• Authors:
    • Damerau,Kerstin
    • van Vliet,Oscar P. R.
    • Patt,Anthony G.
  • Source: Climatic Change
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: The Middle East and North Africa (MENA) region stands out globally both for the immensity of its energy resources, and the paucity of its freshwater resources. Most energy extraction and conversion technologies have associated freshwater demand, and in the MENA region these account for 2 % of the available sustainable supply. We examine how this demand could change over the 21st century, assuming growth in population and economic output, and considering three alternative pathways for energy efficiency, carbon intensity, and energy exports from the region. We find that in the pathway marked by improved efficiency, a transition to renewable energy sources, and declining energy exports, water consumption for energy is twice as high as today's values by the end of the century. By contrast, in the pathway marked by continued commitment to fossil resource extraction, use, and export, water demand for energy might rise by a factor of five. If the region were to maintain high levels of energy exports, but would substitute the export of fossil fuels by an equivalent amount of electricity derived from sunlight, a freshwater volume comparable to the household needs of up to 195 million people could be saved.
  • Authors:
    • Aziz, S. A.
    • Gong, P.
    • Hansen, M.
    • Justice, C.
    • Becker-Reshef, I.
    • Herrero, M.
    • Wood-Sichra, U.
    • Thornton, P.
    • Mosnier, A.
    • Havlik, P.
    • Perger, C.
    • Schill, C.
    • Albrecht, F.
    • Duerauer, M.
    • Moltchanova, E.
    • Bun, A.
    • You, L.
    • McCallum, I.
    • See, L.
    • Fritz, S.
    • Cipriani, A.
    • Cumani, R.
    • Cecchi, G.
    • Conchedda, G.
    • Ferreira, S.
    • Gomez, A.
  • Source: Journal Article
  • Volume: 21
  • Issue: 5
  • Year: 2015
  • Summary: A new 1 km global IIASA-IFPRI cropland percentage map for the baseline year 2005 has been developed which integrates a number of individual cropland maps at global to regional to national scales. The individual map products include existing global land cover maps such as GlobCover 2005 and MODIS v.5, regional maps such as AFRICOVER and national maps from mapping agencies and other organizations. The different products are ranked at the national level using crowdsourced data from Geo-Wiki to create a map that reflects the likelihood of cropland. Calibration with national and subnational crop statistics was then undertaken to distribute the cropland within each country and subnational unit. The new IIASA-IFPRI cropland product has been validated using very high-resolution satellite imagery via Geo-Wiki and has an overall accuracy of 82.4%. It has also been compared with the EarthStat cropland product and shows a lower root mean square error on an independent data set collected from Geo-Wiki. The first ever global field size map was produced at the same resolution as the IIASA-IFPRI cropland map based on interpolation of field size data collected via a Geo-Wiki crowdsourcing campaign. A validation exercise of the global field size map revealed satisfactory agreement with control data, particularly given the relatively modest size of the field size data set used to create the map. Both are critical inputs to global agricultural monitoring in the frame of GEOGLAM and will serve the global land modelling and integrated assessment community, in particular for improving land use models that require baseline cropland information. These products are freely available for downloading from the http://cropland.geo-wiki.org website.
  • Authors:
    • Freycon, V.
    • Laumonier, Y.
    • Locatelli, B.
    • Labriere, N.
    • Bernoux, M.
  • Source: Agricultural Journal
  • Volume: 203
  • Year: 2015
  • Summary: Healthy soils provide a wide range of ecosystem services. But soil erosion (one component of land degradation) jeopardizes the sustainable delivery of these services worldwide, and particularly in the humid tropics where erosion potential is high due to heavy rainfall. The Millennium Ecosystem Assessment pointed out the role of poor land-use and management choices in increasing land degradation. We hypothesized that land use has a limited influence on soil erosion provided vegetation cover is developed enough or good management practices are implemented. We systematically reviewed the literature to study how soil and vegetation management influence soil erosion control in the humid tropics. More than 3600 measurements of soil loss from 55 references covering 21 countries were compiled. Quantitative analysis of the collected data revealed that soil erosion in the humid tropics is dramatically concentrated in space (over landscape elements of bare soil) and time (e.g. during crop rotation). No land use is erosion-prone per se, but creation of bare soil elements in the landscape through particular land uses and other human activities (e.g. skid trails and logging roads) should be avoided as much as possible. Implementation of sound practices of soil and vegetation management (e.g. contour planting, no-till farming and use of vegetative buffer strips) can reduce erosion by up to 99%. With limited financial and technical means, natural resource managers and policy makers can therefore help decrease soil loss at a large scale by promoting wise management of highly erosion-prone landscape elements and enhancing the use of low-erosion-inducing practices.
  • Authors:
    • Kanninen, M.
    • Negash, M.
