19602015
  • Authors:
    • Uzoma,K. C.
    • Smith,W.
    • Grant,B.
    • Desjardins,R. L.
    • Gao XiaoPeng
    • Hanis,K.
    • Tenuta,M.
    • Goglio,P.
    • Li,C. S.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 206
  • Year: 2015
  • Summary: Biogeochemical models are useful tools for integrating the effects of agricultural management on GHG emissions; however, their development is often hampered by the incomplete temporal and spatial representation of measurements. Adding to the problem is that a full complement of ancillary measurements necessary to understand and validate the soil processes responsible for GHG emissions is often not available. This study presents a rare case where continuous N 2O emissions, measured over seven years using a flux gradient technique, along with a robust set of ancillary measurements were used to assess the ability of the DNDC model for estimating N 2O emissions under varying crop-management regimes. The analysis revealed that the model estimated soil water content more precisely in the normal and wet years (ARE 3.4%) than during the dry years (ARE 11.5%). This was attributed to the model's inability to characterize episodic preferential flow through clay cracks. Soil mineral N across differing management regimes (ARE 2%) proved to be well estimated by DNDC. The model captured the relative differences in N 2O emissions between the annual (measured: 35.5 kg N 2O-N ha -1, modeled: 30.1 kg N 2O-N ha -1) and annual-perennial (measured: 26.6 kg N 2O-N ha -1, modeled: 21.2 kg N 2O-N ha -1) cropping systems over the 7 year period but overestimated emissions from alfalfa production and underestimated emissions after spring applied anhydrous ammonia. Model predictions compared well with the measured total N 2O emissions (ARE -11%) while Tier II comparison to measurements (ARE -75%) helped to illustrate the strengths of a mechanistic approach in characterizing the site specific drivers responsible for N 2O emissions. Overall this study demonstrated the benefits of having near continuous GHG flux measurements coupled with detailed ancillary measurements towards identifying soil process interactions responsible for regulating GHG emissions.
  • Authors:
    • Wang,Jinzhou
    • Wang,Xiujun
    • Xu,Minggang
    • Feng,Gu
    • Zhang,Wenju
    • Lu,Chang'ai
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: Straw has been commonly incorporated to maintain soil fertility and crop productivity in China, but effects of long-term straw incorporation on crop yield, soil organic carbon (SOC) and total nitrogen (TN) have not been thoroughly evaluated. Thus, this study analyzed data collected in long-term (> 10-year) trials across the major agricultural zones of China. Across the trials, relative to straw removal, straw return significantly increased crop yield, SOC and TN (by 7.0, 10.1 and 11.0 %, respectively). In some trials with winter wheat in northern China, straw return reduced yield by 0.6-7.1 %. The effects of straw return on SOC and TN were not significantly affected by experimental duration, land use type and cropping system, but positively and linearly related to the inputs of straw-C and -N, respectively. Interestingly, SOC and TN responses to straw return were decoupled in upland and upland-paddy soils in China, but not in paddy soils. Mean values of straw-C sequestration efficiency (7.7, 10.3 and 9.4 %, under corn, wheat and rice, respectively) indicate that 100 % straw return could increase SOC by 281.7 Tg C in 18 years (the mean experimental period of the considered studies) in China. Our analyses demonstrate that straw return is an effective practice for sustaining crop productivity and soil fertility in large parts of China, but site-specific factors should be considered.
  • 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:
    • Abdullah,A. S.
    • Aziz,M. M.
    • Siddique,K. H. M.
    • Flower,K. C.
  • Source: Agricultural Water Management
  • Volume: 159
  • Year: 2015
  • Summary: We investigated the use of film-forming antitranspirants (AT) to reduce transpiration and alleviate the adverse effects of late-season drought on wheat ( Triticum aestivum L.) growth and yield. Two experiments were conducted in a controlled-temperature glasshouse from April to November 2014, to compare two watering regimes (well watered and water deficit) and three AT treatments (unsprayed control, sprayed before boot swollen and sprayed before anthesis complete). We measured plant water use, transpiration rate, stomatal conductance and photosynthesis. Relative leaf turgor was measured in real time using a non-destructive method of leaf patch clamp pressure. Drought stress reduced daily water use, transpiration rate, stomatal conductance and leaf turgor in wheat plants after about four days. In contrast, these measurements rapidly declined soon after AT application in both well-watered and water-deficit plants. Nevertheless, once soil moisture deficit increased markedly, AT-treated water-deficit plants maintained significantly higher levels of photosynthesis than untreated plants. Drought stress reduced grain yield in unsprayed control plants by more than 40%, compared to well-watered control plants, mainly due to fewer grains per spike. In contrast, drought stress with AT application prior to the most drought-sensitive boot stage reduced yield by only 14%. These results suggest that AT has the potential to improve wheat yields with late-season drought, as is common in semiarid regions; although, more research is required to test the wider applicability of these results in field conditions.
