• Authors:
    • Grosso, S. J. del
    • Blaylock, A. D.
    • Snyder, C. S.
    • Halvorson, A. D.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 2
  • Year: 2014
  • Summary: Enhanced-efficiency N fertilizers (EENFs) have potential for mitigating N 2O emissions from N-fertilized cropping systems. Stabilized EENFs contain nitrification and/or urease inhibitors. Slow-release EENFs contain N components that are slowly released with variable release rates. Controlled-release EENFs release N at more predictable rates. The effectiveness of several EENFs in reducing soil N 2O emissions from a clay loam soil under irrigated, corn ( Zea mays L.)-based production systems in Colorado (2002-2012) was investigated. A controlled-release, polymer-coated urea, ESN, reduced N 2O emissions by 42% compared with urea and 14% compared with urea-NH 4NO 3 solution (UAN) in no-till and strip-till environments, but had no effect in a conventional tillage environment. A stabilized urea source, SuperU, reduced N 2O emissions by 46% compared with urea and 21% compared with UAN. A stabilized UAN source, UAN+AgrotainPlus, reduced N 2O emissions by 61% compared with urea and 41% compared with UAN alone. A slow-release UAN source, UAN+Nfusion, reduced N 2O emissions by 57% compared with urea and 28% compared with UAN. Urea-NH 4NO 3 reduced N 2O emissions by 35% compared with urea. A linear increase in N 2O emissions with increasing N rate was observed for untreated urea and UAN. Developers of management protocols to reduce N 2O emissions from irrigated cropping systems in semiarid areas can use this information to estimate reductions in N 2O emissions when EENFs are used. Policymakers can use this information to help determine financial credits needed to encourage producers to use these technologies in their crop production systems.
  • Authors:
    • Gao, Z. Q.
    • Yang, W. S.
    • Li, P.
    • Ju, H.
    • Merchant, A.
    • Ma, Z. Y.
    • Han, X.
    • Gao, J.
    • Hao, X. Y.
    • Lin, E.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 192
  • Year: 2014
  • Summary: Investigations across the world have elucidated common chemical and physiological responses of plants to the influence of elevated atmospheric CO 2 concentration ([CO 2]). Focus is now turning to the influence of elevated [CO 2] on yield quality among a number of globally important crops including soybean ( Glycine max (L.) Merr). Soybean cv. Zhonghuang 35 was grown in a free-air CO 2 enrichment (FACE) field experiment at Changping-Beijing (China) under ambient (41516 mol mol -1) and elevated (55019 mol mol -1) CO 2 concentrations. Results showed that elevated [CO 2] increased the yields of soybean seeds (g m -2) by 26% and 31% respectively, in 2009 and 2011. Total protein concentration in seeds was significantly reduced by 3.3% under CO 2 enrichment, but oil concentration increased by 2.8%. Accordingly, most proteinogenic amino acid concentrations were significantly reduced under elevated [CO 2], whilst two fatty acids (linoleic acid and palmitic acid) increased in concentration. The protein and oil yield per unit ground area increased by 24.5% and 32.0%, respectively. Results indicate that whilst future elevated atmospheric [CO 2] may improve the oil quantity of soybean, corresponding reductions in the nutritive value are likely to occur.
  • Authors:
    • Asseng, S.
    • Zhu, Y.
    • Cao, W. X.
    • Tian, L. Y.
    • Liu, L. L.
    • Liu, B.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 2
  • Year: 2014
  • Summary: Wheat is sensitive to high temperatures, but the spatial and temporal variability of high temperature and its impact on yield are often not known. An analysis of historical climate and yield data was undertaken to characterize the spatial and temporal variability of heat stress between heading and maturity and its impact on wheat grain yield in China. Several heat stress indices were developed to quantify heat intensity, frequency, and duration between heading and maturity based on measured maximum temperature records of the last 50 years from 166 stations in the main wheat-growing region of China. Surprisingly, heat stress between heading and maturity was more severe in the generally cooler northern wheat-growing regions than the generally warmer southern regions of China, because of the delayed time of heading with low temperatures during the earlier growing season and the exposure of the post-heading phase into the warmer part of the year. Heat stress between heading and maturity has increased in the last decades in most of the main winter wheat production areas of China, but the rate was higher in the south than in the north. The correlation between measured grain yields and post-heading heat stress and average temperature were statistically significant in the entire wheat-producing region, and explained about 29% of the observed spatial and temporal yield variability. A heat stress index considering the duration and intensity of heat between heading and maturity was required to describe the correlation of heat stress and yield variability. Because heat stress is a major cause of yield loss and the number of heat events is projected to increase in the future, quantifying the future impact of heat stress on wheat production and developing appropriate adaptation and mitigation strategies are critical for developing food security policies in China and elsewhere.
