Summer Annual Crops Research Articles

Emergence modeling of three‐lobe morning glory (Ipomoea triloba L.) and demographic parameters of seed longevity and persistence in the soil

AbstractThree‐lobe morning glory (Ipomoea triloba L.) is an annual weed, which presents vigorous growth, long cycle, and tolerance to glyphosate. Thus, knowledge of aspects related to germination and behavior in the seed bank of this species are essential for the adoption of appropriate management practices to reduce the population in agricultural fields. Therefore, the objective of this work was to characterize the requirements for three‐lobe morning glory germination, perform field emergence modeling using thermal and hydrothermal time models, and determine the longevity of the seed bank. Eight temperatures and 10 water potentials were tested in the laboratory to determine the base temperature and water potential for seed germination. For the modeling of the emergence, field experiments were conducted between the years 2014 and 2018 considering three sampling times (10/20, 11/10, and 12/01), which coincide with the sowing times of summer annual crops. To evaluate the longevity and persistence of the seed bank, a factorial experiment was conducted in which factor A consisted of three burial depths and factor B consisted of five harvesting times. Base values for three‐lobe morning glory emergence are base, optimum, and maximum temperatures of 12.32, 29.82, and 43.31°C, respectively, and base water potential of −0.80 MPa. Both models are adequate to predict the emergence of three‐lobe morning glory in the three sampling times. The species has a persistent seed bank, in which the greater the depth of seed burial, the greater the longevity of the seed bank, and can remain viable for up to 16 months.

Drivers of species composition in arable‐weed communities of the Austrian–Hungarian borderland region: What is the role of the country?

AbstractQuestionsDue to their high ecological and agronomical variability, borderland regions offer an excellent opportunity to study assembly patterns. In this study we compared the influence of various factors on summer annual weed communities consisting of both native and introduced species.LocationThe borderland region of Austria and Hungary.MethodsWe assessed the abundance of weed species in 300 fields of six summer annual crops, and collected information on 26 background variables for each plot. We applied redundancy analysis (RDA) to estimate multivariate species responses and variation partitioning to compare the relative importance of three groups of variables (environmental variables, management variables, and country as a singleton group), and we also checked for statistical association between country and the predictors of the other two groups.ResultsThe full RDA model explained 22.02% of the variance in weed species composition. Variation partitioning showed that environment and management had similarly high (~8%) influence on weeds, while country had a modest yet substantial (~1%) effect, and there was relatively little overlap between the variance attributable to the three groups. Comparing the individual variables, country ranked third (after preceding crop, and actual crop). The effects of 15 further variables were also significant, including seven management, and seven environmental variables, as well as the location of the sampling plots within the fields. Comparisons between the countries showed that farming type, preceding crops, tillage system, tillage depth and field size were significantly different between the countries.ConclusionsCountry exhibited a small but significant influence on weed community composition, which could not be explained with easily accessible management and environmental variables. This suggests that the distinct historical agronomical background of the two countries, possibly involving some legacies of the former Iron Curtain period, still has an impact on the weed species composition of arable fields.

Impacts of fallow cropland winter “weeds” on honey bee pre-swarm colony growth

Lack of adequate floral resources is a key driver of bee population declines and honey bee colony loss, particularly in agricultural landscapes. Most studies evaluating floral resource use and land management consequences in honey bees focus on the period after new colony founding from reproductive swarms (spring-fall). Few studies have investigated nutrition in the late-winter/early-spring (LWES) period, the critical time when colonies break their winter dormancy and increase their colony populations in preparation for swarming. Growth during this timeframe influences beekeepers’ ability to produce new colonies and predicts colony productivity for the remainder of the active season. In agricultural areas growing summer annual crops, many fields are fallow during LWES and anecdotally grow large quantities of early blooming winter annual herbaceous “weeds”. The value of these resources to honey bee colony health is unknown. In this study, conducted in central Kentucky, we characterized blooming winter annual plant abundance across different land cover types. We placed colonies on sites with varying quantities of blooming winter annual plants and assessed colony growth and individual worker immune system function over LWES. We found that blooming winter annual plants are most abundant on croplands and limited on forested sites and sites dominated by grasses (including lawns and pastures). Colonies on sites with the lowest quantities of blooming winter annual plants showed reduced LWES growth and patterns of individual worker gene expression consistent with nutritional stress relative to colonies on sites with greater abundances of blooming winter annuals. We used the National Land Cover Database to show that proximity to crop fields at larger spatial scales also had positive impacts on colony growth during LWES. Taken together, these results suggest blooming winter annual plants, and, more generally, croplands, may provide critical floral resources for honey bees during the critical pre-swarm growth period following winter dormancy.

