• Authors:
    • Siebers,M. H.
    • Yendrek,C. R.
    • Drag,D.
    • Locke,A. M.
    • Acosta,L. R.
    • Leakey,A. D. B.
    • Ainsworth,E. A.
    • Bernacchi,C. J.
    • Ort,D. R.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: Heat waves already have a large impact on crops and are predicted to become more intense and more frequent in the future. In this study, heat waves were imposed on soybean using infrared heating technology in a fully open-air field experiment. Five separate heat waves were applied to field-grown soybean ( Glycine max) in central Illinois, three in 2010 and two in 2011. Thirty years of historical weather data from Illinois were analyzed to determine the length and intensity of a regionally realistic heat wave resulting in experimental heat wave treatments during which day and night canopy temperatures were elevated 6°C above ambient for 3 days. Heat waves were applied during early or late reproductive stages to determine whether and when heat waves had an impact on carbon metabolism and seed yield. By the third day of each heat wave, net photosynthesis ( A), specific leaf weight (SLW), and leaf total nonstructural carbohydrate concentration (TNC) were decreased, while leaf oxidative stress was increased. However, A, SLW, TNC, and measures of oxidative stress were no different than the control ca. 12 h after the heat waves ended, indicating rapid physiological recovery from the high-temperature stress. That end of season seed yield was reduced (~10%) only when heat waves were applied during early pod developmental stages indicates the yield loss had more to do with direct impacts of the heat waves on reproductive process than on photosynthesis. Soybean was unable to mitigate yield loss after heat waves given during late reproductive stages. This study shows that short high-temperature stress events that reduce photosynthesis and increase oxidative stress resulted in significant losses to soybean production in the Midwest, U.S. The study also suggests that to mitigate heat wave-induced yield loss, soybean needs improved reproductive and photosynthetic tolerance to high but increasingly common temperatures.
  • Authors:
    • Sieverding,H. L.
    • Bailey,L. M.
    • Hengen,T. J.
    • Clay,D. E.
    • Stone,J. J.
  • Source: Journal of Environmental Quality
  • Volume: 44
  • Issue: 4
  • Year: 2015
  • Summary: Biofuel policy changes in the United States have renewed interest in soybean [ Glycine max (L.) Merr.] biodiesel. Past studies with varying methodologies and functional units can provide valuable information for future work. A meta-analysis of nine peer-reviewed soybean life cycle analysis (LCA) biodiesel studies was conducted on the northern Great Plains in the United States. Results of LCA studies were assimilated into a standardized system boundary and functional units for global warming (GWP), eutrophication (EP), and acidification (AP) potentials using biodiesel conversions from peer-reviewed and government documents. Factors not fully standardized included variations in N 2O accounting, mid- or end-point impacts, land use change, allocation, and statistical sampling pools. A state-by-state comparison of GWP lower and higher heating values (LHV, HHV) showed differences attributable to variations in spatial sampling and agricultural practices (e.g., tillage, irrigation). The mean GWP of LHV was 21.1 g.CO 2-eq MJ -1 including outliers, and median EP LHV and AP LHV was 0.019 g.PO 4-eq MJ -1 and 0.17 g.SO 2-eq MJ -1, respectively, using the limited data available. An LCA case study of South Dakota soybean-based biodiesel production resulted in GWP estimates (29 or 31 g.CO 2-eq MJ -1; 100% mono alkyl esters [first generation] biodiesel or 100% fatty acid methyl ester [second generation] biodiesel) similar to meta-analysis results (30.1 g.CO 2-eq MJ -1). Meta-analysis mean results, including outliers, resemble the California Low Carbon Fuel Standard for soybean biodiesel default value without land use change of 21.25 g.CO 2-eq MJ -1. Results were influenced by resource investment differences in water, fertilizer (e.g., type, application), and tillage. Future biofuel LCA studies should include these important factors to better define reasonable energy variations in regional agricultural management practices.
  • Authors:
    • Steenwerth,K. L.
    • Strong,E. B.
    • Greenhut,R. F.
    • Williams,L.
    • Kendall,A.
