• Authors:
    • Arbuckle, J. G., Jr.
    • Roesch-McNally, G.
  • Source: Journal
  • Volume: 70
  • Issue: 6
  • Year: 2015
  • Summary: Cover crops are widely viewed by the soil and water conservation community to be an effective means for reducing soil erosion and nutrient loss and increasing soil health, yet relatively few farmers have adopted the practice. Despite the widespread recognition of cover crops' benefits and increased promotional efforts, there have been very few peer-reviewed studies focused on farmer perspectives on or adoption of cover crops. This study, which analyzed data from a survey and in-depth interviews with Iowa farmers, examined the roles that perceived practice characteristics, perspectives on potential facilitating factors, and crop and livestock diversity play in cover crop adoption among Iowa farmers. As expected, perceived benefits were strongly associated with cover crop use. Measures of crop and livestock diversity were also positive predictors of adoption. In addition, farmers who endorsed strengthening of facilitating factors such as educational and technological infrastructure to support cover crop use were more likely to have adopted cover crops. Farmers who perceived higher levels of risks associated with cover crop use, on the other hand, were less likely to use them. Results suggest that research and promotional efforts should focus on both raising awareness of potential benefits and quantifying and communicating potential risks and risk abatement strategies. Helping farmers to better understand (1) the benefits of cover crops and how they can be enhanced, and (2) the potential risks and ways that they can be minimized might allow farmers to more effectively weigh the probable benefits and costs of cover crop use. The findings further suggest that farmers believe that better facilitating infrastructure, in the form of technical assistance (e.g., agricultural retailers and custom operators) and education, is needed to support the widespread adoption of cover crops.
  • Authors:
    • Joyce, B. L.
    • Baxter, H. L.
    • Cantrell, C. L.
    • Gawde, A.
    • Burkhardt, A.
    • Stewart, C. N.
    • Zheljazkov, V. D.
  • Source: Journal
  • Volume: 44
  • Issue: 6
  • Year: 2015
  • Summary: The Powder River Basin in Wyoming and Montana contains the United States' largest coal reserve. The area produces large amounts of natural gas through extraction from water-saturated coalbeds. Determining the impacts of coalbed natural gas-produced efflux water on crops is important when considering its potential use as supplemental irrigation water. We hypothesized that coalbed natural gas water, because of its high salinity and sodicity, would affect plant secondary metabolism (essential oils) and biomass accumulation. A 2-yr field study was conducted in Wyoming to investigate the effects of produced water on two traditional bioenergy feedstocks - corn ( Zea mays L.) and switchgrass ( Panicum virgatum L.) - and four novel biofuel feedstock species - spearmint ( Mentha spicata L.), Japanese cornmint ( Mentha canadensis L.), lemongrass ([ Cymbopogon flexuosus (Nees ex Steud.) J.F. Watson]), and common wormwood ( Artemisia vulgaris L.). The four nontraditional feedstock species were chosen because they contain high-value plant chemicals that can offset production costs. Essential oil content was significantly affected by coalbed natural gas water in lemongrass and spearmint. Oil content differences between two spearmint harvests in the same year indicated that there were significant changes between the growth stage of the plant and essential oil content; the first harvest averaged 0.42 g of oil per 100 g biomass while the second harvest (harvested before flowering) yielded only 0.19 g oil per 100 g dry biomass. Results indicated that produced water can be used for short-period (2 yr) irrigation of crops. However, prolonged use of untreated produced water for irrigation would likely have deleterious long-term effects on the soil and plants unless the water was treated or diluted (mixed) with good-quality water.
  • Authors:
    • Larsen, E.
    • Grossman, J.
    • Hoyt, G.
    • Line, D.
    • Osmond, D.
    • Edgell, J.
  • Source: Journal of Environmental Quality Abstract - Surface Water Quality
  • Volume: 44
  • Issue: 6
  • Year: 2015
  • Summary: Organic agricultural systems are often assumed to be more sustainable than conventional farming, yet there has been little work comparing surface water quality from organic and conventional production, especially under the same cropping sequence. Our objective was to compare nutrient and sediment losses, as well as sweet corn ( Zea mays L. var. saccharata) yield, from organic and conventional production with conventional and conservation tillage. The experiment was located in the Appalachian Mountains of North Carolina. Four treatments, replicated four times, had been in place for over 18 yr and consisted of conventional tillage (chisel plow and disk) with conventional production (CT/Conven), conservation no-till with conventional production (NT/Conven), conventional tillage with organic production (CT/Org), and conservation no-till with organic production (NT/Org). Water quality (surface flow volume; nitrogen, phosphorus, and sediment concentrations) and sweet corn yield data were collected in 2011 and 2012. Sediment and sediment-attached nutrient losses were influenced by tillage and cropping system in 2011, due to higher rainfall, and tillage in 2012. Soluble nutrients were affected by the nutrient source and rate, which are a function of the cropping system. Sweet corn marketable yields were greater in conventional systems due to high weed competition and reduced total nitrogen availability in organic treatments. When comparing treatment efficiency (yield kg ha -1/nutrient loss kg ha -1), the NT/Conven treatment had the greatest sweet corn yield per unit of nutrient and sediment loss. Other treatment ratios were similar to each other; thus, it appears the most sustainably productive treatment was NT/Conven.