Harvest aids did not advance maturity of non‐shatter pennycress

AbstractReliance on summer annual crops in the Upper Midwest results in fallow land from late fall through early spring, providing opportunities to integrate winter crops, such as pennycress (Thlapsi arvense L.), onto the landscape. Pennycress agronomics have primarily been studied using unimproved wild‐type lines prone to seed shatter, resulting in significant yield loss if not harvested early. However, high plant and seed moisture complicates harvest and seed storage. A new breeding line with a reduced‐shatter mutation made it possible to use harvest aids to reduce plant moisture without the risk of seed loss. The objectives of this study were to quantify the reduction in pennycress seed and biomass moisture after applying a harvest aid and to assess the seed yield, oil content, and crude protein of the reduced‐shatter line. This study was conducted over the 2018–2019 and 2019–2020 growing seasons with ‘“IO217” pennycress in Rosemount, MN. Seed moisture decreased to a similar level by harvest maturity regardless of treatment while swathing was the most effective method of reducing biomass moisture. Natural senescence decreased pennycress moisture content to a harvestable level at the same rate as treated plants, indicating that a harvest aid is not required at this time. Seed yield was two to six times higher than in studies using unimproved pennycress lines. Challenges associated with wild‐type pennycress lines, such as uneven germination and late maturation, were prevalent in this study and further genetic improvement will be necessary to ensure successful pennycress production in the Upper Midwest.

Soybean Cyst Nematode Population Development and its Effect on Pennycress in a Greenhouse Study.

Midwest crop production is dominated by two summer annual crops grown in rotation, viz., corn (Zea mays L.) and soybean (Glycine max L.). Winter oilseed crops, such as pennycress (Thlaspi arvense L.), can provide ecosystem and economic benefits when added to the corn–soybean rotation. However, adding a new crop adds risks, such as increased pest pressure. The objectives of this study were to (i) evaluate population development of three soybean cyst nematode (SCN; Heterodera glycines) biotypes on three pennycress genotypes and susceptible soybean and (ii) determine whether SCN inoculation level influenced plant biomass. SCN population density and biomass were determined after 60 d in the greenhouse. At the inoculation level of 2,000 eggs/100 cm3 soil, the average egg density for the three pennycress genotypes was 1,959 eggs/100 cm3 soil, lower than that for the susceptible soybean ‘Sturdy’ (9,601 eggs/100 cm3 soil). At the inoculation level of 20,000 eggs/100 cm3 soil, the average egg density for the three pennycress genotypes was 6,668 eggs/100 cm3 soil, lower than that for ‘Sturdy’ (40,740 eggs/100 cm3 soil). The inoculation level did not affect plant biomass. Pennycress is an alternative host to SCN under greenhouse conditions but is a less suitable host than soybean.

Adapting the CROPGRO model to simulate growth and production of Brassica carinata, a bio‐fuel crop

AbstractCarinata (Brassica carinata) is an oilseed crop which, because of its non‐edible oil composition and favorable fatty acid profile, is proposed as a “green” sustainable aviation fuel. It can be grown as a winter crop in the southeastern USA or as a summer annual crop in northern latitudes. No crop models exist for carinata because it is a relatively new crop. The CROPGRO model is a mechanistic crop simulation of daily crop growth and development as a function of daily weather, soil properties, crop management, and species parameters. We adapted the CROPGRO model to simulate carinata based on growth analysis data collected over two seasons at three sites: Quincy, FL, Jay, FL, and Shorter, AL. The adaptation process required literature knowledge as well as optimization against field observations. The parameterization of model sensitivities to climatic factors is presented. The adapted model gave good simulations of carinata growth dynamics compared to observed growth during different seasons and locations and in response to N fertilization. While additional testing is appropriate, the model is sufficiently ready to be used for various applications. An example application is presented for the effect of sowing date on carinata yield and maturity over long‐term weather in the Southeastern USA.