  • Authors:
    • Mereu,Valentina
    • Carboni,Gianluca
    • Gallo,Andrea
    • Cervigni,Raffaello
    • Spano,Donatella
  • Source: Climatic Change
  • Volume: 132
  • Issue: 2
  • Year: 2015
  • Summary: Climate change impact on the agricultural sector is expected to be significant and extensive in Sub-Saharan Africa, where projected increase in temperature and changes in precipitation patterns could determine sensible reductions in crop yields and concerns for food security achievement. This study presents a multi-model approach to analysing climate change impacts and associated risks for staple food crops in Nigeria. Previous attempts to evaluate climate change impacts in Nigeria had mainly focused on a reduced number of crops, with analysis limited to single experimental fields or specific areas, and in many cases considering only a limited number of climate models. In this work, crop simulation models implemented in the DSSAT-CSM software were used to evaluate climate change impacts on crop production in different Agro-Ecological Zones, considering multiple combinations of soils and climate conditions, varieties and crop management. The climate impact assessment was made using an ensemble of future climate projections, to include uncertainty related to climate projections. Even if precipitations could increase in most parts of Nigeria, this is not likely to offset the crop yield reduction due to the increase in temperatures, particularly over the medium-term period (2050), with yield decreases projected especially for cereals. The short-term effects are more uncertain and yields for cassava and millet might actually increase by 2020. Moreover, yield reductions are only partially mitigated by the direct effect of increased CO2 atmospheric concentration enhancing crop yield. In both periods and for all crops, there is a higher risk that crop yields may fall below the actual risk threshold.
  • Authors:
    • Plaza,E. H.
    • Navarrete,L.
    • Gonzalez-Andujar,J. L.
  • Source: Agriculture, Systems and Environment
  • Volume: 207
  • Year: 2015
  • Summary: Disturbances have a prominent role in structuring plant communities. However, in agroecosystems, the long-term effect of disturbances on determining trait distributions within weed communities remains little studied. We analyzed the effect of three tillage treatments, which differ in the intensity of soil disturbance, on the mean, the range and the distribution of four response traits within weed communities. We aim to test whether tillage acts as a filter restricting the range and the distribution of response traits within weed communities and leads to reduced response trait diversity or whether tilling may have a diversifying effect, creating opportunities for more phenotypes to coexist and increasing response trait diversity. To test this idea, we used data on weed abundance recorded over 24 years from an experiment in which conventional tillage (CT), minimum tillage (MT) and no-tillage (NT) systems were compared. We selected four response traits, maximum height, specific leaf area (SLA), seed weight and seed output, and computed the community weighted mean (CWM) of each trait, as well as four multi-trait metrics related to a different aspect of functional diversity. We found that soil disturbance increases available niche opportunities for weeds especially in terms of regenerative traits. CT, the greater soil disturbance, leads to a greater range and even distribution of the studied traits and that abundant weed species from CT plots hold more divergent trait values than those from MT and NT plots. Our results may be explained by the idiosyncrasy of our disturbance treatments that affect weed seed placement in the soil layers as well as the stratification and availability of soil nutrients. We also found that NT system selected for lower CWM of seed weight (and higher seed output) than MT and CT systems. NT places weed seeds mostly on the soil surface, where having a large seed output may be necessary to avoid the risk of decay or depredation. Conversely, MT and CT systems offer some advantage to other strategies such as larger seed sizes useful to germinate from depth. CWM of SLA was higher in NT and MT than in CT plots and this could be related to greater soil nutrient content in NT systems. In addition our results showed a general trend over experimental time for weed communities to increase in height (and slightly in SLA and seed production) while reducing in seed size. These features are generally associated with intensive farming systems.
  • Authors:
    • Sapkota,T. B.
    • Kaushik Majumdar
    • Jat,M. L.
  • Source: Better Crops with Plant Food
  • Volume: 99
  • Issue: 3
  • Year: 2015
  • Summary: In a collaborative effort between the International Maize and Wheat Improvement Centre and the International Plant Nutrition Institute to test, pilot and upscale Nutrient Expert (NE; a decision support system)-based fertilizer management, on-farm participatory research was conducted in 7 districts (Karnal, Kurukshetra, Kaithal, Ambala, Sonepat, Panipat, and Yamunanager) of Haryana (India) to evaluate and compare the NE-based strategies in conventional and no-till wheat production systems. For this, 15 on-farm experiments were established in 2010-11 and 2011-12. The four nutrient management treatments included: (1) NE-based recommendation; (2) NE+GreenSeeker (GS; handheld sensors): NE recommendation supplemented with GS-guided application of N; (3) SR: state fertilizer recommendation; and (4) FFP or the farmers fertilizer application practice. These treatments were compared for agronomic productivity, economic profitability and total greenhouse gas emissions. Total greenhouse gas emissions from wheat production were estimated using the Cool Farm Tool. The results showed that both grain yield and net return were higher with NE-based strategies compared to FFP and SR. The estimated total carbon footprint (i.e. GWP per tonne of wheat grain production and per US$ of net return) was also lower for NE-based strategies than other nutrient management strategies. Thus, the use of precision nutrient management tools such as NE and GS are important for increasing wheat yields and farmer profits yet minimizing the environmental footprint of wheat production.
  • Authors:
    • Sastre,C. M.
    • Gonzalez-Arechavala,Y.