  • Source: The International Journal of Life Cycle Assessment
  • Volume: 20
  • Issue: 9
  • Year: 2015
  • Summary: Purpose: This study assesses life cycle greenhouse gas (GHG) emissions, energy use, and freshwater use in wine grape production across common vineyard management scenarios in two representative growing regions (Napa and Lodi) of the US state of California. California hosts 90 % of US grape growing area, and demand for GHG emissions estimates of crops has increased due to consumer interest and policies such as California’s Global Warming Solutions Act. Methods: The study’s scope includes the annual cycle for wine grape production, beginning at raw material extraction for production of vineyard inputs and ending at delivery of wine grapes to the winery gate, and excludes capital infrastructure. Two hundred forty production scenarios were modeled based on data collected from land owners, vineyard managers, and third-party vineyard management companies. Thirty additional in-person interviews with growers throughout Napa and Lodi were also conducted to identify the diversity of farming practices, site characteristics, and yields (among other factors) across 90 vineyards. These vineyards represent a cross-section of the regional variability in soil, climate, and landscape used for wine grape production. Results and discussion: Energy use and global warming potential (GWP) per metric ton (t) across all 240 production scenarios range between 1669 and 8567 MJ and 87 and 548 kg CO2e. Twelve scenarios were selected for closer inspection to facilitate comparison of the two regions and grower practices. Comparison by region shows energy use, GWP, and water use for typical practices were more than twice as great in Napa (6529 MJ/t, 456 kg CO2e/t, and 265 m3 H2O/t) than Lodi (2759 MJ/t, 203 kg CO2e/t, and 141 m3 H2O/t), but approximately 16 % greater on a per hectare basis. Hand harvest (versus mechanical harvesting) and frost protection processes in Napa contributed to higher values per hectare, and lower yields in Napa account for the even larger difference per metric ton. Hand harvesting and lower yields reflect the higher value of Napa wine grapes. Conclusions: The findings underscore the regional distinctions in wine grape production, which include different management goals, soils, and climate. When vineyards are managed for lower yields, as they are in Napa, energy, water, and GWP will likely be higher on a per mass basis. Strategies to reduce emissions in these regions cannot rely on increasing yields (a common approach), and alternative strategies are required, for example developing high-value co-products. © 2015 Springer-Verlag Berlin Heidelberg
  • Authors:
    • Thapa,R.
    • Chatterjee,A.
    • Johnson,J. M. F.
    • Awale,R.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Nitrogen losses associated with fertilizer application have negative economic and environmental consequences, but urease and nitrification inhibitors have potential to reduce N losses. The effectiveness of these inhibitors has been studied extensively in irrigated but not in rainfed systems. This study was conducted at Glyndon, MN, under rainfed conditions to assess the impact of urease and nitrification inhibitors on NH 3 volatilization, N 2O emissions, and NO 3- concentrations below the spring wheat ( Triticum aestivum L.) rooting zone. Urea (U), urea with urease and nitrification inhibitors (SU), and urea with nitrification inhibitor only (UI) were applied at 146 and 168 kg N ha -1 along with the control treatments. Cumulative NH 3 volatilization was reduced by 26%, N 2O emissions measured 18 d after planting were reduced by 50% with SU, but no significant reduction was observed with UI compared to U. We did not observe a significant effect of higher N rate on N 2O emissions, but lower N application rate (146 kg N ha -1) significantly reduced NH 3 volatilization by 26% compared to 168 kg N ha -1. Nitrate concentration below the rooting zone was reduced by applying N at lower rate and also through the use of SU and UI instead of U. Soil inorganic N intensity was significantly related with cumulative N 2O emissions. Nitrogen source and rate did not influence grain yield and protein content. This single-growing season study under rainfed conditions suggests that fertilizer N-stabilizers can be successfully used to minimize N losses without compromising grain yield and protein content.
  • Authors:
    • van Dijl,E. A.
    • Grogan,K. A.
    • Borisova,T.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 4
  • Year: 2015
  • Summary: In the United States, Florida ranks second among states for both value and land area of vegetable production, but this production is affected by periodic droughts. Florida has experienced at least one severe and widespread drought every decade since 1900, and climate change projections show that meteorological droughts will occur more often in the future. While drought and climate change affect the supply side, population growth is expected to affect the demand side of water availability. Given these threats to future water availability, the adoption of drought adaptation and water conservation measures is of increasing importance in Florida. Using a 2013 survey of Florida vegetable growers, this paper addresses two main components of this problem. First, we assess the current rates of adoption of drought adaptation measures. Second, we analyze which factors influence or impede the adoption of these measures to provide policy recommendations to increase adoption in the future. We find low rates of adoption of adaptations, ranging from 13% to 55%, and factors determining who adopts a given adaptation vary by adaptation. Factors can have opposite effects on the probability of adoption across different adaptations. Unlike most previous work, we find that growers with more education have lower rates of adoption of water augmentation measures, and lack of land ownership does not necessarily impede adoption of adaptations with large initial investment.