PSVI-22 Rumen microbiome of beef cattle is modulated by backgrounding systems

Abstract Backgrounding (BKG) segment in beef production systems is characterized by utilization of different forages which affect growth performance and carcass characteristics. However, it is unclear how BKG systems impact rumen microbiome. We investigated rumen microbiome dynamics of beef calves under different BKG systems. At weaning, Angus and Angus x Simmental beef calves (n = 38) were stratified by age, weight, and sex in a completely randomized design into 1 of 3 BKG treatments for 55 d: 1) perennial pasture (PP; quackgrass, orchardgrass; smooth bromegrass, red clover, and alfalfa); 2) summer annual cover crop (CC; cereal oats, purple top turnips, hunter forage brassica, and graza forage radish); and 3) dry lot (DL; haylage, corn, and DDGS). After BKG, all calves were assigned to a high energy ration in a feedlot. Rumen sample was collected via esophageal tubing at weaning, BKG and feedlot. A total of 190 rumen fluid samples were used to sequence the hypervariable V4 region of the 16S rRNA bacterial gene on an Illumina MiSeq platform. The results showed that BKG systems largely influenced rumen bacterial communities. Specifically, microbiome composition and diversity were not different at weaning, diverged significantly during BKG (Shannon index, Bray Curtis distance metrics; P < 0.001) and homogenized during feedlot. During the BKG segment, the bacterial genera Agrobacterium, Coprococcus, and Ruminococcus were dominant in CC whereas Fibrobacteraceae and Mycoplasmataceae was most dominant in DL. Moreover, rumen microbiome patterns of CC and DL calves showed increased plasticity in early stages of development but not during feedlot with PP showing fewer changes over time. These results indicate that BKG systems significantly modulate the rumen microbiome of beef cattle and, underscore the importance of early developmental stages as potential targets for feeding interventions that can impact the animal microbiome to enhance animal performance.

Efficacy of Different Herbicides on Echinochloa colona (L.) Link Control and the First Case of Its Glyphosate Resistance in Greece

E. colona is a C4 annual summer grass which is troublesome to major summer annual and perennial crops. Due to recent complaints by the farmers, the objectives of the present study were to evaluate the efficacy of penoxsulam, profoxydim, cycloxydim, cyhalofop-butyl, florpyrauxifen-benzyl and glyphosate against six E. colona accessions, and also to evaluate the response of these accessions to different rates of glyphosate in a dose-response experiment. In the first experiment, herbicides were applied at their maximum recommended label rates, while in the dose-response experiment, glyphosate was applied at six doses corresponding to 0, 1/4X, 1/2X, X, 2X, and 4X of the recommended rate. The dry weight of the biotypes TH8 and TH7 treated with profoxydim was 66% and 68% of the untreated control, respectively. The efficacy of cyhalofop-butyl against three accessions was lower than 30%, while two accessions were susceptible to this herbicide. The efficacy of penoxsulam against the biotypes ET2 and ET4 was lower than 10%, while dry weight of FT5 and TH8 was only reduced by 23%–28% as compared to the control. Cycloxydim application provided control higher than 75% at 21 days after treatment (DAT) of three accessions, while the majority of E. colona accessions was adequately controlled by the application of florpyrauxifen-benzyl. The response of the different accessions to glyphosate varied. The results of the glyphosate dose-response experiment revealed that the GR50 values of the resistant E. colona accessions ET2 and ET4 were up to 1098 and 1220 g a.e. ha−1 of glyphosate, respectively, whereas the GR50 value of the susceptible accession (FT5) was only 98 g a.e. ha−1. The resistance indices of ET2 and ET4 were 12.4 and 11.2, respectively, indicating that they have already developed resistance to glyphosate. Three more accessions could be also of developing resistant to glyphosate. This is the first report of glyphosate resistance from E. colona accessions in Greece, with indications of multiple resistance also present. Further research is needed in order to evaluate the efficacy of several herbicides under different soil and climatic conditions, conduct baseline sensitivity studies, reveal the evolvement of resistance patterns to glyphosate from accessions of Echinochloa spp., and search for alternative options of weed management in annual and perennial crops due to the clear indications of multiple resistance situations.

