• Authors:
    • Naab,J. B.
    • Mahama,G. Y.
    • Koo,J.
    • Jones,J. W.
    • Boote,K. J.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 1
  • Year: 2015
  • Summary: Sustainable management practices are needed to enhance soil organic carbon (SOC) in degraded soils in semi-arid West Africa. We studied the effects of three amounts of nitrogen (N) (0, 60 and 120 kg N ha(-1)) and three amounts of phosphorus (P) fertilizer (0, 26 and 39 kg P ha(-1)) application over four seasons on maize residue production, residue C, N, and P concentrations, and their impacts on SOC, total soil nitrogen (TSN), and total soil phosphorus (TSP) in the 0-20 cm soil layer. Combined application of N and P fertilizers substantially increased maize grain yield on average by 294 % and biomass produced and returned to the soil by about 60-70 % compared with no fertilization. Annual C, N, and P inputs from crop residue were significantly higher with combined application of N and P fertilizer. The increased amount of crop residue and consequent increased residue C, N and P returned to the soil significantly increased SOC, TSN and TSP in the 0-20 cm soil layer after four seasons. There was a significant correlation between the amount of crop residues returned to the soil over four seasons and SOC (r = 0.82; P = 0.007), TSN (r = 0.75; P = 0.020) and TSP (r = 0.69; P = 0.039). We concluded from these experiments that returning crop residues, application of inorganic fertilizer improves SOC, TSN and TSP concentrations and enhances crop productivity. The farmers who traditionally remove crop residues for fodder and fuel will require demonstration of the relative benefits of residues return to soil for sustainable crop productivity.
  • Authors:
    • Zuber,S. M.
    • Behnke,G. D.
    • Nafziger,E. D.
    • Villamil,M. B.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: Recent increases in corn ( Zea mays L.) production in the U.S. Corn Belt have necessitated the conversion of rotations to continuous corn, and an increase in the frequency of tillage. The objective of this study was to assess the effect of rotation and tillage on soil physical and chemical properties in soils typical of Illinois. Sequences of continuous corn (CCC), 2-yr corn-soybean [ Glycine max (L.) Merr.] (CS) rotation, 3-yr corn-soybean-wheat ( Triticum aestivum L.) (CSW) rotation, and continuous soybean (SSS) were split into conventional tillage (CT) and no-till (NT) subplots at two Illinois sites. After 15 yr, bulk density (BD) under NT was 2.4% greater than under CT. Water aggregate stability (WAS) was 0.84 kg kg -1 under NT compared to 0.81 kg kg -1 under CT. Similarly, soil organic carbon (SOC) and total nitrogen (TN) were greater under NT than under CT with SOC values for 0 to 60 cm of 96.0 and 91.0 Mg ha -1 and TN values of 8.87 and 8.40 Mg ha -1 for NT and CT, respectively. Rotations affected WAS, TN, and K levels with WAS being greatest for the CSW rotation at 0.87 kg kg -1, decreasing with more soybean years (CS, 0.82 kg kg -1 and SSS, 0.79 kg kg -1). A similar pattern was detected for TN and exchangeable K. Results indicated that while the use of NT improved soil quality, long-term implementation of continuous corn had similar soil quality parameters to those found under a corn-soybean rotation.
  • Authors:
    • Cuello,J. P.
    • Hwang HyunYoung
    • Gutierrez,J.
    • Kim SangYoon
    • Kim PilJoo
  • Source: Applied Soil Ecology
  • Volume: 91
  • Issue: 1
  • Year: 2015
  • Summary: Plastic film mulching (PFM) is an agricultural management practice that is commonly used to suppress weed growth. However, its effect on greenhouse gas (GHG) emissions has not been well evaluated. To investigate the effect of PFM on GHG emissions and crop productivities, black PFM and no-mulching plots were installed as the main treatment, and three sub-treatments, chemical fertilizer (NPK) and two green manures, were arranged within each main treatment. Two cover crops (hairy vetch and barley) with different carbon/nitrogen (C/N) ratios were cultivated in the two green manure treatments during the fallow season. The aboveground biomasses of vetch (23-25 Mg fresh weight ha -1) and barley (10-11 Mg ha -1) were incorporated before maize seedling transplanting. Maize was cultivated without chemical fertilization in the two green manure treatments, whereas the recommended chemical fertilizers were applied in the NPK treatment. During two annual cropping seasons, the emission rates of methane (CH 4) and nitrous oxide (N 2O) gases were simultaneously monitored once a week using the closed-chamber method. Total global warming potential (GWP) was calculated as CO 2 equivalents by multiplying the seasonal CH 4 and N 2O fluxes by 25 and 298, respectively. Irrespective of soil amendments, PFM significantly increased soil temperature and moisture content by a mean of 2°C and 0.04 m 3 m -3 over no-mulching, respectively. Plastic film mulching increased grain productivity by 8-33% over no-mulching. However, PFM significantly decreased soil organic matter content and largely increased the two major GHG emissions. As a result, PFM increased the total GWP by 12-82% over no-mulching, irrespective of the soil amendments. In conclusion, more sustainable mulching systems should be developed that can sustain soil quality and minimize environmental impacts, including GHG emissions.