  • Authors:
    • Veenstra,J. J.
    • Burras,C. L.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 4
  • Year: 2015
  • Summary: Despite a large body of scientific research that shows that soils change on relatively short time scales under different management regimes, classical pedological theory states that we should expect these changes to occur only in the surface few centimeters and that they are not of adequate magnitude to suggest fundamental changes in pedon character over short periods of time. In fact, rarely, do the scientists that make these comparisons report on any properties deeper than 30 to 45 cm in the soil profile. With this study, we evaluate soil transformation to a depth of 150 cm after 50 yr of intensive row-crop agricultural land use in a temperate, humid, continental climate (Iowa, United States), by resampling sites that were initially described by the United States soil survey between 1943 and 1963. We find that, through agricultural land use, humans are accelerating soil formation and transformation to a depth of 100 cm or more by accelerating erosion, sedimentation, acidification, and mineral weathering, and degrading soil structure, while deepening dark-colored, organic-matter rich surface horizons, translocating and accumulating organic matter deeper in the soil profile and lowering the water table. Some of these changes can be considered positive improvements, but many of these changes may have negative effects on the soils' future productive capacity. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All rights reserved.
  • Authors:
    • Veum,K. S.
    • Kremer,R. J.
    • Sudduth,K. A.
    • Kitchen,N. R.
    • Lerch,R. N.
    • Baffaut,C.
    • Stott,D. E.
    • Karlen,D. L.
    • Sadler,E. J.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 4
  • Year: 2015
  • Summary: The Conservation Effects Assessment Project (CEAP). was initiated in 2002 to quantify the potential benefits of conservation management practices throughout the nation. Within the Central Claypan Region of Missouri, the Salt River Basin was selected as a benchmark watershed for soil and water quality assessments. This study focuses on two objectives: (1) assessing soil quality for 15 different annual cropping and perennial vegetation systems typically employed in this region, and (2) evaluating relationships among multiple measured soil quality indicators (SQIs). Management practices included annual versus perennial vegetation, and varying grass species composition (cool-season versus warm-season), tillage intensity (no-till versus mulch-till), biomass removal, rotation phase, crop rotation (corn [Zea mays L.]-soybean [Glycine max L. Merr] versus corn-soybean-wheat [Triticum aestivum L.]) and incorporation of cover crops into the rotation. Soil samples were obtained in 2008 from 0 to 5 cm (0 to 2 in) and 5 to 15 cm (2 to 6 in) depth layers. Ten biological, physical, chemical, and nutrient SQIs were measured and scored using the Soil Management Assessment Framework (SMAF). Across SQIs, biological and physical indicators were the most sensitive to management effects, reflecting significant differences in organic carbon (C), mineralizable nitrogen (N), beta-glucosidase, and bulk density. In the 0 to 5 cm layer, perennial systems demonstrated the greatest SMAF scores, ranging from 93% to 97% of the soil's inherent potential. Scores for annual cropping systems ranged from 78% to 92%: diversified no-till, corn soybean wheat rotation with cover crops (92%) > no-till, corn-soybean rotation without cover crops (88%) > mulch-till corn-soybean rotation without cover crops (84%). Conversely, in the 5 to 15 cm layer, no-till cropping systems scored lower for overall soil function (58% to 61%) than mulch-till systems (65% to 66%). In the 0 to 5 cm layer, biological soil quality under the diversified no-till system with cover crops was 11% greater than under no-till without cover crops, and 20% greater than under mulch-till without cover crops. The effect of rotation phase was primarily reflected in 64% lower mineralizable N following corn relative to soybean. Additionally, soil nutrient function was significantly affected by biomass removal. The results of this study demonstrate that the benefits of conservation management practices extend beyond soil erosion reduction and improved water quality by highlighting the potential for enhanced soil quality, especially biological soil function. In particular, implementing conservation management practices on marginal and degraded soils in the claypan region can enhance long-term sustainability in annual cropping systems and working grasslands through improved soil quality.
  • Authors:
    • Wegner,B. R.
    • Kumar,S.
    • Osborne,S. L.
    • Schumacher,T. E.
