• Authors:
    • Stone, J. J.
    • Moriles-Miller, J.
    • Carlson, C. G.
    • Reicks, G.
    • Clay, D. E.
    • Clay, S. A.
  • Source: Journal of Environmental Quality
  • Volume: 44
  • Issue: 3
  • Year: 2015
  • Summary: Corn stover harvesting is a common practice in the western U.S. Corn Belt. This 5-yr study used isotopic source tracking to quantify the influence of two tillage systems, two corn ( Zea mays L.) surface residue removal rates, and two yield zones on soil organic C (SOC) gains and losses at three soil depths. Soil samples collected in 2008 and 2012 were used to determine 13C enrichment during SOC mineralization, the amount of initial SOC mineralized (SOC lost), and plant C retained in the soil (PCR incorp) and sequestered C (PCR incorp - SOC lost). The 30% residue soil cover after planting was achieved by the no-till and residue returned treatments and was not achieved by the chisel plow, residue removed treatment. In the 0- to 15-cm soil depth, the high yield zone had lower SOC loss (1.49 Mg ha -1) than the moderate yield zone (2.18 Mg ha -1), whereas in the 15- to 30-cm soil depth, SOC loss was higher in the 60% (1.38 Mg ha -1) than the 0% (0.82 Mg ha -1) residue removal treatment. When the 0- to 15- and 15- to 30-cm soil depths were combined, (i) 0.91 and 3.62 Mg SOC ha -1 were sequestered in the 60 and 0% residue removal treatments; (ii) 2.51 and 0.36 Mg SOC ha -1 were sequestered in the no-till and chisel plow treatments, and (iii) 1.16 and 1.65 Mg SOC ha -1 were sequestered in the moderate and high yield zone treatments, respectively. The surface treatments influenced C cycling in the 0- to 15- and 15- to 30-cm depths but did not influence SOC turnover in the 30- to 60-cm depth.
  • Authors:
    • Ngouajio, M.
    • Hayden, Z. D.
    • Brainard, D. C.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Mixtures of cereal rye ( Secale cereale L.) and the legume hairy vetch ( Vicia villosa Roth) are used to provide fixed N in balance with other important cover crop services, but late planting and interference from rye can limit vetch productivity. This 2-yr study in Michigan investigated how fall planting dates influence rye-vetch cover crop biomass quantity and quality in the spring, and evaluated whether staggering (delaying) rye seeding could improve vetch performance (biomass production, N fixation, and winter survival) in mixtures. Treatments consisted of a two-way factorial of three vetch planting dates (late August, mid-September, and late September) and three lengths of rye seeding stagger (co-seeded, short stagger, and long stagger). Later planting of co-seeded mixtures generally led to reduced total shoot biomass and lower proportions of vetch, resulting in cover crop residues with less vetch N and a higher total C/N. For earlier planting dates, delaying rye seeding until vetch emergence (short stagger) increased vetch shoot biomass by 760 to 1060 kg ha -1 (30-36 kg vetch N ha -1) relative to co-seeding. Staggered seeding provided no benefit to vetch biomass at later planting dates, and delaying rye seeding until the vetch three to four leaf stage (long stagger) reduced vetch winter survival by 12 to 42% compared with co-seeding. Additional research is needed to determine whether potential on-farm benefits of rye-vetch staggered seeding justify the additional management complexity involved and possible tradeoffs with other cover crop services.
  • Authors:
    • Woodward, R.
    • Jones, M.
    • Stoller, J.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Spatial variation from soil and related factors often affects the outcome of agronomic field experiments. The randomized complete block (RCB) is the most prevalent design despite inefficiencies that can result in inflated error terms. Experimental designs such as the Latin square (LS) allow for bidirectional blocking and offer the potential to account for spatial variability better. The objectives of this research were to investigate the occurrence of two-way gradients in agronomic field trials and compare the estimated relative efficiency (ERE) of a LS to a RCB. Thirty LS trials were evaluated in 10 states during 2013 across the midwestern United States investigating crop yields of corn ( Zea mays L.), soybean [ Glycine max (L.) Merr.], and sorghum [ Sorghum bicolor (L.) Moench]. The results show that 47% of the trials exhibited a two-way gradient, indicating this characteristic is widespread across a large geographic region. Overall, the ERE was increased in 70% of the trials by using the LS design. A lower ERE occurred in 7% of the trials conducted using a LS. Multiple gradients appear common in agronomic field plot trials and enough variation existed between the two blocking directions to justify the use of a LS design. Our data indicate the LS offers a low risk, high reward option of experimental design for controlling spatial heterogeneity and increasing precision. When possible, the LS design should be used in field experiments where the trial area appears uniform and gradients to block against are not obvious.