  • Authors:
    • Deng,Q.
    • Hui,D. F.
    • Wang,J. M.
    • Iwuozo,S.
    • Yu,C. L.
    • Jima,T.
    • Smart,D.
    • Reddy,C.
    • Dennis,S.
  • Source: Web Of Knowledge
  • Volume: 10
  • Issue: 4
  • Year: 2015
  • Summary: Background: A three-year field experiment was conducted to examine the responses of corn yield and soil nitrous oxide (N 2O) emission to various management practices in middle Tennessee. Methodology/Principal Findings: The management practices include no-tillage + regular applications of urea ammonium nitrate (NT-URAN); no-tillage + regular applications of URAN + denitrification inhibitor (NT-inhibitor); no-tillage + regular applications of URAN + biochar (NT-biochar); no-tillage + 20% applications of URAN + chicken litter (NT-litter), no-tillage + split applications of URAN (NT-split); and conventional tillage + regular applications of URAN as a control (CT-URAN). Fertilizer equivalent to 217 kg N ha -1 was applied to each of the experimental plots. Results showed that no-tillage (NT-URAN) significantly increased corn yield by 28% over the conventional tillage (CT-URAN) due to soil water conservation. The management practices significantly altered soil N 2O emission, with the highest in the CT-URAN (0.48 mg N 2O m -2 h -1) and the lowest in the NT-inhibitor (0.20 mg N 2O m -2 h -1) and NT-biochar (0.16 mg N 2O m -2 h -1) treatments. Significant exponential relationships between soil N 2O emission and water filled pore space were revealed in all treatments. However, variations in soil N 2O emission among the treatments were positively correlated with the moisture sensitivity of soil N 2O emission that likely reflects an interactive effect between soil properties and WFPS. Conclusion/Significance: Our results indicated that improved fertilizer and soil management have the potential to maintain highly productive corn yield while reducing greenhouse gas emissions.
  • Authors:
    • Elshout,P. M. F.
    • van Zelm,R.
    • Balkovic,J.
    • Obersteiner,M.
    • Schmid,E.
    • Skalsky,R.
    • van der Velde,M.
    • Huijbregts,M. A. J.
  • Source: Nature Climate Change
  • Volume: 5
  • Issue: 6
  • Year: 2015
  • Summary: A global increase in the demand for crop-based biofuels may be met by cropland expansion, and could require the sacrifice of natural vegetation. Such land transformation alters the carbon and nitrogen cycles of the original system, and causes significant greenhouse-gas emissions, which should be considered when assessing the global warming performance of crop-based biofuels. As an indicator of this performance we propose the use of greenhouse-gas payback time (GPBT), that is, the number of years it takes before the greenhouse-gas savings due to displacing fossil fuels with biofuels equal the initial losses of carbon and nitrogen stocks from the original ecosystem. Spatially explicit global GPBTs were derived for biofuel production systems using five different feedstocks (corn, rapeseed, soybean, sugarcane and winter wheat), cultivated under no-input and high-input farm management. Overall, GPBTs were found to range between 1 and 162 years (95% range, median: 19 years) with the longest GPBTs occurring in the tropics. Replacing no-input with high-input farming typically shortened the GPBTs by 45 to 79%. Location of crop cultivation was identified as the primary factor driving variation in GPBTs. This study underscores the importance of using spatially explicit impact assessments to guide biofuel policy.
  • Authors:
    • Emery,I.
    • Mosier,N.