  • Source: Article
  • Volume: 203
  • Year: 2015
  • Summary: The fifth assessment report of the intergovernmental panel on climate change (IPCC) estimated that by 2040 agroforestry would offer high potential of carbon (C) sequestration in developing countries. However, the role of tropical agroforestry in C sequestration and in climate change mitigation has only recently been recognized by United Nations Framework Convention on Climate Change (UNFCCC). This is partly due to the lack of reliable estimates on the sequestration potential in biomass and soil carbon pools over time. The aim of this study was to analyze the changes in the biomass and soil carbon pools of three indigenous agroforestry systems in south-eastern Rift Valley escrapment of Ethiopia using CO2FIX (v. 3.2) model. The agroforestry systems studied were Enset ( Ensete ventricosum)-tree, Enset-coffee-tree, and Tree-coffee systems. To run the model, empirical data collected from 60 farms (20 farms for each agroforestry system) and literature were used as inputs to parameterize the model. Simulations were run over a period of 50 years. Average simulated total biomass C stocks was the highest for Tree-coffee system (122 Mg C ha -1), followed by the Enset-coffee-tree (114 Mg C ha -1) and Enset-tree system (76 Mg C ha -1). The tree cohort accounted for 89-97% of the total biomass C stocks in all the studied systems, and the reminder was shared by Enset and coffee cohorts. The total average simulated total C stocks (biomass and soil) were 209, 286 and 301 Mg C ha -1 for Enset-tree, Enset-coffee-tree and Tree-coffee systems, respectively. The soil organic carbon (SOC) stocks accounted for 60-64% of the total carbon in the studied systems. Model validation results showed that long-term (10-40 years) simulated biomass C stocks were within the range of measured biomass C stocks for Enset-tree and Enset-coffee-tree systems, but significantly differed for the Tree-coffee system. The simulated soil and total C stocks were within the range of measured values for all the three systems. The CO2FIX model accurately predicted the SOC and total C stocks in the studied indigenous agroforestry systems, but the prediction of the biomass C stocks could be improved by acquiring more accurate input parameter values for running the model.
  • Authors:
    • Lobell, D.
    • Abelleyra, D.
    • Veron, S.
  • Source: Article
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: Understanding regional impacts of recent climate trends can help anticipate how further climate change will affect agricultural productivity. We here used panel models to estimate the contribution of growing season precipitation (P), average temperature (T) and diurnal temperature range (DTR) on wheat, maize and soy yield and yield trends between 1971 and 2012 from 33 counties of the Argentine Pampas. A parallel analysis was conducted on a per county basis by adjusting a linear model to the first difference (i.e., subtracting from each value the previous year value) in yield and first difference in weather variables to estimate crop sensitivity to interannual changes in P, T, and DTR. Our results show a relatively small but significant negative impact of climate trends on yield which is consistent with the estimated crop and county specific sensitivity of yield to interannual changes in P, T and DTR and their temporal trends. Median yield loss from climate trends for the 1971-2012 period amounted to 5.4 % of average yields for maize, 5.1 % for wheat, and 2.6 % for soy. Crop yield gains for this time period could have been 15-20 % higher if climate remained without directional changes in the Pampas. On average, crop yield responded more to trends in T and DTR than in P. Translated into economic terms the observed reductions in maize, wheat, and soy yields due to climate trends in the Pampas would equal $1.1 B using 2013 producer prices. These results add to the increasing evidence that climate trends are slowing yield increase.
  • Authors:
    • Chang, J.
    • Cheng, J.
    • Peng, C.
    • Yang, G.
    • Ren, Y.
    • Gu, B.
    • Liu, D.
    • Wang, Y.
    • Ge, Y.
    • Wu, X.
  • Source: Journal of Cleaner Production
  • Volume: 95
  • Year: 2015
  • Summary: It is still controversial as to whether intensive agriculture increases or decreases carbon emissions compared to conventional farming. Carbon flux changes induced by the conversion of agricultural practices in different climatic regions have long been a scientific focus. As an intensive cultivation practice, vegetable cultivation within plastic greenhouses (PGVC) has been reported to reduce net carbon emissions following the conversion from conventional vegetable cultivation (CVC). However, it remains uncertain to what degree the carbon flux changes following the conversion in different climatic regions. Based on 637 paired soil data points and 189 vegetable data points from five major climatic regions in China, we used a full carbon cycle analysis to estimate the carbon flux changes when converting from CVC to PGVC. Results showed that the conversion reduced net carbon emissions in four climatic regions (middle temperate, warm temperate, south subtropical and north subtropical regions) but increased net carbon emissions in the Tibet Plateau region. This regional variation was attributable to the differences between soil carbon sequestration and fossil fuel emissions. The highest reduction (1.46 Mg C ha(-1) yr(-1)) occurred in the middle temperate region while the Tibet Plateau region acted as a net carbon source (-0.24 Mg C ha(-1) yr(-1)). This suggests that the conversion can increase carbon benefits within the four climatic regions. PGVC in these regions could be considered as a promising option for carbon-smart intensive agriculture and would be worth expanding in countries with similar weather conditions, to mitigate carbon emissions. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Ladoni,M.
