• Authors:
    • Stevenson, F. C.
    • Vanasse, A.
    • Legere, A.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 3
  • Year: 2013
  • Summary: Combining low-input systems with conservation tillage may be feasible for field crops under northeastern conditions. This study compared the effects of herbicide-free (HF), organic (ORG), conventional (CONV), and herbicide-tolerant (GM) cropping systems applied to three 20 yr-old tillage treatments (MP, moldboard plow; CP, chisel plow; NT, no-till) on weed biomass and crop productivity in a 4-yr barley ( Hordeum vulgare L.)-red clover ( Trifolium pratense L.)-corn ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] rotation. Barley yield (4.5 Mg ha -1), and red clover forage yield (two cuts: 5.3 Mg ha -1) were similar across treatments. With MP and CP tillage, silage corn yield for CONV and GM systems (15 Mg ha -1) was 25% greater than for HF and ORG (11 Mg ha -1), whereas HF-NT and ORG-NT systems produced no harvestable yield. Soybean yield for HF-MP and ORG-MP systems was similar to that for CONV and GM (2.4 Mg ha -1), whereas yield in for the HF and ORG systems with CP and NT was half or less than for other treatments. Some form of primary tillage (CP or MP) was needed in corn and soybean to achieve adequate weed control and yield in the ORG and HF systems. Midseason weed proportion of total biomass was greater in the HF and ORG systems with CP and NT, and provided good yield prediction in corn ( R2=0.74) and soybean ( R2=0.84). Nutrient availability appeared adequate in corn following N 2-fixing red clover but limiting in NT and CP for soybean following corn. Improving crop sequence, fertilization, and weed management will be key to the adoption of low-input systems using conservation tillage practices in cool, humid climates.
  • Authors:
    • Ndabamenye, T.
    • Lelei, D.
    • Koala, S.
    • Hurisso, T. T.
    • Hoogmoed, M.
    • Gassner, A.
    • Ayuke, F.
    • Vanlauwe, B.
    • Paul, B. K.
    • Six, J.
    • Pulleman, M. M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 164
  • Year: 2013
  • Summary: Conservation agriculture is widely promoted for soil conservation and crop productivity increase, although rigorous empirical evidence from sub-Saharan Africa is still limited. This study aimed to quantify the medium-term impact of tillage (conventional and reduced) and crop residue management (retention and removal) on soil and crop performance in a maize-soybean rotation. A replicated field trial was started in sub-humid Western Kenya in 2003, and measurements were taken from 2005 to 2008. Conventional tillage negatively affected soil aggregate stability when compared to reduced tillage, as indicated by lower mean weight diameter values upon wet sieving at 0-15 cm ( PT<0.001). This suggests increased susceptibility to slaking and soil erosion. Tillage and residue management alone did not affect soil C contents after 11 cropping seasons, but when residue was incorporated by tillage, soil C was higher at 15-30 cm ( PT*R=0.037). Lack of treatment effects on the C content of different aggregate fractions indicated that reduced tillage and/or residue retention did not increase physical C protection. The weak residue effect on aggregate stability and soil C may be attributed to insufficient residue retention. Soybean grain yields tended to be suppressed under reduced tillage without residue retention, especially in wet seasons ( PT*R=0.070). Consequently, future research should establish, for different climatic zones and soil types, the critical minimum residue retention levels for soil conservation and crop productivity.
  • Authors:
    • Pijanowski, B. C.
    • Plourde, J. D.
    • Pekin, B. K.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 165
  • Year: 2013
  • Summary: While crop rotation patterns can be complex with multiple crops rotated over several years, the most common rotation practice in the Central United States is biannual rotation between corn and soybeans. We analyzed the changes in crop rotation patterns from 2003 to 2010 using the Cropland Data Layer (CDL), which provides remotely sensed land cover layers for agricultural crops in the Central United States. The accuracy of the CDL was validated by comparing the total acreage for a state or county present in the CDL with the total planted crop acreage available from the National Agricultural Statistics Service. The data layers were combined into two time periods 2003-2006 and 2007-2010, and specific rotation patterns were determined for every location in the study area. The combinations resulted in unique sequences such as single, double, triple and quadruple, the latter of which is equivalent to the same crop class present all four years at a particular location. Corn and soybeans were analyzed to determine the amount of area used for production as well as the amount of change between unique crop rotation sequences. While the total area under production of major crops in the second half of our study period increased only slightly, the extent to which major crops (e.g., corn and soybeans) were grown in continuous cropping sequences increased significantly. For example, the amount of land impacted by corn in the first time period increased by only 2% in the second time period. However, the amount of corn grown in quadruple sequence doubled from the first half to the second half of our study period. We conclude that, although crop rotation patterns are very complex in this region, involving considerable amount of non-cropland, the footprint of major crops such as corn have moved toward monoculture cropping practices in the last decade.