  • Authors:
    • Hatfield, J. L.
    • Parkin, T. B.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 2
  • Year: 2014
  • Summary: Fertilizer application in crop production agriculture is a major factor influencing soil emissions of the greenhouse gas N 2O. Enhanced efficiency fertilizers (EEFs) have the potential to decrease N 2O emissions by improving the synchrony between soil N supply and crop N demand. This study was conducted to compare the effects of N 2O emissions from soil cropped to corn ( Zea mays L.) and EEFs and conventional fertilizers. During a 3-yr period, growing-season N 2O emissions were quantified in unfertilized check plots and plots fertilized with urea-NH 4NO 3 (UAN), UAN containing the urease and nitrification stabilizer AgrotainPlus (UAN+Ag), a stabilized urea containing urease and nitrification inhibitors (SuperU), and a controlled-release polymer-coated urea (ESN). In the third year of the study, conventional urea and an additional fertilizer formulation, Nutrisphere, were evaluated. We observed no reductions in cumulative seasonal N 2O emissions from treatments fertilized with the EEFs in any of the study years. Generally, N 2O emissions were significantly higher than emissions from the check (no fertilizer) treatment. There were no differences among fertilizer types except in 2009 when the ESN treatment had significantly higher emissions than the check, UAN, and UAN+Ag treatments. Our results indicate that, due to the episodic nature of N 2O emissions induced by rainfall events, reduction of N 2O emissions through the use of EEFs may be limited in rainfed regions.
  • Authors:
    • Nalley, L. L.
    • Barkley, A.
    • Tack, J.
  • Source: Climatic Change
  • Volume: 125
  • Issue: 3-4
  • Year: 2014
  • Authors:
    • Zhang, Y. M.
    • Dong, W. X.
    • Schaefer, D. A.
    • Oenema, O.
    • Ming, H.
    • Hu, C. S.
    • Wang, Y. Y.
    • Li, X. X.
  • Source: PLOS ONE
  • Volume: 9
  • Issue: 6
  • Year: 2014
  • Summary: The production and consumption of the greenhouse gases (GHGs) methane (CH 4), carbon dioxide (CO 2) and nitrous oxide (N 2O) in soil profile are poorly understood. This work sought to quantify the GHG production and consumption at seven depths (0-30, 30-60, 60-90, 90-150, 150-200, 200-250 and 250-300 cm) in a long-term field experiment with a winter wheat-summer maize rotation system, and four N application rates (0; 200; 400 and 600 kg N ha -1 year -1) in the North China Plain. The gas samples were taken twice a week and analyzed by gas chromatography. GHG production and consumption in soil layers were inferred using Fick's law. Results showed nitrogen application significantly increased N 2O fluxes in soil down to 90 cm but did not affect CH 4 and CO 2 fluxes. Soil moisture played an important role in soil profile GHG fluxes; both CH 4 consumption and CO 2 fluxes in and from soil tended to decrease with increasing soil water filled pore space (WFPS). The top 0-60 cm of soil was a sink of atmospheric CH 4, and a source of both CO 2 and N 2O, more than 90% of the annual cumulative GHG fluxes originated at depths shallower than 90 cm; the subsoil (>90 cm) was not a major source or sink of GHG, rather it acted as a 'reservoir'. This study provides quantitative evidence for the production and consumption of CH 4, CO 2 and N 2O in the soil profile.
  • Authors:
    • Mengel, D. B.
    • Hettiarachchi, G. M.