    • Basir,A.
    • Kravchenko,A.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 3
  • Year: 2015
  • Summary: Active fractions of soil C such as particulate organic C (POC) and short-term mineralizable C (SMC) respond faster than total organic C (TOC) to management induced changes in soil C. However, the active fractions of organic C can possibly have larger variability that decreases the detectability of management effects on soil C. The objectives of this study were to (i) assess the relative usefulness of TOC, POC, and SMC as criteria of management induced changes on soil C and (ii) investigate if using auxiliary soil and topographical information can aid in increasing the usefulness of these criteria in studies conducted across large spatial scales. Data were collected at locations with two contrasting topographical positions (slope and depression) within 10 agricultural fields in conventional and cover crop based row crop managements at the 0- to 20-, 35- to 50-, and 70- to 90-cm depths. The results showed that to detect differences between the management systems with an acceptable type II error of 0.20, an 80% difference in TOC and a 50% difference in SMC were needed. The statistical power for POC was never in an acceptable range. The use of auxiliary soil and topography information via analysis of covariance decreased the sizes of the minimal detectable differences. Given the faster reaction to management of SMC as compared with TOC, and its lower variability as compared with POC, we recommend SMC as the preferred C fraction for detecting treatment induced differences in organic C stocks in agricultural field experiments, especially in deeper soil layers. © Soil Science Society of America, 5585 Guilford Rd., Madison Wl 53711 USA.
  • Authors:
    • Lal,Rattan
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 3
  • Year: 2015
  • Authors:
    • Messerli,J.
    • Bertrand,A.
    • Bourassa,J.
    • Belanger,G.
    • Castonguay,Y.
    • Tremblay,G.
    • Baron,V.
    • Seguin,P.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: The increase in atmospheric carbon dioxide concentration ([CO 2]) and consequent increase in air temperature is expected to have significant effects on plant growth and nutritive value. Studies examining the effects of elevated [CO 2] on plants under field conditions have been limited by the inherent difficulty to modify air composition in open air. Here we describe an efficient and inexpensive open-top chamber (OTC) system designed to study the effects of elevated atmospheric [CO 2] and temperature on perennial alfalfa-timothy ( Medicago sativa L.)-( Phleum pratense L.) mixture. The design and construction of these OTCs are described in detail, along with cost estimation for each component. Eight OTCs, each with 1.2 m 2 of ground area (four with elevated [CO 2] and four with ambient [CO 2]) were fabricated and four control plots of the same dimension were established to assess the chamber effects on plant responses to CO 2. The [CO 2] in elevated-CO 2 chambers fell 93% of the time within 20% of the targeted 600 mol mol -1 CO 2, based on 10 min averages. The CO 2 consumption in elevated-CO 2 chambers averaged 3.0 kg CO 2 m -2 d -1. To ensure that the environment within OTCs was similar to the surrounding field, growing conditions were determined in all chambers and control plots. Adequate light transmission was observed compared to control plots (93%) and the temperature increase was 0.7°C on average. After two growing seasons of continued use, this system has proven its effectiveness for studying the effects of CO 2 and climate change in the field at low cost.
  • Authors:
    • Miglierina,A. M.
    • Iglesias,J. O.
    • Laurent,G. C.
    • Rodriguez,R. A.
    • Ayastuy,M. E.
    • Lobartini,J. C.
  • Source: Acta Horticulturae
  • Volume: 1076
  • Issue: 1076
  • Year: 2015
  • Summary: The application of composted organic wastes to soil can be used for conserving soil organic matter, reclaiming degraded soils and supplying plants with nutrients. Two greenhouse experiments were carried out to evaluate the addition of compost on chemical and physical properties of soils. Four different texture soils were used: Sandy soil (S1), Silty loam soil (S2), Clay loam soil (S3) (33.2 O.C. g.kg -1) and Clay loam soil (S4) (14.8 O.C. g.kg -1) cultivated with lettuce ( Lactuca sativa L.) in the Bahia Blanca region, Argentina. The application of compost had a significant effect on lettuce productivity and nutrient uptake by the crop in three of the four soil types; showing a positive effect on the dry weight, number, length and width of the leaves. The applied dose (40 Mg ha -1) modified the chemical composition of the plants: those grown in soil with added compost showed higher concentrations of nutrients than those grown in control soils. In clay loam soil (S3) no difference were found in plant productivity between treatments with and without application of compost. With respect to soil properties changes, the application of compost affected the soil pH in variable way; increased organic carbon, total nitrogen and available phosphorus. The addition of compost lowered bulk density in soils S2 and S4; increased the percentage of macropores and mesopores in S2; diminished content of mesopores and increased content of micropores at S3 and S4. The variations on chemical and physical soil properties demonstrate the benefits of compost addition, even in a short period of time.