• Authors:
    • Islam, K. R.
    • Mahmood, T.
    • Bangash, N.
    • Aziz, I.
  • Source: Pakistan Journal of Botany
  • Volume: 47
  • Issue: 1
  • Year: 2015
  • Summary: There is a global concern about progressive increase in the emission of greenhouse gases especially atmosphere CO2. An increasing awareness about environmental pollution by CO2 emission has led to recognition of the need to enhance soil C sequestration through sustainable agricultural management practices. Conservation management systems such as no-till (NT) with appropriate crop rotation have been reported to increase soil organic C content by creating less disturbed environment. The present study was conducted on Vanmeter farm of The Ohio State University South Centers at Piketon Ohio, USA to estimate the effect of different tillage practices with different cropping system on soil chemical properties. Tillage treatments were comprised of conventional tillage (CT) and No-till (NT). These treatments were applied under continuous corn (CC), corn-soybean (CS) and corn-soybean-wheat-cowpea (CSW) cropping system following randomized complete block design. No-till treatment showed significant increase in total C (30%), active C (10%), and passive salt extractable (18%) and microwave extractable C (8%) and total nitrogen (15%) compared to conventional tillage practices. Total nitrogen increased significantly 23 % in NT over time. Maximum effect of no-till was observed under corn-soybean-wheat-cowpea crop rotation. These findings illustrated that no-till practice could be useful for improving soil chemical properties.
  • 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:
    • Kovacs, P.
    • Omonode, R. A.
    • Vyn, T. J.
  • Source: Article
  • Volume: 107
  • Issue: 2
  • Year: 2015
  • Summary: Precision-guided technologies enable corn ( Zea mays L.) growers to apply pre-plant anhydrous ammonia (NH 3) parallel to intended corn rows even when full-width tillage follows NH 3 application. Close, but crop-safe, proximity of NH 3 to corn rows may potentially increase N use efficiency and lower N requirements and nitrous oxide (N 2O) emissions. Experiments in 2011 and 2012 on silty clay loam Mollisol near West Lafayette, IN, assessed area- and yield-scaled N 2O emissions when spring pre-plant NH 3 was applied at recommended (202 kg N ha -1) and reduced rate (145 kg N ha -1), in no-till (NT) and conventional tillage (CT) systems following NT soybean [ Glycine max (L.) Merr.]. Each 12-cm deep NH 3 band was positioned 15 cm from, and parallel to, intended corn rows using precision guidance. Nitrification of NH 3 in application bands was 31% faster under CT than NT. Area- and grain yield-scaled N 2O emissions were N rate dependent in both growing seasons. On average, CT+202 kg N resulted in highest area-scaled (mean=2.45 kg N ha -1) and grain yield-scaled (mean=360 g N Mg -1) N 2O emissions. In contrast, CT+145 kg N had similar yield-scaled emissions as NT+202 and NT+145 kg N, and reduced area-scaled N 2O emissions by 65, 45, and 19% respectively, relative to CT+202 kg N, NT+202 kg N, and NT+145 kg N treatments. These preliminary results suggest that reducing pre-plant NH 3 rates by ~30% under CT has the potential to reduce N 2O emissions without significant yield declines in the CT phase of a NT-CT rotation, despite faster nitrification in CT.
  • 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:
    • Savabi, M. R.
    • Abdo, Z.
    • Sullivan, D. G.
    • Hubbard, R. K.
    • Scully, B. T.
    • Strickland, T. C.
    • Lee, R. D.
    • Olson, D. M.
    • Hawkins, G. L.