  • Authors:
    • Freycon, V.
    • Laumonier, Y.
    • Locatelli, B.
    • Labriere, N.
    • Bernoux, M.
  • Source: Agricultural Journal
  • Volume: 203
  • Year: 2015
  • Summary: Healthy soils provide a wide range of ecosystem services. But soil erosion (one component of land degradation) jeopardizes the sustainable delivery of these services worldwide, and particularly in the humid tropics where erosion potential is high due to heavy rainfall. The Millennium Ecosystem Assessment pointed out the role of poor land-use and management choices in increasing land degradation. We hypothesized that land use has a limited influence on soil erosion provided vegetation cover is developed enough or good management practices are implemented. We systematically reviewed the literature to study how soil and vegetation management influence soil erosion control in the humid tropics. More than 3600 measurements of soil loss from 55 references covering 21 countries were compiled. Quantitative analysis of the collected data revealed that soil erosion in the humid tropics is dramatically concentrated in space (over landscape elements of bare soil) and time (e.g. during crop rotation). No land use is erosion-prone per se, but creation of bare soil elements in the landscape through particular land uses and other human activities (e.g. skid trails and logging roads) should be avoided as much as possible. Implementation of sound practices of soil and vegetation management (e.g. contour planting, no-till farming and use of vegetative buffer strips) can reduce erosion by up to 99%. With limited financial and technical means, natural resource managers and policy makers can therefore help decrease soil loss at a large scale by promoting wise management of highly erosion-prone landscape elements and enhancing the use of low-erosion-inducing practices.
  • Authors:
    • Keeton, W. S.
    • Mika, A. M.
  • Source: Research Article
  • Volume: 7
  • Issue: 3
  • Year: 2015
  • Summary: The long-term greenhouse gas emissions implications of wood biomass ('bioenergy') harvests are highly uncertain yet of great significance for climate change mitigation and renewable energy policies. Particularly uncertain are the net carbon (C) effects of multiple harvests staggered spatially and temporally across landscapes where bioenergy is only one of many products. We used field data to formulate bioenergy harvest scenarios, applied them to 362 sites from the Forest Inventory and Analysis database, and projected growth and harvests over 160 years using the Forest Vegetation Simulator. We compared the net cumulative C fluxes, relative to a non-bioenergy baseline, between scenarios when various proportions of the landscape are harvested for bioenergy: 0% (non-bioenergy); 25% (BIO25); 50% (BIO50); or 100% (BIO100), with three levels of intensification. We accounted for C stored in aboveground forest pools and wood products, direct and indirect emissions from wood products and bioenergy, and avoided direct and indirect emissions from fossil fuels. At the end of the simulation period, although 82% of stands were projected to maintain net positive C benefit, net flux remained negative (i.e., net emissions) compared to non-bioenergy harvests for the entire 160-year simulation period. BIO25, BIO50, and BIO100 scenarios resulted in average annual emissions of 2.47, 5.02, and 9.83 Mg C ha -1, respectively. Using bioenergy for heating decreased the emissions relative to electricity generation as did removing additional slash from thinnings between regeneration harvests. However, all bioenergy scenarios resulted in increased net emissions compared to the non-bioenergy harvests. Stands with high initial aboveground live biomass may have higher net emissions from bioenergy harvest. Silvicultural practices such as increasing rotation length and structural retention may result in lower C fluxes from bioenergy harvests. Finally, since passive management resulted in the greatest net C storage, we recommend designation of unharvested reserves to offset emissions from harvested stands.
  • Authors:
    • Arbuckle, J. G.
    • Hobbs, J.
    • Morton, L. W.
    • Loy, A.