    • Khatiwada, R.
    • Fei, M.
  • Source: Journal
  • Volume: 179
  • Issue: 3
  • Year: 2014
  • Summary: Crop yields are limited primarily by unavailability of nutrients in agricultural soil. Adoption of reduced-tillage and no-tillage systems leads to stratification of nutrients in surface soil, so management of phosphorus (P) in these systems is a major issue. The objective of this research was to understand the influence of placement (broadcast vs. deep-placed P) and fertilizer source (granular vs. liquid P) on the reaction products of P under greenhouse conditions using soil columns. Phosphorus was added at a rate of 75 kg/ha to two soils: an acid soil from Manhattan, KS, and a slightly acid to neutral soil from Ottawa, KS. At 5 weeks after P application, soil pH, resin-extractable P, and speciation of P in soils were determined at different distances from the point of fertilizer application. Scanning electron microscope with energy-dispersive X-ray analysis and synchrotron-based X-ray absorption near-edge structure spectroscopy were used to understand P speciation. Results for P fertilizer sources and placement with respect to resin-extractable P showed no clear differences between the treatments except for granular broadcast and granular deep-placed treatments in the Ottawa soil. Reaction products formed after application of P in two soils showed some clear differences. The X-ray absorption near-edge structure speciation revealed that Fe-P-like forms dominated in the acidic soil, whereas adsorbed and Fe and Ca-P-like forms dominated in the neutral to slightly acid soil. No clear trends in reaction products were detected with respect to P source or the P placement method. Furthermore, scanning electron microscope with energy-dispersive X-ray analysis of incubated fertilizer granules extracted from soils at 5 weeks showed enrichment of Al, Fe, and Ca in the zones of remaining P in incubated granules, indirectly indicating that these cations enter and or remaining in the granules and begin to react with P before the granules dissolve completely.
  • Authors:
    • Fisher,S.
    • Karunanithi,A.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector
  • Year: 2014
  • Summary: Local policy makers typically do not have useful, quantitative metrics to compare environmental costs and benefits of urban vegetable production versus the large-scale commercial production in the typical grocery store supply chain. While urban agriculture has been championed as a way to address social issues such as food access and nutrition, we know relatively little about net environmental benefits, if any. The study combines a comparative life cycle assessment of vegetables with effects of direct and indirect land use change resulting from the urban vegetable production. This paper presents a methodology and selected results of scenarios of land use change due to urban vegetable production address resource use, greenhouse gas emissions, employment, and soil organic carbon. Surprisingly, urban vegetable production is not categorically favorable for each metric; several key parameters can shift the balance in favor or out of favor for either growing format, and these parameters are distinctly bottom-up.
  • Authors:
    • Torres,C. M.
    • Anton,A.
    • Castells,F.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector (LCA Food 2014)
  • Year: 2014
  • Summary: Certain complexities in the agricultural production differentiate this sector from the conventional industrial processes. The main feature to take into account is that the resources consumption and production is subjected to high variability in soil, rainfall and latitude. We show here an environmental tool developed in close cooperation with farmers in order to achieve applicability and comprehensibility. The procedure relies on the data retrieved from parcel management monitoring of different crops, mostly allocated in Catalonia and Ebro river watershed region (NE Spain). A set of comprehensive but also simple reports are provided, including material and energy balances, agronomic efficiencies and water and carbon footprints. The calculations also cover impacts due to infrastructure, including the estimation of materials in the use of greenhouses. Besides, a simple algorithm for reporting uncertainty using an approximation method of error propagation was added using the input uncertainties as defined by their data pedigree.
  • Authors:
    • Bathke, D. J
    • Oglesby, R. J.
    • Rowe, C. M.
    • Wilhite, D. A.
  • Year: 2014
  • Summary: The goal of this report is to inform policy makers, natural resource managers, and the public about the state of the science on climate change, current projections for ongoing changes over the twenty-first century, current and potential future impacts, and the management and policy implications of these changes. Hopefully, this report will lead to a higher degree of awareness and the initiation of timely and appropriate strategic actions that will enable Nebraskans to prepare for and adapt to future changes to our climate.