Yield tradeoffs and weed suppression in a winter annual oilseed relay‐cropping system

AbstractMidwest crop production is dominated by two summer annual crops grown in rotation, corn (Zea mays L.) and soybean (Glycine max [L.] Merr.). This rotation leaves a productivity gap during the spring and autumn. Winter oilseed crops, such as pennycress (Thlaspi arvense L.), and winter camelina (Camelina sativa [L.] Crantz), can fill this gap and provide ecosystem and economic benefits. The objectives of this study were to: (i) examine the tradeoffs between soybean and winter oilseed yields in the relay‐cropping system, (ii) determine legacy effects on corn 1 yr after oilseed–soybean relay‐cropping, and (iii) evaluate the weed suppression abilities of the winter oilseeds. Three sites were used across Minnesota to evaluate winter oilseeds and commodity crop yields in a relay‐cropping production system. Total seed production of the system (winter oilseed crop + soybean) was increased by 20% at one site, whereas at the other two sites, total yields were similar when compared to mono‐cropped soybean. Soybean yield was reduced at two of the three sites by 20 and 47% by the inclusion of winter oilseeds. Soybean yield was unaffected by inclusion of winter oilseeds at the third site. In the subsequent year, corn yield was unaffected by the winter oilseed treatments. Weeds were suppressed by the winter oilseeds crops. Pennycress reduced weed biomass by 97% to 100%, and camelina treatment reduced weed biomass by 85% to 87%. The inclusion of winter oilseeds in the corn–soybean cropping system can increase overall seed production and suppress early season weeds.

An Economic Analysis of Cluster Bean Production in Bikaner District of Rajasthan

Cluster Bean (Cyamopsis tetragonoloba L. Taub) commonly known as is a drought and high temperature tolerant Cyamopsis tetragonoloba Guar, deep-rooted summer annual legume crop cultivated mainly in the Kharif season in an arid region and used as animal feed, fodder, green manure and extraction of gum for industrial uses. India is the largest producer of cluster bean and contributes 80 percent of total cluster bean production in the world. Rajasthan is the single largest producer and alone contributed to more than 70 percent of India’s total output. The increased demand for guar gum resulted in a strong escalation of the prices of cluster bean. Looking at the agricultural and industrial importance of this marginalized crop in Rajasthan, particularly realizing the potential in Bikaner district of the state, the present study attempted to analyze the present scenario of the production of cluster bean crops in Bikaner district of the state. A return per rupee invested in cluster bean crop was higher in the small farm (1:1.38) and marginally lowers on the medium farm (1:1.35). Break-even guar production ranged between 4.26 to 5.19 q per ha in small farm, 4.16 to 4.99 q per ha in medium and 3.98 to 4.94 q per ha on a large farm.

Cover crop residue components and their effect on summer annual weed suppression in corn and soybean

AbstractCover crop residue can act as a mulch that will suppress weeds, but as the residue degrades, weed suppression diminishes. Biomass of cover crop residue is positively correlated to weed suppression, but little research is available regarding the composition of cover crop residue and its effect on weed suppression. Field experiments were conducted to determine the impact of cover crop residue properties (i.e., total carbon, total nitrogen, lignin, cellulose, and hemicellulose) on summer annual weed suppression and cash crop yield. Cover crop monocultures and mixtures were planted in the fall and designed to provide a range of biomass and residue properties. Cover crops were followed by corn (Zea mays L.) or soybean [Glycine max (L.) Merr.]. At termination, cover crop biomass and residue components were determined. Biomass ranged from 3,640 to 8,750 kg ha−1, and the carbon-to-nitrogen (C:N) ratio ranged from 12:1 to 36:1. As both cover crop biomass and C:N ratio increased, weed suppression and duration of suppression increased. For example, a C:N ratio of 9:1 is needed to suppress redroot pigweed (Amaranthus retroflexus L.) 50% at 4 wk after termination (WAT), and that increases to 16:1 and 20:1 to have 50% suppression at 6 and 8 WAT, respectively. Similarly, with biomass, 2,800 kg ha−1 is needed for 50% A. retroflexus suppression at 4 WAT, which increases to 5,280 kg ha−1 and 6,610 kg ha−1 needed for 50% suppression at 6 and 8 WAT, respectively. In general, similar trends were observed for pitted morningglory (Ipomoea lacunosa L.) and large crabgrass [Digitaria sanguinalis (L.) Scop.]. Corn and soybean yield increased as both cover crop biomass and C:N ratio increased where no weed control measures were implemented beyond cover crop. The same trend was observed with cash crop yield in the weed-free subblocks, with one exception. This research indicates that cover crop residue composition is important for weed control in addition to biomass.