  • Source: Web Of Knowledge
  • Volume: 44
  • Issue: 3
  • Year: 2015
  • Summary: Persistent above average precipitation and runoff and associated increased sediment transfers from cultivated ecosystems to rivers and oceans are due to changes in climate and human action. The US Upper Midwest has experienced a 37% increase in precipitation (1958-2012), leading to increased crop damage from excess water and off-farm loss of soil and nutrients. Farmer adaptive management responses to changing weather patterns have potential to reduce crop losses and address degrading soil and water resources. This research used farmer survey ( n=4778) and climate data (1971-2011) to model influences of geophysical context, past weather, on-farm flood and saturated soils experiences, and risk and vulnerability perceptions on management practices. Seasonal precipitation varied across six Upper Midwest subregions and was significantly associated with variations in management. Increased warm-season precipitation (2007-2011) relative to the past 40 yr was positively associated with no-till, drainage, and increased planting on highly erodible land (HEL). Experience with saturated soils was significantly associated with increased use of drainage and less use of no-till, cover crops, and planting on HEL. Farmers in counties with a higher percentage of soils considered marginal for row crops were more likely to use no-till, cover crops, and plant on HEL. Respondents who sell corn through multiple markets were more likely to have planted cover crops and planted on HEL in 2011. This suggests that regional climate conditions may not well represent individual farmers' actual and perceived experiences with changing climate conditions. Accurate climate information downscaled to localized conditions has potential to influence specific adaptation strategies.
  • Authors:
    • Mallarino, A. P.
    • Pagani, A.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: It is known that soil acidity can limit crop yield, but additional research is needed to identify more precisely optimum soil pH for corn ( Zea mays L.) and soybean [ Glycine max (L.) Merr.] and the within-field variation in yield response to liming. The objective of this study was to identify optimum soil pH for these crops by studying the variation of soil pH and grain yield response to liming within several Iowa fields. Fourteen 4-yr strip-trials were established in acidic Molisols from 2007 to 2009. The methodology used global positioning systems (GPS), dense soil sampling (0.12-0.18-ha cells), yield monitors, and geographical information systems (GIS). One-time treatments replicated two to five times were an unlimed control and limestone at 6.72 Mg ha -1 effective calcium carbonate equivalent (ECCE), incorporated into the soil in fields managed with tillage. Soil samples (15-cm depth) were collected before liming and annually after crop harvest. The lowest initial soil pH at each site ranged from 4.75 to 5.70. Maximum pH increase was reached 1 to 3 yr after liming. Grain yield response to lime varied greatly. Corn yield responded more frequently than soybean yield but the magnitude of the response did not differ consistently. Liming seldom increased yield with pH>6.0 in soils having a high subsoil pH (≥7.4) and CaCO 3 within a 1-m depth but often increased yield up to pH 6.5 with lower pH subsoil. The results provided improved criteria for site-specific soil pH and lime management.
  • Authors:
    • Prokopy,Linda Stalker
    • Carlton,J. Stuart
    • Arbuckle,J. Gordon, Jr.
    • Haigh,Tonya
    • Lemos,Maria Carmen
    • Mase,Amber Saylor
    • Babin,Nicholas
    • Dunn,Mike
    • Andresen,Jeff
    • Angel,Jim
    • Hart,Chad
    • Power,Rebecca
  • Source: Climatic Change
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: The U.S. Cooperative Extension Service was created 100 years ago to serve as a boundary or interface organization between science generated at the nation's land grant universities and rural communities. Production agriculture in the US is becoming increasingly complex and challenging in the face of a rapidly changing climate and the need to balance growing crop productivity with environmental protection. Simultaneously, extension budgets are diminishing and extension personnel are stretched thin with numerous, diverse stakeholders and decreasing budgets. Evidence from surveys of farmers suggests that they are more likely to go to private retailers and consultants for information than extension. This paper explores the role that extension can play in facilitating climate change adaptation in agriculture using data from a survey of agricultural advisors in Indiana, Iowa, Michigan and Nebraska and a survey of extension educators in the 12 state North Central Region. Evidence from these surveys shows that a majority of extension educators believe that climate change is happening and that they should help farmers prepare. It also shows that private agricultural advisors trust extension as a source of information about climate change. This suggests that extension needs to continue to foster its relationship with private information providers because working through them will be the best way to ultimately reach farmers with climate change information. However extension educators must be better informed and trained about climate change; university specialists and researchers can play a critical role in this training process.
  • Authors:
    • Helmers, M. J.
    • Kostel, J. A.
    • James, D. E.
