalfa stems. Landscape position (summit and mild slope), season of harvest (four harvests per season), and multiple years (2005 and 2006) provided environmental variation. Alfalfa stem samples were analyzed for cell wall carbohydrate and lignin concentration. Stems were subjected to dilute acid pre-treatment, enzymatic saccharification, and pulping processes to measure relevant cellulosic ethanol and paper production traits. Landscape position was not a significant source of variation for yield or any biomass quality trait. Yields varied among harvests in 2005 (1,410–3,265 kg ha−1) and 2006 (1,610–3,795 kg ha−1). All cell wall, conversion test, and paper production traits exhibited year by harvest interactions with no clear pattern. Total carbohydrates and lignin ranged from 440 to 531 g kg−1 DM and from 113 to 161 g kg-1 DM, respectively. Release of cell wall sugars by the conversion test ranged widely (419 to 962 g kg−1 DM). Fiber traits were similarly variable with length and fine content ranging from 1.24 to 1.59 mm and from 15.2% to 21.9%, respectively. Utilizing alfalfa biomass for cellulosic ethanol and paper pulp production will involve dealing with significant feedstock quality variation due to growth environment.