    • Vahyala,I. E.
    • Eynard,A.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 4
  • Year: 2015
  • Summary: Excessive removal of crop residue has been shown to degrade soil organic carbon (SOC), and hence soil quality. Our objective was to assess the impacts of corn (Zea mays L.) residue removal and cover crops on various soil quality indicators. The experiment was conducted on a silty clay loam soil with and without a cover crop following three residue removal treatments. The low residue removal (LRR) treatment consisted of harvesting corn grain, leaving all other plant materials on the soil surface. Medium residue removal (MRR) consisted of harvesting grain, then chopping, windrowing and baling the remaining residue. The high residue removal (HRR) consisted of cutting the stalks 0.15 m from the ground and removing essentially all above-ground biomass. Crop residue removal significantly impacted measured soil properties including SOC, but cover cropping had minimal effects. The LRR treatment resulted in higher SOC concentrations and increased aggregate stability compared with other treatments. Residue removal significantly impacted the microbial activity as measured by hydrolysis of fluorescein diacetate (FDA). This study confirmed that HRR rates lead to SOC decomposition and adversely affect soil properties and soil quality. Soil conservation and emerging uses for crop residues must be balanced. Therefore, before making any decision to harvest crop residues, it is essential to have accumulated more C in the residue and supplemental cover crops than is needed to maintain equilibrium SOC levels. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All rights reserved.
  • Authors:
    • Wilson,T. M.
    • McGowen,B.
    • Mullock,J.
    • Arnall,D. B.
    • Warren,J. G.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Fertilizer-induced N 2O-N emissions (the difference between fertilized and unfertilized soils) are estimated to be 0.01 kg N 2O-N kg -1 of applied N. One approach to limiting N 2O-N production in soils is by improving nitrogen use efficiency (NUE) in dryland agricultural systems. However, baseline data on the rate of emissions is needed to determine the potential impact that these efforts might have on N 2O-N concentrations in the atmosphere. A study was established in a long-term continuous winter wheat ( Triticum aestivum L.) fertility experiment in Stillwater, OK, to determine the effects of N rate on N 2O-N emissions from a dryland winter wheat-summer fallow system in the southern Great Plains of the United States to fill this knowledge gap. Cumulative emissions of N 2O-N varied from year to year and were influenced by environment and N rate. Emissions following N fertilizer application were typically highest following N application, as well as toward the end of the summer fallow period, when summer rainfall and temperatures were conducive for N 2O-N production chambers within plots historically receiving 134 kg N ha -1 annually went unfertilized for the 2012-2013 and 2013-2014 crop years and produced N 2O-N emissions equivalent to the 45 and 90 kg N ha -1 rate treatments. Annual cumulative emissions ranged from 0.009 to 0.024 kg N 2O-N kg -1 N applied with an average of 0.015 kg N 2O-N kg -1 N applied, illustrating the variability in N 2O-N emissions.
  • Authors:
    • Woli,K. P.
    • Ruiz-Diaz,D. A.
    • Kaiser,D. E.
    • Mallarino,A. P.
    • Sawyer,J. E.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: An on-farm study was conducted in Iowa from 2004 to 2006 at 18 sites to evaluate corn ( Zea mays L.) grain yield (GY) and soil- and plant-test responses to poultry manure (PM) nutrient application at the field scale. A control and two target PM rates based on total N (PM-N) were applied in randomized field-length strips with three replications. Corn GY responded positively to PM applications. While N, P, and K plant and soil tests were related to PM nutrient rates, there was considerable variation, and relationships were probably influenced by the multiple applied nutrients. Soil-test P and soil-test K across sites increased linearly with increasing PM total P and K rates and with large increases from the high rates. This confirms high P and K crop availability. Grain yield responses to PM decreased linearly with increasing leaf chlorophyll meter (CM) and late spring soil NO 3-N test (LSNT) values but were not related to end-of-season lower corn stalk NO 3-N test values. No N test had a plateau relationship with GY, suggesting no excess N supply despite large PM-N rates. This confirms low first-year PM-N availability. The relationship between CM and LSNT indicated a critical LSNT value at 24 mg kg -1, similar to that from previous small-plot research. This field-scale study showed that PM is a valuable nutrient resource. However, due to PM multinutrient content and differences in availability, the nutrient causing GY and plant- or soil-test results often cannot be clearly identified and results need careful interpretation for reliable use.