• Authors:
    • Buller,L. S.
    • Bergier,I.
    • Ortega,E.
    • Moraes,A.
    • Bayma-Silva,G.
    • Zanetti,M. R.
  • Source: Agricultural Systems
  • Volume: 137
  • Year: 2015
  • Summary: Greenhouse gas emissions and climate change has been partially attributed to agricultural expansion by deforestation, while the pressure to assure food, fiber and energy for the future generations leads to the intensification of agricultural systems. The transition to more efficient systems is actually considered an important strategy to reduce deforestation and to spare land for other uses, including the recovery of environmental services and ecohydrological processes in the drainage basin such as carbon sink and water regulation. The Brazilian Federal Program for Low Carbon Agriculture (ABC Program) intends to reduce carbon emissions by stimulating technological processes that neutralize emissions or enhance the sinking of greenhouse gases. A pilot farm has been established to assess an intensive animal-plant farming system that incorporates anaerobic digestion for biogas, power generation and organic fertilizer production. Emergy Synthesis was chosen as a methodological tool to assess and to diagnosis the farm system design. The modified emergy assessment including externalities (greenhouse gas emissions) improves the understanding of integrated crop-livestock systems efficiency in internal recycling of nutrients and power conversion. The adoption of manure treatment in intensified agricultural systems can effectively contribute to enhance environmental and economic performances.
  • Authors:
    • Fernandez-Llamazares,Alvaro
    • Elena Mendez-Lopez,Maria
    • Diaz-Reviriego,Isabel
    • McBride,Marissa F.
    • Pyhala,Aili
    • Rosell-Mele,Antoni
    • Reyes-Garcia,Victoria
  • Source: Climatic Change
  • Volume: 131
  • Issue: 2
  • Year: 2015
  • Summary: Indigenous societies hold a great deal of ethnoclimatological knowledge that could potentially be of key importance for both climate change science and local adaptation; yet, we lack studies examining how such knowledge might be shaped by media communication. This study systematically investigates the interplay between local observations of climate change and the reception of media information amongst the Tsimane', an indigenous society of Bolivian Amazonia where the scientific discourse of anthropogenic climate change has barely reached. Specifically, we conducted a Randomized Evaluation with a sample of 424 household heads in 12 villages to test to what degree local accounts of climate change are influenced by externally influenced awareness. We randomly assigned villages to a treatment and control group, conducted workshops on climate change with villages in the treatment group, and evaluated the effects of information dissemination on individual climate change perceptions. Results of this work suggest that providing climate change information through participatory workshops does not noticeably influence individual perceptions of climate change. Such findings stress the challenges involved in translating between local and scientific framings of climate change, and gives cause for concern about how to integrate indigenous peoples and local knowledge with global climate change policy debates.
  • Authors:
    • Fujisaki,K.
    • Perrin,A. S.
    • Desjardins,T.
    • Bernoux,M.
    • Balbino,L. C.
    • Brossard,M.
  • Source: Global Change BIology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: The impact of deforestation on soil organic carbon (SOC) stocks is important in the context of climate change and agricultural soil use. Trends of SOC stock changes after agroecosystem establishment vary according to the spatial scale considered, and factors explaining these trends may differ sometimes according to meta-analyses. We have reviewed the knowledge about changes in SOC stocks in Amazonia after the establishment of pasture or cropland, sought relationships between observed changes and soil, climatic variables and management practices, and synthesized the delta 13C measured in pastures. Our dataset consisted of 21 studies mostly synchronic, across 52 sites (Brazil, Colombia, French Guiana, Suriname), totalling 70 forest-agroecosystem comparisons. We found that pastures ( n=52, mean age=17.6 years) had slightly higher SOC stocks than forest (+6.83.1 %), whereas croplands ( n=18, mean age=8.7 years) had lower SOC stocks than forest (-8.52.9 %). Annual precipitation and SOC stocks under forest had no effect on the SOC changes in the agroecosystems. For croplands, we found a lower SOC loss than other meta-analyses, but the short time period after deforestation here could have reduced this loss. There was no clear effect of tillage on the SOC response. Management of pastures, whether they were degraded/nominal/improved, had no significant effect on SOC response. delta 13C measurements on 16 pasture chronosequences showed that decay of forest-derived SOC was variable, whereas pasture-derived SOC was less so and was characterized by an accumulation plateau of 20 Mg SOC ha -1 after 20 years. The large uncertainties in SOC response observed could be derived from the chronosequence approach, sensitive to natural soil variability and to human management practices. This study emphasizes the need for diachronic and long-term studies, associated with better knowledge of agroecosystem management.
  • Authors:
    • Hall,S. J.
    • Silver,W. L.
    • Timokhin,V. I.