  • Authors:
    • Stuedemann, J.
    • Franzluebbers, A.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 6
  • Year: 2015
  • Summary: Cover crops are a key component of conservation cropping systems. They can also be a key component of integrated crop-livestock systems by offering high-quality forage during short periods between cash crops. The impact of cattle grazing on biologically active soil carbon (C) and nitrogen (N) fractions has not received much attention. We investigated the impacts of tillage (conventional disk and no tillage) and cover crop management (ungrazed and grazed) on biologically active soil C and N fractions from biennial sampling during seven years of continuous management. Soil microbial biomass C was unaffected by cover crop management under conventional tillage, but was enhanced with grazing compared with no grazing under no tillage at a depth of 0 to 6 cm (0 to 2.4 in), as well as at 0 to 30 cm (0 to 12 in). The same effect occurred for the flush of carbon dioxide (CO2) following rewetting of dried soil during 3 days of incubation at a depth of 0 to 6 cm only, while it occurred for cumulative C mineralization during 24 days of incubation at a depth of 0 to 30 cm only. Grazing effects on net N mineralization during 24 days of incubation and residual soil inorganic N were nonexistent. All biologically active fractions of soil C and N were highly stratified with depth under no tillage and less so under conventional tillage. Cumulative stocks of soil C and N fractions to a depth of 0 to 30 cm were generally not significantly different between cover crop management systems, nor between tillage systems, except for (1) lower soil microbial biomass C with than without grazing under conventional tillage, (2) greater soil microbial biomass C with than without grazing under no tillage, and (3) lower cumulative C mineralization during 24 days under no tillage than under conventional tillage. Grazing of cover crops can be recommended as a strategy to promote greater adoption of cover cropping throughout the southeastern United States.
  • Authors:
    • Robertson, G.
    • Tang, J.
    • Cui, M.
    • Gelfand, I.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 212
  • Issue: December 2015
  • Year: 2015
  • Summary: Climate change is causing the intensification of both rainfall and droughts in temperate climatic zones, which will affect soil drying and rewetting cycles and associated processes such as soil greenhouse gas (GHG) fluxes. We investigated the effect of soil rewetting following a prolonged natural drought on soil emissions of nitrous oxide (N 2O) and carbon dioxide (CO 2) in an agricultural field recently converted from 22 years in the USDA Conservation Reserve Program (CRP). We compared responses to those in a similarly managed field with no CRP history and to a CRP reference field. We additionally compared soil GHG emissions measured by static flux chambers with off-site laboratory analysis versus in situ analysis using a portable quantum cascade laser and infrared gas analyzer. Under growing season drought conditions, average soil N 2O fluxes ranged between 0.2 and 0.8 g N m -2 min -1 and were higher in former CRP soils and unaffected by nitrogen (N) fertilization. After 18 days of drought, a 50 mm rewetting event increased N 2O fluxes by 34 and 24 fold respectively in the former CRP and non-CRP soils. Average soil CO 2 emissions during drought ranged from 1.1 to 3.1 mg C m -2 min -1 for the three systems. CO 2 emissions increased ~2 fold after the rewetting and were higher from soils with higher C contents. Observations are consistent with the hypothesis that during drought soil N 2O emissions are controlled by available C and following rewetting additionally influenced by N availability, whereas soil CO 2 emissions are independent of short-term N availability. Finally, soil GHG emissions estimated by off-site and in situ methods were statistically identical.
  • Authors:
    • Cisz, M.
    • Galdos, M.
    • Hilbert, J.
    • Rod, K.
    • Ferreira, A.
    • Leite, L.
    • Kaczmarek, D.
    • Chimner, R.
    • Resh, S.
    • Asbjornsen, H.
    • Scott, D.
    • Titus, B.