  • Source: Soil and Water Journal
  • Volume: 70
  • Issue: 3
  • Year: 2015
  • Summary: Although conservation tillage is widely believed to be an agricultural management practice effective for increasing soil carbon (C) accretion and associated soil quality, there is limited research to determine whether conservation tillage increases net C accretion versus simply altering the distribution of C content by soil depth. We implemented conservation farming practices (winter cover cropping plus strip tillage) for a nonirrigated corn (Zea mays L.) production system in the southeastern coastal plain of Georgia, United States, that had been previously managed under a conventional plow and harrow tillage regime. Total soil C and nitrogen (N) were measured on samples collected from 0 to 65 cm (0 to 25.6 in) at 57 sites before and after five years under conservation farming practices. Crop yield, winter and summer aboveground crop biomass production, and biomass C and N content were also measured annually at each site. Soil C increased an average of 20 Mg ha-1 (8.9 tn ac-1; 6 to 62 Mg C ha-1 [2.6 to 27.6 tn C ac-1], depending upon slope position) and was associated with a N increase of 2 Mg ha-1 (0.89 tn ac-1). Although 72% to 80% of the C accretion was in the top 35 cm (13.8 in), 3 to 6 Mg C ha-1 (1.3 to 2.6 tn C ac-1) was accreted from 35 to 65 cm (13.8 to 25.6 in). The soil C accreted during the study amounted to 36% of the net biomass C produced. Corn yield increased 2,200 kg ha-1 (1,964 lb ac-1) depending upon slope position (1,200 to 2,500 kg ha-1 [1,071 to 2,232 lb ac-1]) during the same time. Analysis indicated that soil C content from 15 to 35 cm (5.9 to 13.8 in) was the soil parameter primarily associated with corn yield. Season rainfall from planting to corn silking stage for both corn production years was the lowest in the past 45 years (20 to 25 cm [7.8 to 9.8 in] below the net crop demand) suggesting that soil C-mediated increase in plant-available soil water was a mechanism contributing to improved corn yield. Calculated estimates (from soil clay, sand, and C content) of increased soil water holding capacity suggest that C accretion in the top 35 cm (13.8 in) of soil potentially increased water storage enough to supply up to four days' worth of additional crop water demand. These results indicated that conservation farming practices can increase soil C and N accretion in degraded sandy soils of the humid southeastern United States coastal plain, and that increased soil C may potentially mitigate the deleterious effects of short-term rainfall deficits in nonirrigated production systems.
  • Authors:
    • Coulter, J. A.
    • Venterea, R. T.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Modification of N fertilizer application timing within the growing season has the potential to reduce soil nitrous oxide (N 2O) emissions but limited data are available to assess its effects. We compared cumulative growing season nitrous oxide emissions (cN 2O) following urea applied to corn ( Zea mays L.) in a single application (SA) at planting or in three split applications (SpA) over the growing season. For both SA and SpA, granular urea was broadcast and incorporated at six fertilizer N rates in the corn phase of a corn-soybean [ Glycine max (L.) Merr.] rotation and in a continuous corn system over two growing seasons. Daily N 2O flux was measured using chambers on 35 dates in 2012 and 40 dates in 2013 and soil nitrate-N concentration was measured weekly. Split application did not affect grain yield and did not reduce cN 2O. Across N rates and rotations, cN 2O was 55% greater with SpA compared with SA in 2012. Increased cN 2O with SpA in 2012 likely resulted from a prolonged dry period before the second split application followed by large rainfall events following the third split application. Across years and rotations, SpA increased cN 2O by 57% compared with SA when the maximum N rate was applied. Exponential relationships between cN 2O and fertilizer N rate explained 62 to 74% of the variance in area-based cN 2O and 54% of the variance in yield-based cN 2O. Applying urea to coincide with periods of high crop N demand does not necessarily reduce and may increase N 2O emissions.
  • Authors:
    • Suh, S. W.
    • Yang, Y.
  • Source: Article
  • Volume: 20
  • Issue: 2
  • Year: 2015
  • Summary: Purpose: Previous estimates of carbon payback time (CPT) of corn ethanol expansion assumed that marginal yields of newly converted lands are the same as the average corn yield, whereas reported marginal yields are generally lower than the average yield (47-83% of average yield). Furthermore, these estimates assumed that the productivity of corn ethanol system and climate change impacts per unit greenhouse gas (GHG) emissions remain the same over decades to a century. The objective of this study is to re-examine CPT of corn ethanol expansion considering three aspects: (1) yields of newly converted lands (i.e., marginal yield), (2) technology improvements over time within the corn ethanol system, and (3) temporal sensitivity of climate change impacts. Methods: A new approach to CPT calculation is proposed, where changes in productivity of ethanol conversion process and corn yield are taken into account. The approach also allows the use of dynamic characterization approach to GHGs emitted in different times, as an option. Data are collected to derive historical trends of bioethanol conversion efficiency and corn yield, which inform the development of the scenarios for future biofuel conversion efficiency and corn yield. Corn ethanol's CPTs are estimated and compared for various marginal-to-average (MtA) yield ratios with and without considering technology improvements and time-dependent climate change impacts. Results and discussion: The results show that CPT estimates are highly sensitive to both MtA yield ratio and productivity of ethanol system. Without technological advances, our CPT estimates for corn ethanol from newly converted Conservation Reserve Program (CRP) land exceed 100 years for all MtA yield ratios tested except for the case where MtA yield ratio is 100%. When the productivity improvements within corn ethanol systems since previous CPT estimates and their future projections are considered, our CPT estimates fall into the range of 15 years (100% MtA yield ratio) to 56 years (50% MtA yield ratio), assuming land conversion takes place in early 2000s. Incorporating diminishing sensitivity of GHG emissions to future emissions year by year, however, increases the CPT estimates by 57 to 13% (from 17 years for 100% MtA yield ratio to 88 years for 50% MtA yield ratio). For 60 MtA yield ratio, CPT is estimated to be 43 years, which is relatively close to previous CPT estimates (i.e., 40 to 48 years) but with very different underlying reasons. Conclusions: This study highlights the importance of considering technological advances in understanding the climate change implications of land conversion for corn ethanol. Without the productivity improvements in corn ethanol system, the prospect of paying off carbon debts from land conversion within 100 years becomes unlikely. Even with the ongoing productivity improvements, the yield of newly converted land can significantly affect the CPT. The results reinforce the importance of considering marginal technologies and technology change in prospective life cycle assessment.