  • Authors:
    • Uliasz, M.
    • Richardson, S.
    • Miles, N.
    • Davis, K. J.
    • Denning, A. S.
    • West, T. O.
    • Lauvaux, T.
    • Schuh, A. E.
    • Lokupitiya, E.
    • Cooley, D.
    • Andrews, A.
    • Ogle, S.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 5
  • Year: 2013
  • Summary: An intensive regional research campaign was conducted by the North American Carbon Program (NACP) in 2007 to study the carbon cycle of the highly productive agricultural regions of the Midwestern United States. Forty-five different associated projects were conducted across five US agencies over the course of nearly a decade involving hundreds of researchers. One of the primary objectives of the intensive campaign was to investigate the ability of atmospheric inversion techniques to use highly calibrated CO 2 mixing ratio data to estimate CO 2 flux over the major croplands of the United States by comparing the results to an inventory of CO 2 fluxes. Statistics from densely monitored crop production, consisting primarily of corn and soybeans, provided the backbone of a well studied bottom-up inventory flux estimate that was used to evaluate the atmospheric inversion results. Estimates were compared to the inventory from three different inversion systems, representing spatial scales varying from high resolution mesoscale (PSU), to continental (CSU) and global (CarbonTracker), coupled to different transport models and optimization techniques. The inversion-based mean CO 2-C sink estimates were generally slightly larger, 8-20% for PSU, 10-20% for CSU, and 21% for CarbonTracker, but statistically indistinguishable, from the inventory estimate of 135 TgC. While the comparisons show that the MCI region-wide C sink is robust across inversion system and spatial scale, only the continental and mesoscale inversions were able to reproduce the spatial patterns within the region. In general, the results demonstrate that inversions can recover CO 2 fluxes at sub-regional scales with a relatively high density of CO 2 observations and adequate information on atmospheric transport in the region.
  • Authors:
    • Anderson-Teixeira, K. J.
    • Masters, M. D.
    • Mitchell, C. A.
    • David, M. B.
    • Smith, C. M.
    • Bernacchi, C. J.
    • DeLucia, E. H.
  • Source: Journal of Environmental Quality
  • Volume: 42
  • Issue: 1
  • Year: 2013
  • Summary: Current biofuel feedstock crops such as corn lead to large environmental losses of N through nitrate leaching and N 2O emissions; second-generation cellulosic crops have the potential to reduce these N losses. We measured N losses and cycling in establishing miscanthus ( Miscanthus * giganteus), switchgrass ( Panicum virgatum L. fertilized with 56 kg N ha -1 yr -1), and mixed prairie, along with a corn ( Zea mays L.)-corn-soybean [ Glycine max (L.) Merr.] rotation (corn fertilized at 168-202 kg N ha -1). Nitrous oxide emissions, soil N mineralization, mid-profile nitrate leaching, and tile flow and nitrate concentrations were measured. Perennial crops quickly reduced nitrate leaching at a 50-cm soil depth as well as concentrations and loads from the tile systems (year 1 tile nitrate concentrations of 10-15 mg N L -1 declined significantly by year 4 in all perennial crops to <0.6 mg N L -1, with losses of <0.8 kg N ha -1 yr -1). Nitrous oxide emissions were 2.2 to 7.7 kg N ha -1 yr -1 in the corn-corn-soybean rotation but were <1.0 kg N ha -1 yr -1 by year 4 in the perennial crops. Overall N balances (atmospheric deposition+fertilization+soybean N 2 fixation-harvest, leaching losses, and N 2O emissions) were positive for corn and soybean (22 kg N ha -1 yr -1) as well as switchgrass (9.7 kg N ha -1 yr -1) but were -18 and -29 kg N ha -1 yr -1 for prairie and miscanthus, respectively. Our results demonstrate rapid tightening of the N cycle as perennial biofuel crops established on a rich Mollisol soil.