    • Santos,A. M.
  • Source: Applied Energy
  • Volume: 154
  • Year: 2015
  • Summary: This paper aims to provide more accurate results in the life cycle assessment (LCA) of electricity generation from wheat straw grown in Spain through the inclusion of parameter uncertainty and variability in the inventories. We fitted statistical distributions for the all the parameter that were relevant for the assessment to take into account their inherent uncertainty and variability. When we found enough data, goodness of fit tests were performed to choose the best distribution for each parameter and, when this was not possible, we adjusted triangular or uniform distributions according to data available and expert judge. To obtain a more complete and realistic LCA, we considered the consequences of straw exportation for the agricultural system, specially the loss of soil organic carbon and the decrease of future fertility. We also took into account all the inputs, transformations and transports needed to generate electricity in a 25 MWe power plant by straw burning. The inventory data for the agricultural, the transport and the transformation phases were collected considering their most common values and ranges of variability for the Spanish case. We used Monte Carlo simulation and sensitivity analysis to obtain global warming potential (GWP) and fossil energy (FOSE) consumption of the system. These results were compared with those of the electricity generated from natural gas in Spanish power plants, as fossil reference energy system. Our results showed that for the majority of the simulations electricity from wheat straw biomass combustion produced less greenhouse gases (GHG) emissions and consumed less fossil energy than electricity from natural gas. However, only 58% of the simulations achieved the sustainability threshold of 60% GHG savings proposed by the European Union (EU). Our analysis showed that agricultural field works and the loss of soil organic carbon due to straw exportation were the most important phases for FOSE consumption and GWP respectively. According to parameters sensitivity analysis, the loss of soil organic carbon was completely dependent on the isohumic coefficient and the soil carbon content factor values. Due to this fact, local and specific estimates of these parameters are relevant tasks to be performed in order to reduce uncertainties and provide a definitive answer to the compliance of the EU sustainability criteria. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Winchester,N.
    • Reilly,J. M.
  • Source: Energy Economics
  • Volume: 51
  • Year: 2015
  • Summary: What are the feasibility, costs, and environmental implications of large-scale bioenegry? We investigate this question by developing a detailed representation of bioenergy in a global economy-wide model. We develop a scenario with a global carbon dioxide price, applied to all anthropogenic emissions except those from land use change, that rises from $25 per metric ton in 2015 to $99 in 2050. This creates market conditions favorable to biomass energy, resulting in global non-traditional bioenergy production of ~. 150 exajoules (EJ) in 2050. By comparison, in 2010, global energy production was primarily from coal (138 EJ), oil (171 EJ), and gas (106 EJ). With this policy, 2050 emissions are 42% less in our Base Policy case than our Reference case, although extending the scope of the carbon price to include emissions from land use change would reduce 2050 emissions by 52% relative to the same baseline. Our results from various policy scenarios show that lignocellulosic (LC) ethanol may become the major form of bioenergy, if its production costs fall by amounts predicted in a recent survey and ethanol blending constraints disappear by 2030; however, if its costs remain higher than expected or the ethanol blend wall continues to bind, bioelectricity and bioheat may prevail. Higher LC ethanol costs may also result in the expanded production of first-generation biofuels (ethanol from sugarcane and corn) so that they remain in the fuel mix through 2050. Deforestation occurs if emissions from land use change are not priced, although the availability of biomass residues and improvements in crop yields and conversion efficiencies mitigate pressure on land markets. As regions are linked via international agricultural markets, irrespective of the location of bioenergy production, natural forest decreases are largest in regions with the lowest barriers to deforestation. In 2050, the combination of carbon price and bioenergy production increases food prices by 3.2%-5.2%, with bioenergy accounting for 1.3%-3.5%. © 2015.
  • Authors:
    • Xu,X.
  • Source: Acta Scientiae Circumstantiae
  • Volume: 35
  • Issue: 8
  • Year: 2015
  • Summary: Farmland releases greenhouse gases, therefore is of great importance to climate change. Carbon footprint is an ideal method to evaluate comprehensive greenhouse gas emissions of crops through the entire life cycle. This study took Jinzhong City, Shanxi Province, a typical winter wheat planting area as an example. Carbon footprint of wheat production was calculated using life cycle assessment. Furthermore, carbon footprint was optimized based on nonlinear programming aiming at reducing carbon emission as well as increasing crop unit yield. Results showed that, after energy-based allocating, carbon footprint for 1000 kg wheat production was 1357.28 kg CO2 equivalent under traditional farm management. Two major phrases of carbon footprint generation were N2O emission from farmland and urea manufacture. Through altering the fertilizer amount and adjusting the ratio of urea and mature, carbon footprint of 1000 kg wheat production could be reduced to 469.99 kg CO2 equivalent, with 9.13% increase in unit yield. Carbon footprint of wheat production in Jinzhong City showed great difference with results from previous studies in China, which was most likely due to various fertilizer amounts and N2O emission coefficients in different studies. This study provides important information in integrated greenhouse gas emissions of wheat production and quantitative methods to decrease carbon emission and increase crop yield. ©, 2015, Science Press. All right reserved.