    • Boomer, K. M. B.
    • Porter, S. A.
    • Tomer, M. D.
    • Isenhart, T. M.
    • McLellan, E.
  • Source: Agronomy Journal
  • Volume: 44
  • Issue: 3
  • Year: 2015
  • Summary: Spatial data on soils, land use, and topography, combined with knowledge of conservation effectiveness, can be used to identify alternatives to reduce nutrient discharge from small (hydrologic unit code [HUC]12) watersheds. Databases comprising soil attributes, agricultural land use, and light detection and ranging-derived elevation models were developed for two glaciated midwestern HUC12 watersheds: Iowa's Beaver Creek watershed has an older dissected landscape, and Lime Creek in Illinois is young and less dissected. Subsurface drainage is common in both watersheds. We identified locations for conservation practices, including in-field practices (grassed waterways), edge-of-field practices (nutrient-removal wetlands, saturated buffers), and drainage-water management, by applying terrain analyses, geographic criteria, and cross-classifications to field- and watershed-scale geographic data. Cover crops were randomly distributed to fields without geographic prioritization. A set of alternative planning scenarios was developed to represent a variety of extents of implementation among these practices. The scenarios were assessed for nutrient reduction potential using a spreadsheet approach to calculate the average nutrient-removal efficiency required among the practices included in each scenario to achieve a 40% NO 3-N reduction. Results were evaluated in the context of the Iowa Nutrient Reduction Strategy, which reviewed nutrient-removal efficiencies of practices and established the 40% NO 3-N reduction as Iowa's target for Gulf of Mexico hypoxia mitigation by agriculture. In both test watersheds, planning scenarios that could potentially achieve the targeted NO 3-N reduction but remove <5% of cropland from production were identified. Cover crops and nutrient removal wetlands were common to these scenarios. This approach provides an interim technology to assist local watershed planning and could provide planning scenarios to evaluate using watershed simulation models. A set of ArcGIS tools is being released to enable transfer of this mapping technology.
  • Authors:
    • Shonnard, D.
    • Archer, D.
    • Beck, E.
    • Ukaew, S.
  • Source: Journal
  • Volume: 20
  • Issue: 5
  • Year: 2015
  • Summary: Rapeseed is being considered as a potential feedstock for hydrotreated renewable jet (HRJ) fuel in the USA through its cultivation in rotation with wheat. The goal of this research was to determine the impact of soil C changes, induced through replacing the fallow period with rapeseed in rotation with wheat, and the effects it would have on emission of greenhouse gases (GHG) of rapeseed HRJ. The Intergovernmental Panel on Climate Change (IPCC) (Tier 1) method was used with modifications to determine the changes in soil C of wheat-wheat-rapeseed (WWR) relative to the reference wheat-wheat-fallow (WWF) rotation for 20 years of cultivation. The 27 case scenarios were conducted to study the impacts of changes in management practices (tillage practice and residue input) on changes in soil C for WWR rotation in multiple locations in 10 US states. The CO2 emissions resulting from soil C changes were incorporated into the rapeseed HRJ pathway in order to evaluate the GHG emissions. Introducing rapeseed to replace the fallow period with wheat could either increase or decrease changes in soil C, depending on management practices. Soil C is predicted to increase with increased residue input and reduced tillage. The greatest gain of soil C was found when using high residue input for wheat and rapeseed under no tillage, resulting in the best management practice. Conversely, adding low residue input to both crops with full tillage created the highest loss of soil C, referring to as the worst management practice. Soil C changes varied across locations from -0.22 to 0.32 Mg C ha(-1) year(-1). Consequently, the GHG emissions of rapeseed HRJ ranged from 4 to 70 g CO2 eq./MJ, comparing to 46 g CO2 eq./MJ for excluding soil C change. The rapeseed HRJ exhibited the GHG savings of 65-96 % for the best practice and 20-42 % for the worst practice when compared to petroleum jet fuel. Based on results using the modified IPCC method, adoption of high residue input with no tillage for the rotation cropping of rapeseed with wheat had the potential to increase soil C. However, the method has limitations for predicting soil C changes regarding crop management practices. Biogeochemical-based models that have a potential to capture processes of C and N dynamics in soil and yield may be better suited to quantify regional variations in soil C changes for the rotation cropping of rapeseed with wheat.