    • Gollany, H.
  • Source: Environmental Management
  • Volume: 56
  • Issue: 6
  • Year: 2015
  • Summary: Rapid expansion in biomass production for biofuels and bioenergy in the Americas is increasing demand on the ecosystem resources required to sustain soil and site productivity. We review the current state of knowledge and highlight gaps in research on biogeochemical processes and ecosystem sustainability related to biomass production. Biomass production systems incrementally remove greater quantities of organic matter, which in turn affects soil organic matter and associated carbon and nutrient storage (and hence long-term soil productivity) and off-site impacts. While these consequences have been extensively studied for some crops and sites, the ongoing and impending impacts of biomass removal require management strategies for ensuring that soil properties and functions are sustained for all combinations of crops, soils, sites, climates, and management systems, and that impacts of biomass management (including off-site impacts) are environmentally acceptable. In a changing global environment, knowledge of cumulative impacts will also become increasingly important. Long-term experiments are essential for key crops, soils, and management systems because short-term results do not necessarily reflect long-term impacts, although improved modeling capability may help to predict these impacts. Identification and validation of soil sustainability indicators for both site prescriptions and spatial applications would better inform commercial and policy decisions. In an increasingly inter-related but constrained global context, researchers should engage across inter-disciplinary, inter-agency, and international lines to better ensure the long-term soil productivity across a range of scales, from site to landscape.
  • Authors:
    • Franzluebbers, A. J.
    • Stuedemann, J. A.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 4
  • Year: 2014
  • Summary: Soil organic C and N are important indicators of agricultural sustainability, yet numerous field studies have revealed a multitude of responses in the extent and rate of change imposed by conservation management and, therefore, a lack of clarity on responses. We conducted an evaluation of total and particulate organic C and N in the surface 30 cm on a Typic Kanhapludult in northern Georgia during 7 yr of tillage (conventional disk and no tillage) and cover crop utilization (ungrazed and grazed by cattle). Soil organic C and total soil N were greater under no tillage (NT) than under conventional tillage (CT) at depths of 0 to 3 and 3 to 6 cm but were lower under NT than CT at depths of 12 to 20 and 20 to 30 cm. Total soil N accumulated with time at a depth of 0 to 6 cm under both tillage systems and the rate tended to be greater under NT than under CT (0.039 vs. 0.021 Mg N ha-1 yr -1, p = 0.10). Soil organic C accumulated with time at a depth of 0 to 6 cm under all management systems, but there was a significant tillage × cover crop interaction (0.68 and 1.09 Mg C ha-1 yr -1 with ungrazed cover crop management under CT and NT, respectively, and 0.84 and 0.66 Mg C ha-1 yr-1 with grazed cover crop management under CT and NT, respectively). At a depth of 0 to 30 cm, there was only a tillage trend (1.00 and 1.59 Mg C ha-1 yr-1 under CT and NT, respectively; p = 0.09). Particulate organic C was more dramatically different than soil organic C between tillage regimes at a depth of 0 to 30 cm (-0.49 and 0.35 Mg C ha-1 yr-1 under CT and NT, respectively; p < 0.001). Grazing of cover crops had little negative impact on soil C and N fractions, suggesting that NT and grazing of cover crops could provide a broader-spectrum conservation cropping approach in the southeastern United States. © Soil Science Society of America, 5585 Guilford Rd.
  • Authors:
    • Sadler, E. J.
    • Tomer, M. D.
    • Shields, F. Douglas, Jr.
    • Nearing, M. A.
    • Garbrecht, J. D.
    • Bonta, J. V.