  • Authors:
    • McConnaughay, K. D.
    • Bernacchi, C. J.
    • Richter, K. T.
    • Bryant, J. J.
    • Twine, T. E.
    • Morris, S. J.
    • Leakey, A. D. B.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 9
  • Year: 2013
  • Summary: The physiological response of vegetation to increasing atmospheric carbon dioxide concentration ([CO 2]) modifies productivity and surface energy and water fluxes. Quantifying this response is required for assessments of future climate change. Many global climate models account for this response; however, significant uncertainty remains in model simulations of this vegetation response and its impacts. Data from in situ field experiments provide evidence that previous modeling studies may have overestimated the increase in productivity at elevated [CO 2], and the impact on large-scale water cycling is largely unknown. We parameterized the Agro-IBIS dynamic global vegetation model with observations from the SoyFACE experiment to simulate the response of soybean and maize to an increase in [CO 2] from 375 ppm to 550 ppm. The two key model parameters that were found to vary with [CO 2] were the maximum carboxylation rate of photosynthesis and specific leaf area. Tests of the model that used SoyFACE parameter values showed a good fit to site-level data for all variables except latent heat flux over soybean and sensible heat flux over both crops. Simulations driven with historic climate data over the central USA showed that increased [CO 2] resulted in decreased latent heat flux and increased sensible heat flux from both crops when averaged over 30 years. Thirty-year average soybean yield increased everywhere (ca. 10%); however, there was no increase in maize yield except during dry years. Without accounting for CO 2 effects on the maximum carboxylation rate of photosynthesis and specific leaf area, soybean simulations at 550 ppm overestimated leaf area and yield. Our results highlight important model parameter values that, if not modified in other models, could result in biases when projecting future crop-climate-water relationships.
  • Authors:
    • Franzluebbers, A. J.
    • Andrews, S. S.
    • Kome, C. E.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 68
  • Issue: 4
  • Year: 2013
  • Summary: Simple, yet reliable models are needed to quantify soil organic carbon (SOC) changes for the wide diversity of agricultural management conditions in the United States. We compared the outputs of two relatively simple models currently available for farmers and government-financed farm support agencies: the Carbon (C) Management Evaluation Tool for Voluntary Reporting of Greenhouse Gases (COMET-VR) and the Soil Conditioning Index (SCI). Simulations were conducted for 18 locations throughout the United States for five soil textural regimes (loamy sand, sandy loam, silt loam, clay loam, and silty clay loam), three tillage management systems (conventional tillage [CT], minimum tillage [MT], and no tillage [NT]), and two crop rotations (wheat [Triticum aestivum L.]-potato [Solanum tuberosum L.] and wheat-four-year alfalfa [Medicago sativa L.] in western states and corn [Zea mays L.]-soybean [Glycine max L.] and corn-soybean-wheat in eastern states). Both models ranked SOC change as NT > MT > CT, whereby SOC change decreased with increasing soil disturbance with tillage However, models were divergent with regards to soil texture; SOC change was greater in coarse-textured than in fine-textured soils with COMET-VR, but SOC change was lower in coarse-textured than in fine-textured soils with SCI. For crop rotations, SOC change was greater or equal in simpler than in more complex rotation with COMET-VR, but smaller in simpler than in more complex rotations with SCI. Overall, SOC sequestration predicted by COMET-VR was positively related to SCI score, especially when accounting for differences in environmental conditions of a location. Our results suggest that both Models have value and limitations and that measures of SOC sequestration are predictable with these tools under a diversity of typical management conditions in the United States.
  • Authors:
    • Yashima, M.
    • Zsuposne Olah, A.
    • Vago, I.
    • Katai, J.
    • Nagano, H.
    • Kong, Y.
    • Inubushi, K.
