Sweet sorghum [SS; Sorghum bicolor (L.) Moench] is a potential biofuel crop for the Great Plains. Sweet sorghum was compared with corn [Zea mays (L.)] and grain sorghum for potential ethanol yield, energy use efficiency, and greenhouse gas (GHG) emissions at seven dryland site‐years in Nebraska. Seasonal rainfall ranged from approximately 340 to 660 mm. Soils were deep with medium texture at all site‐years. The effects of seeding rate, N rate, and cultivar on SS performance were evaluated. Sweet sorghum sugar yield was not affected by seeding rate and N application at six of seven site‐years, but yield was increased by 19% at one site‐year. Calculated ethanol yield and net energy yield were 33 and 21% more, respectively, with the grain crops compared with SS, but mean net energy yield of an earlier‐maturing SS cultivar was comparable with the grain crops. The mean ratio of energy produced in ethanol per total energy invested was 23% less for grain crops compared with SS. Mean life cycle GHG emissions were 53% and 66 to 69% less compared with gasoline for SS and grain crops, respectively. Very efficient use of the ethanol coproducts was assumed for the grain crops while SS bagasse was assumed to be returned to the field. At least one SS cultivar is competitive with grain crops for some biofuel criteria, but SS is not competitive with grain crops for total or net liquid transportation fuel produced per hectare.

Herbicide‐resistant crops like glyphosate resistant (GR) soybean [Glycine max (L.) Merr.] are gaining acceptance in U.S. cropping systems. Comparisons from cultivar performance trials suggest a yield suppression may exist with GR soybean. Yield suppressions may result from either cultivar genetic differentials, the GR gene/gene insertion process, or glyphosate. Grain yield of GR is probably not affected by glyphosate. Yield suppression due to the GR gene or its insertion process (GR effect) has not been reported. We conducted a field experiment at four Nebraska locations in 2 yr to evaluate the GR effect on soybean yield. Five backcross‐derived pairs of GR and non‐GR soybean sister lines were compared along with three high‐yield, nonherbicide‐resistant cultivars and five other herbicide‐resistant cultivars. Glyphosate resistant sister lines yielded 5% (200 kg ha−1) less than the non‐GR sisters (GR effect). Seed weight of the non‐GR sisters was greater than that of the GR sisters (in 1999) and the non‐GR sister lines were 20 mm shorter than the GR sisters. Other variables monitored were similar between the two cultivar groups. The high‐yield, nonherbicide‐resistant cultivars included for comparison yielded 5% more than the non‐GR sisters and 10% more than the GR sisters.

In 2017, dicamba-resistant (DR) soybean was commercially available to farmers in the United States. In August and September of 2017, a survey of 312 farmers from 60 Nebraska soybean-producing counties was conducted during extension field days or online. The objective of this survey was to understand farmers’ adoption and perceptions regarding DR soybean technology in Nebraska. The survey contained 16 questions and was divided in three parts: (1) demographics, (2) dicamba application in DR soybean, and (3) dicamba off-target injury to sensitive soybean cultivars. According to the results, 20% of soybean hectares represented by the survey were planted to DR soybean in 2017, and this number would probably double in 2018. Sixty-five percent of survey respondents own a sprayer and apply their own herbicide programs. More than 90% of respondents who adopted DR soybean technology reported significant improvement in weed control. Nearly 60% of respondents used dicamba alone or glyphosate plus dicamba for POST weed control in DR soybean; the remaining 40% added an additional herbicide with an alternative site of action (SOA) to the POST application. All survey respondents used one of the approved dicamba formulations for application in DR soybean. Survey results indicated that late POST dicamba applications (after late June) were more likely to result in injury to non-DR soybean compared to early POST applications (e.g., May and early June) in 2017. According to respondents, off-target dicamba movement resulted both from applications in DR soybean and dicamba-based herbicides applied in corn. Although 51% of respondents noted dicamba injury on non-DR soybean, 7% of those who noted injury filed an official complaint with the Nebraska Department of Agriculture. Although DR soybean technology allowed farmers to achieve better weed control during 2017 than previous growing seasons, it is apparent that off-target movement and resistance management must be addressed to maintain the viability and effectiveness of the technology in the future.

Glyphosate (N-(phosphonomethyl) glycine)-resistant (GR) soy- Missouri, personal communication, 1999). bean [Glycine max (L.) Merr.] technology is gaining acceptance in U.S. cropping systems, yet potential yield suppression from eitherYield suppression may result from either (i) cultivar cultivar genetic differentials, the GR gene/gene insertion process, or genetic differentials, (ii) the GR gene/gene insertion glyphosate is a concern. Other work shows that the GR gene/gene process (GR effect), or (iii) glyphosate (herbicide efinsertion process may suppress soybean yield. No one has reported fect), or a combination of the three. Thus, in the first the effects of glyphosate on a diverse group of commercially available situation yield of GR cultivars may be suppressed rela-GR soybean cultivars. In this study we evaluated one of the potential tive to that of other cultivars simply because the GR sources of GR yield suppression-the effect of glyphosate on yield, gene was inserted in low yielding or older cultivars. We growth, and development of GR cultivars. Field experiments were consider yield suppression associated with the GR effect conducted at four Nebraska locations with12 GR cultivars in 1998 and or herbicide effect a greater potential problem than 13 GR cultivars in 1999. Soybean response to glyphosate, ammonium cultivar genetic differentials since the latter can be oversulfate (AMS), and water application at 21 and 42 d after soybean emergence was compared with control plots treated with AMS and come by inserting the GR gene in high yielding parent water in 1998. An additional control, water alone, was added in 1999.

Pollinators serve critical roles for the functioning of terrestrial ecosystems, and have an estimated annual value of over $150 billion for global agriculture. Mounting evidence from agricultural systems reveals that pollinators are declining in many regions of the world, and with a lack of information on whether pollinator communities in natural systems are following similar trends, identifying factors which support pollinator visitation and services are important for ameliorating the effects of the current global pollinator crisis. We investigated how fire affects resource structure and how that variation influences floral pollinator communities by comparing burn versus control treatments in a southeastern USA old-field system. We hypothesized and found a positive relationship between fire and plant density of a native forb, Verbesina alternifolia, as well as a significant difference in floral visitation of V. alternifolia between burn and control treatments. V. alternifolia density was 44% greater and floral visitation was 54% greater in burned treatments relative to control sites. When the density of V. alternifolia was experimentally reduced in the burn sites to equivalent densities observed in control sites, floral visitation in burned sites declined to rates found in control sites. Our results indicate that plant density is a proximal mechanism by which an imposed fire regime can indirectly impact floral visitation, suggesting its usefulness as a tool for management of pollination services. Although concerns surround the negative impacts of management, indirect positive effects may provide an important direction to explore for managing future ecological and conservation issues. Studies examining the interaction among resource concentration, plant apparency, and how fire affects the evolutionary consequences of altered patterns of floral visitation are overdue.