Cover crops provide a variety of important agroecological services within cropping systems. Typically these crops are grown as monocultures or simple graminoid-legume bicultures; however, ecological ...theory and empirical evidence suggest that agroecosystem services could be enhanced by growing cover crops in species-rich mixtures. We examined cover crop productivity, weed suppression, stability, and carryover effects to a subsequent cash crop in an experiment involving a five-species annual cover crop mixture and the component species grown as monocultures in SE New Hampshire, USA in 2011 and 2012. The mean land equivalent ratio (LER) for the mixture exceeded 1.0 in both years, indicating that the mixture over-yielded relative to the monocultures. Despite the apparent over-yielding in the mixture, we observed no enhancement in weed suppression, biomass stability, or productivity of a subsequent oat (Avena sativa L.) cash crop when compared to the best monoculture component crop. These data are some of the first to include application of the LER to an analysis of a cover crop mixture and contribute to the growing literature on the agroecological effects of cover crop diversity in cropping systems.
Agriculture in 2050 HUNTER, MITCHELL C.; SMITH, RICHARD G.; SCHIPANSKI, MEAGAN E. ...
Bioscience,
04/2017, Volume:
67, Issue:
4
Journal Article
Peer reviewed
Open access
The prevailing discourse on the future of agriculture is dominated by an imbalanced narrative that calls for food production to increase dramatically—potentially doubling by 2050—without specifying ...commensurate environmental goals. We aim to rebalance this narrative by laying out quantitative and compelling midcentury targets for both production and the environment. Our analysis shows that an increase of approximately 25%–70% above current production levels may be sufficient to meet 2050 crop demand. At the same time, nutrient losses and greenhouse gas emissions from agriculture must drop dramatically to restore and maintain ecosystem functioning. Specifying quantitative targets will clarify the scope of the challenges that agriculture must face in the coming decades, focus research and policy on achieving specific outcomes, and ensure that sustainable intensification efforts lead to measurable environmental improvements. We propose new directions for research and policy to help meet both sustainability and production goals.
•Pesticide seed treatments may inadvertently affect non-target microbial communities.•They significantly altered rhizosphere and leaf microbial communities of corn and soy.•Rhizosphere and leaf ...microbial communities affect productivity and stress tolerance.
Insecticide and fungicide seed treatments are commonly used to control pests and pathogens in conventional maize and soybean culture, but little is known about their effects on the communities of non-target microbes that inhabit the rhizospheres or leaves of these crops. Because rhizosphere bacterial and fungal communities influence carbon and nutrient turnover, nutrient transformation, nutrient uptake and disease suppression, and because leaf endophyte fungal communities influence many aspects of stress tolerance in plants, any effect of a pesticide seed treatment on these microbial communities could have unintended and possibly adverse effects on seedling performance. We conducted a three-year field experiment in which maize (2013, 2015) and soybean (2014) were grown in rotation from seeds that were either coated or not coated with common pesticide treatments, which included contact and systemic fungicides and systemic insecticides. We sampled seedling rhizosphere soil (maize in 2013, soybean in 2014) and seedling leaves (soybean in 2014, maize in 2015) and characterized their microbial communities. For maize, the rhizosphere fungal and bacterial communities were significantly affected by the seed treatment, but leaf endophytic fungal communities were not. For soybean, the rhizosphere fungal community was significantly affected, as was the leaf endophytic fungal community, but not the rhizosphere bacterial community. These results show that pesticide seed treatments may affect rhizosphere soil microbial communities and endophytic leaf fungal communities more than one month after planting and, therefore, may have significant, unintended effects on non-target organisms. Additional research must determine the consequences of these effects and the nature of their context dependency.
Cover crops represent a potentially important biological filter during weed community assembly in agroecosystems. This filtering could be considered directional if different cover-crop species result ...in weed communities with predictably different species composition. We examined the following four questions related to the potential filtering effects of cover crops in a field experiment involving five cover crops grown in monoculture and mixture: (1) Do cover crops differ in their effect on weed community composition? (2) Is competition more intense between cover crops and weeds that are in the same family or functional group? (3) Is competition more intense across weed functional types in a cover-crop mixture compared with cover crops grown in monocultures? (4) Within a cover-crop mixture, is a higher seeding rate associated with more effective biotic filtering of the weed community? We found some evidence that cover crops differentially filtered weed communities and that at least some of these filtering effects were due to differential biomass production across cover-crop species. Monocultures of buckwheat and sorghum–sudangrass reduced the number of weed species relative to the no-cover-crop control by an average of 36 and 59% (buckwheat) and 25 and 40% (sorghum–sudangrass) in 2011 and 2012, respectively. We found little evidence that competition intensity was dependent upon the family or functional classification of the cover crop or weeds, or that cover-crop mixtures were stronger assembly filters than the most effective monocultures. Although our results do not suggest that annual cover crops exert strong directional filtering during weed community assembly, our methodological framework for detecting such effects could be applied to similar future studies that incorporate a greater number of cover-crop species and are conducted under a greater range of cover-cropping conditions. Nomenclature: Buckwheat, Fagopyrum esculentum Moench; cereal rye, Secale cereal L.; field pea, Pisum sativum L.; hairy vetch, Vicia villosa Roth; mustard, Brassica juncea (L.) Czern.; sorghum–sudangrass, Sorghum bicolor × S. bicolor var. sudanese.