  • Source: Soil Science and Plant Nutrition
  • Volume: 59
  • Issue: 3
  • Year: 2013
  • Summary: The production/consumption of greenhouse gases (GHG) in soils are of great importance in global warming, but the involved soil physico-chemical and biological characteristics affecting GHG production and consumption potentials are poorly understood in different land-use types. Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) production/consumption potentials from four land-use types and 10 soil types in central Japan and eastern Hungary, and their relationships with soil characteristics, were investigated. The average of CO2 production in Japanese soils was significantly higher than that of Hungarian soils due to the relatively higher microbial biomass carbon (MBC) content. N2O production from both countries' soils did not exhibit a significant difference. Most soils except Japanese paddy and soybean soils showed the potentials for CH4 consumption. Forest and grassland soils had relatively higher CO2 and N2O production than orchard and cropland soils for both countries. From regression analyses, it could be concluded that soil total nitrogen (TN) and ammonium-nitrogen (NH4 (+)-N) account for 40.8% and 25.5% variations of the soils' CO2 and N2O productions, respectively. The CH4 consumption was positively correlated with soil carbon/nitrogen (C/N) ratio, while soil MBC availability could account for 15% variation of CH4 consumption under aerobic conditions.
  • Authors:
    • Mousavi-Avval, S. H.
    • Keyhani, A.
    • Knudsen, M. T.
    • Dalgaard, T.
    • Jafari, A.
    • Rafiee, S.
    • Mohammadi, A.
    • Hermansen, J. E.
  • Source: Journal of Cleaner Production
  • Volume: 54
  • Year: 2013
  • Summary: Joint implementation of Life Cyc00le Assessment (LCA) and Data Envelopment Analysis (DEA) has recently showed to be a suitable tool for measuring efficiency in agri-food systems. In the present study, LCA + DEA methodologies were applied for a total of 94 soybean farms in Iran to benchmark the level of operational input efficiency of each farmer. Likewise, potential reductions in the consumption levels of the physical inputs were determined, while estimating the environmental improvements linked to these reduction targets. Our results indicate that 46% of the farms studied operated efficient. The estimated Global Warming Potential (GWP) reduction for the whole sample was obtained similar to 11% according to DEA model results. Among the field operations, the contribution of irrigation to the total GWP reduction was the highest (63%) followed by fertilization (34%). The results also revealed that farms which burnt crop residue in the field generate significantly more greenhouse gas emissions than other farms. The raising of operational input efficiency and limiting of crop residue burning in the field are recommended options to ensure more environmental friendly soybean farming systems in the region. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Gottschall, N.
    • Drury, C. F.
    • Gregorich, E. G.
    • Topp, E.
    • Sunohara, M. D.
    • Nangia, V.
    • Lapen, D. R.
  • Source: Journal of Environmental Management
  • Volume: 129
  • Year: 2013
  • Summary: Controlled tile drainage can boost crop yields and improve water quality, but it also has the potential to increase GHG emissions. This study compared in-situ chamber-based measures of soil CH4, N2O, and CO2 fluxes for silt loam soil under corn and soybean cropping with conventional tile drainage (UTD) and controlled tile drainage (LID). A semi-empirical model (NEMIS-NOE) was also used to predict soil N2O fluxes from soils using observed soil data. Observed N2O and CH4 fluxes between UTD and CID fields during the farming season were not significantly different at 0.05 level. Soils were primarily a sink for CH4 but in some cases a source (sources were associated exclusively with CTD). The average N2O fluxes measured ranged between 0.003 and 0.028 kg N ha(-1) day(-1). There were some significantly higher (p <= 0.05) CO2 fluxes associated with LID relative to UTD during some years of study. Correlation analyses indicated that the shallower the water table, the greater the CO2 fluxes. Higher corn plant C for CTD tended to offset estimated higher CTD CO2 C losses via soil respiration by similar to 100-300 kg C ha(-1). There were good fits between observed and predicted (NEMIS-NOE) N2O fluxes for corn (R-2 = 0.70) and soybean (R-2 = 0.53). Predicted N2O fluxes were higher for CID for approximately 70% of the paired-field study periods suggesting that soil physical factors, such as water-filled pore space, imposed by CTD have potentially strong impacts on net N fluxes. Model predictions of daily cumulative N2O fluxes for the agronomically-active study period for corn-CTD and corn-UTD, as a percentage of total N fertilizer applied, were 3.1% and 2.6%, respectively. For predicted N2O fluxes on basis of yield units, indices were 0.0005 and 0.0004 (kg N kg(-1) crop grain yield) for CTD and UTD corn fields, respectively, and 0.0011 and 0.0005 for CTD and UTD soybean fields, respectively.