The Combined Influence of Cover Crops and Manure on Maize and Soybean Yield in a Kentucky Silt Loam Soil

Management that degrades soil can be one of the main causes of low agricultural productivity and environmental problems in many agricultural regions. There is renewed interest in soil conservation practices to promote sustainable agriculture by improving soil quality and productivity. In this study, the short-term on-farm benefits of cover crops and manure on crop yield and biomass were examined during two consecutive growing seasons. The experiment was conducted at a small-producer farm in Logan County, Kentucky, USA. Soybean (Glycine max L.) and maize (Zea mays L.) were used as summer annual rotation crops in no-tilled soils. A cover crop mix of cereal rye (Secale cereale L.), Austrian winter pea (Pisum sativum L.), and crimson clover (Trifolium incarnatum L.) was planted after the main crop was harvested each year. Aboveground biomass of the soybean and maize were assessed, and yield was estimated from hand-harvested plants. In the first year of the study (2016), there were apparent but not significant beneficial effects of animal manure and cover crops on soybean yield, but not on biomass. The biomass and maize grain yield in the second year (2017) were detectable, significant, and increased as a result of the cover crops and manure application (p < 0.05). While beneficial effects of combining cover crops and manure may not be obvious in the first year of a rotation, they can be apparent in subsequent years. However, longer-term observation and measurement are necessary to better quantify the relationship between sustainable conservation practices and productivity.

Short Corn Rotations Do Not Improve Soil Quality, Compared with Corn Monocultures

Compared corn–corn–corn vs. corn–corn–soybean vs. corn–soybean rotations on their effects on soil properties after 12 yr. Locations were correctly identified by canonical discriminant analyses (CDA) rules based on measured soil properties. Regardless of location, soil attributes did not differ under short corn rotations and corn–corn–corn systems. Soil attributes contrasted most between corn and soybean phases of the corn–soybean rotation. Short‐duration summer annual crop rotations are widely used in the Midwest, but their long‐term impact on soil quality has not been thoroughly examined. Our goal was to compare soil properties under long‐term use of the most common crop rotations around Illinois, and to identify soil quality indicators for rotations in the state. Crop rotations of continuous corn (Zea mays L.) (CCC), corn–soybean [Glycine max (L.) Merr.] (CS), and corn–corn–soybean (CCS) were arranged in a randomized complete block design (RCBD), with three or four replications at each of six locations, with all phases present each year for 12 yr. We measured 21 soil properties on the surface soil and 18 properties at four successive depths, rendering a total of 126 and 504 observations available for the multivariate statistical analyses, including principal component analyses (PCA) and canonical discriminant analysis (CDA) in both data sets. We found that our discriminant rules based on the measured soil properties correctly identified the location of origin of the soil samples in 98% of cases, representing <2% error rates for the cross‐validation results at each location. Crop rotations, on the other hand, did not affect any of the soil properties evaluated, results further confirmed by our CDA analyses that showed high error rates for classification. Though these short corn rotations make economic sense, they behave similarly to corn monocultures from the soil quality standpoint, compromising the sustainability of our current agricultural systems and highlighting the need to increase temporal and spatial diversification.

Suppressing Alopecurus myosuroides Huds. in Rotations of Winter-Annual and Spring Crops

Alopecurus myosuroides Huds. has become one of the most abundant grass weeds in Europe. High percentages of winter-annual crops in the rotation, earlier sowing of winter wheat and non-inversion tillage favor A.myosuroides. Additionally, many populations in Europe have developed resistance to acetyl-CoA carboxylase (ACCase), acetolactate synthase (ALS) and photosynthetic (PSII) inhibitors. Hence, yield losses due to A.myosuroides have increased. On-farm studies have been carried out in Southern Germany over five years to investigate abundance, control efficacies and crop yield losses due to A.myosuroides. Three crop rotations were established with varying proportions of winter- and summer-annual crops. The crop rotations had a share of 0, 25 and 50% of summer-annual crops. Within each crop rotation, three herbicide strategies were tested. In contrast to classical herbicidal mixtures and sequences, the aim of one of the herbicide strategies was to keep selection pressure as low as possible by using each mode of action (MOA) only once during the five years. A.myosuroides population was susceptible to all herbicide at the beginning of the experiment. Initial average density was 14 plants m−2. In the rotation with only winter-annual crops, density increased to 5347 ears m−2 in the untreated control plots. Densities were lower in the rotations with 25% and even lower with 50% summer-annual crops. Control efficacies against A. myosuroides in the herbicide strategy using only MOAs of the HRAC-groups B and A, according to the Herbicide Resistance Action Committee (HRAC) classification on MOA, dropped after five years compared to the strategy of changing MOA in every year. Nevertheless, the results demonstrate the need for combining preventive and direct weed-management strategies to suppress A.myosuroides and maintain high weed-control efficacies of the herbicides.