    • Baffaut, C.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 5
  • Year: 2014
  • Summary: Selected watershed studies of the Conservation Effects Assessment Project (CEAP) are reviewed and findings are interpreted from the perspective of potential conservation outcomes due to climate change scenarios. Primary foci are runoff, soil erosion, sediment transport, and watershed sediment yield. Highlights, successes, and challenges with regards to climate change impacts on soil erosion, runoff, and watershed sediment yield are presented. The covered information adds to the existing knowledge base of climate change impacts and provides another piece of information that may be useful in the planning and management of agricultural watersheds; assessment of conservation needs; and development, funding, and implementation of conservation programs. The selected conservation assessment studies include, among others, a thought experiment on the sensitivity of soil erosion, runoff, and sediment yield to changes in rainfall; a computer-based investigation of potential climate change effects on runoff and soil erosion in a southeastern Arizona rangeland; the complex response of northern Mississippi watersheds to runoff variations and channel stabilization measures; the impact of conservation practices and a persistent pluvial period on watershed runoff and sediment yield in Oklahoma; and stream bank erosion during major flooding in Iowa and river corridor management. A study of rainfall-runoff in an north-central Missouri watershed and a curve number analysis in a northern Appalachian experimental watershed are included herein. Findings showed that climate change scenarios of increased precipitation intensity lead to an exponential increase in soil erosion, runoff, and watershed sediment yield, thereby stressing current conservation practices or future practices designed with present day practice standards. This diminishes conservation practice effectiveness and increases sediment supply to the stream network. The sensitive response of the watershed hydrologic system may lead to renewed soil erosion that is large enough to offset the reduction in soil loss achieved by current conservation practices. However, in alluvial-floodplain environments with non-cohesive bed and bank material, watershed sediment yield is controlled by channel discharge and energy slope, neither of which is influenced by traditional in-field conservation practices or channel bank stabilization structures. Thus, control of sediment yield will gradually shift in the downstream direction from sediment supply to sediment transport capacity and blur any existing relation between a climate change signal, in-field conservation outcomes, and sediment yield at watershed outlets. Targeting conservation practices to erosion prone areas, expanding conservation coverage, and adapting agronomic practices may be necessary to prevent excessive soil erosion and downstream sedimentation under climate change scenarios that include intensified precipitation.
  • Authors:
    • Kremer, R. J.
    • Cambardella, C. A.
    • Stott, D. E.
    • Karlen, D. L.
    • King, K. W.
    • McCarty, G. W.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 5
  • Year: 2014
  • Summary: Soil quality (SQ) assessment is a proactive process for evaluating soil and crop management effects on biological, chemical, and physical indicators of soil health. Our objectives were to evaluate several SQ indicators within five Agricultural Research Service (ARS) experimental watersheds (WS) and determine if those indicators were affected by manure, tillage, or crop rotation histories. Ten soil quality indicators were measured within each of 600 0 to 5 cm (0 to 2 in) depth and 398 5 to 15 cm (2 to 6 in) depth increment samples, evaluated statistically, and then scored using the Soil Management Assessment Framework. Except for soil organic carbon (C) at both depth increments or microbial biomass C and beta-glucosidase within the 5 to 15 cm increment, the indicators showed significant WS differences. Except for surface soil-test phosphorous (P), Soil Management Assessment Framework indicator scores and overall soil quality index values also showed significant (p <= 0.05) WS differences. Microbial biomass C was significantly affected by crop rotation at both sampling depths and by WS within the surface 5 cm. beta-glucosidase was significantly affected by all four factors (WS, manure, tillage, and crop rotation) and their interactions within the 0 to 5 cm increment. The water-stable macroaggregate indictor within the 0 to 5 cm increment and within the 5 to 15 cm increment, however, were not significantly different for the tillage and manure application treatments, respectively. Our study showed that the ARS Conservation Effects Assessment Project (CEAP) watersheds provided a moderately controlled example that watershed-scale monitoring of soil quality is feasible and should be used to monitor soil health and/or conservation program effectiveness.
  • Authors:
    • Palik, B. J.
    • D'Amato, A. W.
    • Kurth, V. J.
    • Bradford, J. B.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 2
  • Year: 2014
  • Summary: The substitution of forest-derived woody biofuels for fossil fuel energy has garnered increasing attention in recent years, but information regarding the mid- and long-term effects on soil productivity is limited. We investigated 15-yr temporal trends in forest floor and mineral soil (0-30 cm) C and N pools in response to organic matter removal treatments (OMR; stem-only harvest, SOH; whole-tree harvest, WTH; and whole-tree plus forest floor removal, FFR) at three edaphically distinct aspen (Populus tremuloides Michx. and P. grandidentata Michx.) forests in the Great Lakes region. The OMR and temporal effects were generally site specific, and both were most evident in the forest floor and combined profile (mineral soil and forest floor) compared with the mineral soil alone. Forest floor and combined profile C and N pools were generally similar in the SOH and WTH treatments, suggesting that slash retention has little impact on soil C and N in this time frame. Temporal changes in C and N at one of the three sites were consistent with patterns documented following exotic earthworm invasion, but mineral soil pools at the other two sites were stable over time. Power analyses demonstrated that significant effects were more likely to be detected for temporal differences than the effects of OMR and in the combined profile than in the mineral soil. Our findings are consistent with previous work demonstrating that OMR effects on soil C and N pools are site specific and more apparent in the forest floor than the mineral soil. © Soil Science Society of America.