  • Authors:
    • Grosso, S. J.
    • Spatari, S.
    • Pourhashem, G.
    • Mitchell, J. G.
    • Adler, P. R.
    • Parton, W. J.
  • Source: Research Article
  • Volume: 25
  • Issue: 4
  • Year: 2015
  • Summary: Crop residues are potentially significant sources of feedstock for biofuel production in the United States. However, there are concerns with maintaining the environmental functions of these residues while also serving as a feedstock for biofuel production. Maintaining soil organic carbon (SOC) along with its functional benefits is considered a greater constraint than maintaining soil erosion losses to an acceptable level. We used the biogeochemical model DayCent to evaluate the effect of residue removal, corn stover, and wheat and barley straw in three diverse locations in the USA. We evaluated residue removal with and without N replacement, along with application of a high-lignin fermentation byproduct (HLFB), the residue by-product comprised of lignin and small quantities of nutrients from cellulosic ethanol production. SOC always decreased with residue harvest, but the decrease was greater in colder climates when expressed on a life cycle basis. The effect of residue harvest on soil N 2O emissions varied with N addition and climate. With N addition, N 2O emissions always increased, but the increase was greater in colder climates. Without N addition, N 2O emissions increased in Iowa, but decreased in Maryland and North Carolina with crop residue harvest. Although SOC was lower with residue harvest when HLFB was used for power production instead of being applied to land, the avoidance of fossil fuel emissions to the atmosphere by utilizing the cellulose and hemicellulose fractions of crop residue to produce ethanol (offsets) reduced the overall greenhouse gas (GHG) emissions because most of this residue carbon would normally be lost during microbial respiration. Losses of SOC and reduced N mineralization could both be mitigated with the application of HLFB to the land. Therefore, by returning the high-lignin fraction of crop residue to the land after production of ethanol at the biorefinery, soil carbon levels could be maintained along with the functional benefit of increased mineralized N, and more GHG emissions could be offset compared to leaving the crop residues on the land.
  • Authors:
    • Daigh,A. L.
    • Sauer,T.
    • Xiao,X. H.
    • Horton,R.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: Models of instantaneous soil-surface CO 2 efflux (SCE ins) are critical for understanding the potential drivers of soil C loss. Several simple SCE ins models have been reported in the literature. Our objective was to compare and validate selected soil temperature ( Ts)- and water content (theta v)-based equations for modeling SCE ins among a variety of cropping systems and land management practices. Soil-surface CO 2 effluxes were measured and modeled for grain-harvested corn ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] rotations, grain- and stover-harvested continuous corn systems with and without a cover crop, and reconstructed prairies with and without N fertilization on soils with subsurface drainage. Soil-surface CO 2 effluxes, Ts, and theta v were measured from 2008 to 2011. Models calibrated with weekly measured SCE ins, Ts, and theta v throughout the growing season produced lower root mean squared error (RMSE) than models calibrated with several weeks of hourly measured data. Model selection significantly affected SCE ins estimations, with models that use only Ts parameters having lower RMSE than models that use both Ts and theta v. However, the model that produced the lowest RMSE during validation estimated growing-season SCE that did not significantly differ from numerical integration of weekly measured SCE ins. All models had similar residual errors with autocorrelated trends at monthly, weekly, and hourly scales. Autoregressive moving average functions were able to precisely describe the temporal errors. To accurately model SCE ins and scale across time, improvement of temporal errors in Ts- and theta v-based SCE ins models is needed to obtain accurate and precise closure of C balances for managed and natural ecosystems.