Forage yield, water- and solar radiation-productivities of perennial pastures and annual crops sequences in the south-eastern Pampas of Argentina

Livestock production systems of Argentina show an ongoing process of change in the composition of their forage base, with a gradual increase in the proportion of their area assigned to forage crop sequences (FCS) −in particular that involving successive winter and summer annual forage crops–, at the expense of the area assigned to perennial pastures (PP). However, there are several concerns regarding the efficient use of available environmental resources due to differences in the extent of the establishment periods and due to the occurrence of fallow periods in FCS, as well as regarding the species involved in these systems. Therefore, the main objective of this study was to evaluate the water (WP) and solar radiation productivity (RP) of PP [pure stands of alfalfa (Medicago sativa L.), fertilized and unfertilized stands of tall fescue (Festuca arundinacea Schreb.), and fertilized and unfertilized mixed stands of alfalfa/tall fescue] and FCS [including a summer alternative and oats (Avena sativa L.); the summer alternative was either maize (Zea mays L.) or intercropped maize/soybean (Glycine max L.)] through the analysis of their components, i.e. water (WC) and radiation capture (RC), and their water (WUE) and radiation use efficiency (RUE). Resource capture (WC and RC) was defined as the ratio between captured (evapotranspiration and intercepted solar radiation) and annual available resource (rainfall and incident solar radiation). Resource use efficiency (WUE and RUE) was computed as the dry matter (DM) yield per unit of captured resource. A field experiment was conducted during two consecutive years under rainfed conditions and under non-limiting nitrogen availability in the south-eastern Pampas of Argentina. Perennial pastures were evaluated during both their initial establishment year (Y1) and when already fully established (Y2). Annual-based forage DM yield ranged between 13.0 and 32.4 Mg ha−1 in Y1 and between 5.1 and 23.5 Mg ha−1 in Y2. Differences in resource capture between PP and FCS were directly associated with the crop establishment and fallow periods depending on the nature of the considered resource. The highest WP (2.75–3.64 g DM m−2 mm−1) and RP (0.93–1.42 g DM MJ−1) were reached by FCS, which did not differ (P > 0.05) from that of fully established fertilized PP. Our results demonstrate that resource productivity in FCS is not necessarily higher than for PP, once PP are fully established.

Ecological intensification and arbuscular mycorrhizas: a meta‐analysis of tillage and cover crop effects

Summary Reliance on ecosystem services instead of synthetic, non‐renewable inputs is increasingly seen as key to achieving food security in an environmentally sustainable way. This process, known as ecological intensification, will depend in large part on enhancing below‐ground biological interactions that facilitate resource use efficiency. Arbuscular mycorrhizas (AM), associations formed between the roots of most terrestrial plant species and a specialized group of soil fungi, provide valuable ecosystem services, but the full magnitude of these services may not be fully realized under conventional intensively managed annual agricultural systems. Here, we use meta‐analysis to assess how reducing soil disturbance and periods without roots in agricultural systems affect the formation of AM and the diversity and community composition of arbuscular mycorrhizal fungi (AMF). We compiled data from 54 field studies across five continents that measured effects of tillage and/or cover cropping on AMF colonization and/or communities and assessed effects of management and environmental factors on these responses. Less intensive tillage and winter cover cropping similarly increased AMF colonization of summer annual cash crop roots by ∼30%. The key variables influencing the change in AMF colonization were the type of cover crop or the type of alternative tillage, suggesting that farmers can optimize combinations of tillage and cover crops that most enhance AM formation, particularly with no‐till systems and legume cover crops. Richness of AMF taxa increased by 11% in low‐intensity vs. conventional tillage regimes. Several studies showed changes in diversity and community composition of AMF with cover cropping, but these responses were not consistent. Synthesis and applications. This meta‐analysis indicates that less intensive tillage and cover cropping are both viable strategies for enhancing root colonization from indigenous arbuscular mycorrhizal fungi (AMF) across a wide range of soil types and cash crop species, and possibly also shifting AMF community structure, which could in turn increase biologically based resource use in agricultural systems.