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 4
  • Year: 2015
  • Summary: Little is known about the contributions of biomass feedstock storage to the net greenhouse gas emissions from cellulosic biofuels. Direct emissions of methane and nitrous oxide during decomposition in storage may contribute substantially to the global warming potential of biofuels. In this study, laboratory-scale bales of switchgrass and corn stover were stored under a range of moisture (13.0-32.9%) and temperature (5-35°C) conditions and monitored for O 2 consumption and CO 2, CH 4, and N 2O production over 8 weeks. Gas concentrations and emissions rates were highly variable within and between experimental groups. Stover bales produced higher CO 2 concentrations ( P=0.0002) and lower O 2 ( P<0.0001) during storage than switchgrass bales. Methane concentrations (1.8-2100 ppm) were inversely correlated with bale moisture ( P<0.05), with emissions rates ranging from 4.4-914.9 g kg -1 DM day -1. Nitrous oxide concentrations ranged from 0 to 31 ppm, and emissions from switchgrass bales inversely correlated with temperature and moisture ( P<0.0001). Net global warming potential from each treatment (0-2.4 gCO 2e kg -1 DM) suggests that direct emission of methane and nitrous oxide from aerobically stored feedstocks have a small effect on net global warming potential of cellulosic biofuels.
  • Authors:
    • Kibue,Grace Wanjiru
    • Pan,Genxing
    • Zheng,Jufeng
    • Li Zhengdong
    • Mao,Li
  • Source: Environment, Development and Sustainability
  • Volume: 17
  • Issue: 3
  • Year: 2015
  • Summary: Agricultural production is a complex interaction between human and natural environment, making agriculture both significantly responsible and vulnerable to climate change. China, whose socioeconomy is fundamentally dependent on agriculture, is already experiencing climate-change-related issues that threaten food security and sustainable development. Climate change mitigation and adaptation are of great concern to ensure food security for the growing population and improve the livelihoods of poor smallholder producers. A questionnaire survey was conducted in Henan Province, China to assess agronomic practices of smallholder farmers, adaptation strategies and how climate change awareness and perceptions influence the farmers' choice of agronomic practices. The results showed that the vast majority of farmers owned < 10 Chinese Mu (0.7 ha) and nearly all farmers' relied on intensive use of chemical fertilizers and pesticides to increase yield at the detriment of environment. However, farmers who were aware of climate change had adopted agronomic practices that reduce impacts of climate change. Information about climate change, lack of incentives, lack of credit facilities and small farm sizes were major hindrance to adaptation and adoption of farming practices that can reduce impacts of climate change. This study recommends that research findings should be disseminated to farmers in timely and appropriate ways. The central government should formulate policies to include subsidies and incentives for farmers to motivate adoption of eco-friendly agronomic practices.
  • Authors:
    • Pohl,M.
    • Hoffmann,M.
    • Hagemann,U.
    • Giebels,M.
    • Borraz,E. Albiac
    • Sommer,M.
    • Augustin,J.
  • Source: Biogeosciences
  • Volume: 12
  • Issue: 9
  • Year: 2015
  • Summary: The drainage and cultivation of fen peatlands create complex small-scale mosaics of soils with extremely variable soil organic carbon (SOC) stocks and groundwater levels (GWLs). To date, the significance of such sites as sources or sinks for greenhouse gases such as CO2 and CH4 is still unclear, especially if the sites are used for cropland. As individual control factors such as GWL fail to account for this complexity, holistic approaches combining gas fluxes with the underlying processes are required to understand the carbon (C) gas exchange of drained fens. It can be assumed that the stocks of SOC and N located above the variable GWL - defined as dynamic C and N stocks - play a key role in the regulation of the plant- and microbially mediated CO2 fluxes in these soils and, inversely, for CH4. To test this assumption, the present study analysed the C gas exchange (gross primary production - GPP; ecosystem respiration - R-eco; net ecosystem exchange - NEE; CH4) of maize using manual chambers for 4 years. The study sites were located near Paulinenaue, Germany, where we selected three soil types representing the full gradient of GWL and SOC stocks (0-1 m) of the landscape: (a) Haplic Arenosol (AR; 8 kg C m(-2)); (b) Mollic Gleysol (GL; 38 kg C m(-2)); and (c) Hemic Histosol (HS; 87 kg C m(-2)). Daily GWL data were used to calculate dynamic SOC (SOCdyn) and N (N-dyn) stocks. Average annual NEE differed considerably among sites, ranging from 47 +/- 30 g C m(-2) yr(-1) in AR to -305 +/- 123 g C m(-2) yr(-1) in GL and -127 +/- 212 g C m(-2) yr(-1) in HS. While static SOC and N stocks showed no significant effect on C fluxes, SOCdyn and N-dyn and their interaction with GWL strongly influenced the C gas exchange, particularly NEE and the GPP : R-eco ratio. Moreover, based on nonlinear regression analysis, 86% of NEE variability was explained by GWL and SOCdyn. The observed high relevance of dynamic SOC and N stocks in the aerobic zone for plant and soil gas exchange likely originates from the effects of GWL-dependent N availability on C formation and transformation processes in the plant-soil system, which promote CO2 input via GPP more than CO2 emission via R-eco. The process-oriented approach of dynamic C and N stocks is a promising, potentially generalisable method for system-oriented investigations of the C gas exchange of groundwater-influenced soils and could be expanded to other nutrients and soil characteristics. However, in order to assess the climate impact of arable sites on drained peatlands, it is always necessary to consider the entire range of groundwater-influenced mineral and organic soils and their respective areal extent within the soil landscape.