•Pesticide seed treatments are common in large acreage row crops.•Natural enemies of weed seeds may be affected by pesticides.•Pesticide seed treatments reduced the diversity of the soil seed ...bank.•Trends in weed seed density, richness and evenness were consistent with our hypotheses.
Use of pesticide seed treatments (coating seeds with insecticides and/or fungicides) is a common practice in conventional maize and soybean production. Despite their widespread use, however, little is known about how this practice affects soil food webs and their associated ecosystem services. We conducted a two-year field experiment in central Pennsylvania, USA in which identical genotypes of maize (2013) and soybean (2014) were planted with and without pesticide seed treatments in a completely randomized design with five replications. We sampled the weed seed bank during both the corn (fall 2013) and soybean (summer 2014) phases of the rotation. After each sampling event, soil samples were transported to a temperature-controlled greenhouse facility and weed seed bank composition and density was assessed over a period of four months via the direct germination method. Seed bank data were analyzed with ANOVA and several multivariate techniques to determine the effect of pesticide seed treatments on seed bank density, diversity, and species composition. We hypothesized that pesticide seed treatments reduce the abundance of natural enemies (e.g., soil-dwelling seed predators and pathogens) that damage or destroy weed seeds in the soil, and therefore seed banks in treated plots would be larger and less diverse than those in untreated plots. In accordance with our hypothesis, weed seed banks were significantly less diverse in treated compared to untreated control plots (Shannon and Simpson’s indices of diversity, p<0.05). While not statistically significant, differences in mean germinable weed seed bank density, richness, and evenness were also in the direction that we hypothesized. These data provide the first evidence that we are aware of that weed seed banks, and hence weed populations, may be indirectly affected by pesticide seed treatments. Additional research will be necessary to determine the generality of these responses and their underlying mechanisms.
There is increasing global demand for food, bioenergy feedstocks and a wide variety of bio-based products. In response, agriculture has advanced production, but is increasingly depleting soil ...regulating and supporting ecosystem services. New production systems have emerged, such as no-tillage, that can enhance soil services but may limit yields. Moving forward, agricultural systems must reduce trade-offs between production and soil services. Soil functional zone management (SFZM) is a novel strategy for developing sustainable production systems that attempts to integrate the benefits of conventional, intensive agriculture, and no-tillage. SFZM creates distinct functional zones within crop row and inter-row spaces. By incorporating decimeter-scale spatial and temporal heterogeneity, SFZM attempts to foster greater soil biodiversity and integrate complementary soil processes at the sub-field level. Such integration maximizes soil services by creating zones of 'active turnover', optimized for crop growth and yield (provisioning services); and adjacent zones of 'soil building', that promote soil structure development, carbon storage, and moisture regulation (regulating and supporting services). These zones allow SFZM to secure existing agricultural productivity while avoiding or minimizing trade-offs with soil ecosystem services. Moreover, the specific properties of SFZM may enable sustainable increases in provisioning services via temporal intensification (expanding the portion of the year during which harvestable crops are grown). We present a conceptual model of 'virtuous cycles', illustrating how increases in crop yields within SFZM systems could create self-reinforcing feedback processes with desirable effects, including mitigation of trade-offs between yield maximization and soil ecosystem services. Through the creation of functionally distinct but interacting zones, SFZM may provide a vehicle for optimizing the delivery of multiple goods and services in agricultural systems, allowing sustainable temporal intensification while protecting and enhancing soil functioning.
ABSTRACT
Increasingly, funding agencies are investing in integrated and transdisciplinary research to tackle “grand challenge” priority areas, critical for sustaining agriculture and protecting the ...environment. Coordinating multidisciplinary research teams capable of addressing these priority areas, however, presents its own unique set of challenges, ranging from bridging across multiple disciplinary perspectives to achieve common questions and methods to facilitating engagement in holistic and integrative thinking that promotes linkages from scholarship to societal needs. We propose that structural equation modeling (SEM) can provide a powerful framework for synergizing multidisciplinary research teams around grand challenge issues. Structural equation modeling can integrate both visual and statistical expression of complex hypotheses at all stages of the research process, from planning to analysis. Three elements of the SEM framework are particularly beneficial to multidisciplinary research teams; these include (i) a common graphical language that transcends disciplinary boundaries, (ii) iterative, critical evaluation of complex hypotheses involving manifest and latent variables and direct and indirect interactions, and (iii) enhanced opportunities to discover unanticipated interactions or causal pathways as empirical data are tested statistically against the model. Using our ongoing multidisciplinary, multisite field investigation of climate change adaptation and mitigation in annual row crop agroecosystems as a case study, we demonstrate the value of the SEM framework for project design, coordination, and implementation and provide recommendations for its broader application as a means to more effectively engage and address issues of critical societal concern.