Yield Response to Early Defoliation in Spring‐Planted Canola

Canola (Brassica napus L.) is a high‐value summer annual crop grown in the northern Great Plains of Canada and the United States. During the early stages of its life, the crop may lose leaf area as a result of spring hail storms, frost, herbicides, animal grazing, and insects. However, little information is available on the effect of defoliation during vegetative growth on yield for spring‐planted canola. To address this gap, a five site‐year study was conducted in central Saskatchewan, Canada, to test canola recovery from partial (50%) or full (100%) defoliation at five stages before flowering (2‐, 4‐, 6‐, 8‐, and 10‐leaf stages). Partially defoliated canola plots yielded, on average, 92% of untreated control plots, while fully defoliated canola yielded 75% of controls. The yield response to defoliation timings varied; in one site‐year yield loss was minimized with earlier timings, while in the remaining site‐years, seed yield response was inconsistent or unrelated to timing. Our study shows that partial or full defoliation of summer‐cropped canola at any point during vegetative growth is likely to cause a yield loss. However the crop's substantial compensation for loss of foliage means that reseeding is rarely profitable.

Evaluation of the performance of gum guar varieties in north eastern Karnataka, India

The climatic situation in north eastern parts of Karnataka (except Bidar district) is almost similar to that of Rajastan. There is considerable area under rainfed situations and guar being a highly drought and temperature tolerant summer annual legume crop, there is hope for guar as an alternate and contingent crop during drought year in this region. With this objective effort were made to introduce, evaluate and to identify suitable gum guar varieties for North eastern parts of Karnataka. Ten gum guar varieties developed, released and cultivated in Rajasthan, Haryana and Gujarat state were evaluated in Agricultural Research Stations (ARS) located in Bidar, Gulbarga, Yadgiri, Bellary and Raichur districts of Karnataka during Kharif 2013-14. At Bidar, the top entry with respect to yield was HG-884 (679.00 Kg/ Ha), Variety RGC-1031 (793.00 Kg/Ha) performed well with respect to seed yield in Gulbarga district. Genotypes GAUG-13 (614.00 Kg/Ha) and RGC-986 (501.00 Kg/Ha) recorded higher seed yield respectively, in Bellary and Yadgiri district. At Raichur GAUG-13, recorded highest seed yield of 1432.00 Kg/Ha. Over the locations genotype GAUG-13 recorded highest seed yield of 759.00 Kg/Ha followed by HG-884 (700.40 Kg/Ha) and RGC-986 (696.60 Kg/Ha). The varieties tested exhibited considerable significance differences among themselves at four locations, except at one location (Agricultural Research Station, Bheemarayanagudi, Yadgir district). Variety GAUG-13, recorded highest seed yield over three locations indicating its wider adaptability.

Diverse Rotations and Optimal Cultural Practices Control Wild Oat (Avena fatua)

In western Canada, more money is spent on wild oat herbicides than on any other weed species, and wild oat resistance to herbicides is the most widespread resistance issue. A direct-seeded field experiment was conducted from 2010 to 2014 at eight Canadian sites to determine crop life cycle, crop species, crop seeding rate, crop usage, and herbicide rate combination effects on wild oat management and canola yield. Combining 2× seeding rates of early-cut barley silage with 2× seeding rates of winter cereals and excluding wild oat herbicides for 3 of 5 yr (2011 to 2013) often led to similar wild oat density, aboveground wild oat biomass, wild oat seed density in the soil, and canola yield as a repeated canola–wheat rotation under a full wild oat herbicide rate regime. Wild oat was similarly well managed after 3 yr of perennial alfalfa without wild oat herbicides. Forgoing wild oat herbicides in only 2 of 5 yr from exclusively summer annual crop rotations resulted in higher wild oat density, biomass, and seed banks. Management systems that effectively combine diverse and optimal cultural practices against weeds, and limit herbicide use, reduce selection pressure for weed resistance to herbicides and prolong the utility of threatened herbicide tools.

Sustainable commercialization of new crops for the agricultural bioeconomy

Abstract 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.).