  • Authors:
    • Torres,C. M. M. E.
    • Kohmann,M. M.
    • Fraisse,C. W.
  • Source: Agricultural Systems
  • Volume: 137
  • Year: 2015
  • Summary: Agriculture is an important source of greenhouse gases (GHG), especially from crop production practices and enteric fermentation by ruminant livestock. Improved production practices in agriculture and increase in terrestrial carbon sinks are alternatives for mitigating GHG emissions in agriculture. The objective of this study was to estimate GHG emissions from hypothetical farm enterprise combinations in the southeastern United States with a mix of cropland and livestock production and estimate the area of forest plantation necessary to offset these emissions. Four different farm enterprise combinations (Cotton; Maize; Peanut; Wheat+Livestock+Forest) with different production practices were considered in the study resulting in different emission scenarios. We assumed typical production practices of farm operations in the region with 100 ha of cropland area and a herd of 50 cows. GHG emissions were calculated regarding production, storage and transportation of agrochemicals (pre-farm) and farm activities such as fertilization, machinery operation and irrigation (on-farm). Simulated total farm GHG emissions for the different farm enterprise combinations and production practices ranged from 348.8 t CO 2e year -1 to 765.6 t CO 2e year -1. The estimated forest area required to neutralize these emissions ranged from 19 ha to 40 ha. In general, enterprise combinations with more intense production practices that include the use of irrigation resulted in higher total emissions but lower emissions per unit of commodity produced.
  • Authors:
    • Bagley,Justin E.
    • Miller,Jesse
    • Bernacchi,Carl J.
  • Source: Plant Cell Environment
  • Volume: 38
  • Issue: 9
  • Year: 2015
  • Summary: The potential impacts of climate change in the Midwest United States present unprecedented challenges to regional agriculture. In response to these challenges, a variety of climate-smart agricultural methodologies have been proposed to retain or improve crop yields, reduce agricultural greenhouse gas emissions, retain soil quality and increase climate resilience of agricultural systems. One component that is commonly neglected when assessing the environmental impacts of climate-smart agriculture is the biophysical impacts, where changes in ecosystem fluxes and storage of moisture and energy lead to perturbations in local climate and water availability. Using a combination of observational data and an agroecosystem model, a series of climate-smart agricultural scenarios were assessed to determine the biophysical impacts these techniques have in the Midwest United States. The first scenario extended the growing season for existing crops using future temperature and CO2 concentrations. The second scenario examined the biophysical impacts of no-till agriculture and the impacts of annually retaining crop debris. Finally, the third scenario evaluated the potential impacts that the adoption of perennial cultivars had on biophysical quantities. Each of these scenarios was found to have significant biophysical impacts. However, the timing and magnitude of the biophysical impacts differed between scenarios. This study assessed the biophysical impacts of several climate-smart agricultural practices in the Midwest United States. Specifically we investigated the biophysical impacts of adapting crops to extended growing season length, expanding no-till agriculture, and the adoption of perennial cultivars. We found that each of these practices had significant biophysical impacts, but the seasonality and extent of the impacts differed between scenarios.