The use of pesticide seed treatments containing neonicotinoid insecticides is widespread in large-scale row crop agriculture. Recently, use of pesticide seed treatments has come under scrutiny due to ...concerns over non-target impacts on beneficial insects (e.g., honey bees) and the environment. Amidst these growing concerns, however, few studies have examined how pesticide seed treatments may impact soil faunal communities across multiple feeding guilds and the soil processes they regulate. We grew corn and soybean with and without pesticide seed treatment for three years and measured the response of the soil faunal detritivore, herbivore, mixed, and predator feeding guilds, nitrogen mineralization, and surface litter decomposition at three time points each year. We found the effects of seed treatment on the soil faunal community varied in direction and magnitude by year and feeding guild and were most apparent in the predator and detritivore guilds. Guild-level effects tended to be strongest soon after planting but remained apparent throughout the crop growing season, particularly in the predator and mixed feeding guilds. We found no evidence that pesticide seed treatment affected the herbivore guild—the intended target of the seed treatment, or nitrogen mineralization, surface litter decomposition, or grain yields. Collectively, these data suggest that pesticide seed treatments can alter the abundance, richness, and diversity of all non-targeted soil faunal guilds. Additional research will be necessary to determine the longer-term significance of pesticide seed treatment-driven changes in non-target soil faunal communities in agroecosystems.
•Response of soil faunal community to neonicotinoid seed treatments.•The abundance and/or composition of all feeding guilds was affected.•One herbivore taxon (Symphyla) increased in the presence of seed treatments.•Predator guild response to seed treatments varied by year and sampling time.•Changes in the soil community did not alter the soil-driven processes examined.
Increased hurricane frequency and intensity and residential and commercial development are contributing to loss of maritime forests, coastal hammocks, and scrub dunes. Barriers to natural ...regeneration necessitate active restoration. We evaluated the survival of woody species planted in ephemeral barrier island swales on Santa Rosa Island, Florida, in an effort to restore barrier island scrub and pine forest lost in recent hurricanes. Contractors planted sand live oak (Quercus geminata) on swale ridges, inkberry (Ilex glabra) on swale mid-slopes, and slash pine (Pinus elliottii) in swale depressions. Polyacrylamide gels are often used to increase transplant survival in the drought-prone, sandy environments. To assist us in evaluating the efficacy of these gels, contractors planted 10 plants with gel and 10 without for each swale, position, and woody species. We followed plant survival for 21 months and measured changes in plant height after one year. Polyacrylamide gel did not significantly affect survival of slash pine or sand live oak. Less than 25% of slash pine and sand live oak survived after 21 months. We found initial survival of inkberry was greater with than without gel, but plant death continued; and after eight weeks, we found no difference in survival for inkberry planted with and without gel. Inkberry survival declined to < 5% at the last evaluation. Changes in plant height were also not affected by Polyacrylamide gel. We do not recommend the use of Polyacrylamide gel to replace supplemental water or to replace the planting of deeply rooted plants on barrier islands.
Restoration of woody plants to barrier islands requires development of production and outplanting protocols as well as determination of "safe sites" for reestablishment. Yaupon (Ilex vomitoria Aiton ...Aquifoliaceae) is a shrub associated with scrub dunes and shallow, interdunal swales of barrier islands along the northern Gulf Coast. We studied the effect of microsite (lowest point of the depression within interdunal swale versus low dune ridge around swale), rooting depth (production container depth), and absorbing gel on seedling survival and subsequent growth of I. vomitoria planted at 5 sites associated with barrier island swales of Santa Rosa Island, Florida. Survival of I. vomitoria was greater in depressions than on ridges and with greater rooting depths. Survival on ridges did not improve with addition of hydrogel but survival for standard pots was increased in depressions. When outplanted in depressions with gel, plant height increased by as much as 6 cm (2.4 in) compared to all other outplanting combinations. Plants on ridges were half the height of plants in depressions in 2006 but no differences were found in 2007. Plants grown in Treepots were more than twice as tall as plants grown in round containers in 2006 but did not differ in 2007. Plants had greater canopy area in depressions than on ridges and with greater rooting depth. For establishment and growth on barrier islands, I. vomitoria should be grown in pots 35 cm (14 in) deep (for example, Treepots) and planted in centers of shallow swales.
PDF