    • Hammel,K. E.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia is thought to suppress lignin decomposition, yet potential effects of oxygen (O 2) variability in surface soils have not been explored. Here, we tested the impact of redox fluctuations on lignin breakdown in humid tropical forest soils during ten-week laboratory incubations. We used synthetic lignins labeled with 13C in either of two positions (aromatic methoxyl or propyl side chain C beta) to provide highly sensitive and specific measures of lignin mineralization seldom employed in soils. Four-day redox fluctuations increased the percent contribution of methoxyl C to soil respiration relative to static aerobic conditions, and cumulative methoxyl-C mineralization was statistically equivalent under static aerobic and fluctuating redox conditions despite lower soil respiration in the latter treatment. Contributions of the less labile lignin C beta to soil respiration were equivalent in the static aerobic and fluctuating redox treatments during periods of O 2 exposure, and tended to decline during periods of O 2 limitation, resulting in lower cumulative C beta mineralization in the fluctuating treatment relative to the static aerobic treatment. However, cumulative mineralization of both the C beta- and methoxyl-labeled lignins nearly doubled in the fluctuating treatment relative to the static aerobic treatment when total lignin mineralization was normalized to total O 2 exposure. Oxygen fluctuations are thought to be suboptimal for canonical lignin-degrading microorganisms. However, O 2 fluctuations drove substantial Fe reduction and oxidation, and reactive oxygen species generated during abiotic Fe oxidation might explain the elevated contribution of lignin to C mineralization. Iron redox cycling provides a potential mechanism for lignin depletion in soil organic matter. Couplings between soil moisture, redox fluctuations, and lignin breakdown provide a potential link between climate variability and the biochemical composition of soil organic matter.
  • Authors:
    • Oluwole,O. S. A.
  • Source: Climatic Change
  • Volume: 131
  • Issue: 2
  • Year: 2015
  • Summary: Konzo epidemics occur during droughts in East, Central, and Southern Africa, where the population depends almost exclusively on poorly processed cassava. Warm phases of El Nino-Southern Oscillation (ENSO) and Pacific decadal Oscillation (PDO) are associated with droughts in these areas of Africa, but with increase rainfall in South America. To further understanding of the relationship of droughts, cassava production, and konzo epidemics, this study was done to determine if there is coherence of spectra of ENSO, PDO and cassava production. Annual time series of cassava production in Tanzania and Brazil, multivariate ENSO index (MEI), and the Pacific Decadal Oscillation index (PDO) from 1961-2013 were compared. Wavelet and cross wavelet analyses of cassava production, ENSO, and PDO were performed. Warm phases of ENSO and PDO were associated with high cassava production in Tanzania, but with low cassava production in Brazil. Spectrogram of cassava showed significantly high production at periodicities of 3-9 years in Tanzania, but with significantly low production at periodicities of 2-6 years in Brazil. Cross wavelet spectrograms showed coherence of cassava production, ENSO and PDO in Tanzania and Brazil. Time-varying cyclical cassava production in Tanzania and Brazil are coupled to ENSO and PDO modes. Occurrence of droughts, high cassava production, and konzo epidemics in Tanzania are attributable to the impact of climate variability, which should be the focus of public health policies to control konzo epidemics.
  • Authors:
    • Prasad,J. V. N. S.
    • Rao,Ch S.
    • Ravichandra,K.
    • Jyothi,Ch N.
    • Babu,M. B. B. P.
    • Babu,V. R.
    • Raju,B. M. K.
    • Rao,B. B.
    • Rao,V. U. M.
    • Venkateswarlu,B.
    • Devasree Naik
    • Singh,V. P.
  • Source: Journal of Agrometeorology
  • Volume: 17
  • Issue: 1
  • Year: 2015
  • Summary: Carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2O) are important biogenic green house gases (GHGSs) from agricultural sector contributing to global warming. Temperature and rainfall play an important role in GHGS fluxes and information on their role in rainfed crops and systems is very scanty. Field studies were conducted at Hyderabad, India during 2012 rainy season to quantify GHGSs fluxes from two important food crops grown widely in rainfed regions viz. sorghum and pigeonpea. Quantum of fluxes ranged from 26-85 mg CO 2 - C m -2 h -1 in case of CO 2 and 18-68 g N 2O-N m -2 h -1 in case of N 2O at different stages of crop growth. Cumulative seasonal fluxes are 1.18 and 1.24 Mg CO 2-C ha -1 and 0.78 and 0.94 kg N 2O-N ha -1, in sorghum and pigeonpea, respectively. Ambient temperature and rainfall significantly influenced CO 2 fluxes. CO 2 fluxes increased with increase in temperature from 25.9°C to 31°C and fluxes were highest at 28.4°C in pigeonpea and at 27.7°C in sorghum. Quantum of CO 2 fluxes were highest at grain filling stage in sorghum and grand growth period in pigeonpea. N 2O fluxes increased with increase in temperature and moisture availability. These results provide evidence that rainfed crops in semi-arid regions contribute significant CO 2 and N 2O fluxes which are influenced by temperature and rainfall, thus warrant further studies.
  • Authors:
    • Apolinario,V. X. O.
    • Dubeux,J. C. B.
    • Lira,M. A.
    • Ferreira,R. L. C.
    • Mello,A. C. L.
    • Santos,M. V. F.
    • Sampaio,E. V. S. B.
    • Muir,J. P.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Warm-climate grasslands can be degraded by overgrazing and reduced soil fertility. However, legume trees integrated into these systems (silvopasture) can provide long-term marketable wood for sale and add N to the system. In addition, tree legumes can improve livestock diet by providing high crude protein forage. Our research assessed biomass and N accumulation by tree legumes: gliricidia [ Gliricidia sepium (Jacq.) Kunthe] and sabia ( Mimosa caesalpiniifolia Benth.) grown in conventionally grazed signal grass ( Brachiaria decumbens Stapf) pasture. The seedlings were planted in 2008 and growth rates were measured in 2012 and 2013. One year after the seedlings were planted, in July 2009, the pastures were grazed. Aboveground biomass doubled from 25 to 50 Mg ha -1 between February 2012 and August 2013. The thickest branches contributed the most ( p≤0.05) biomass: 58% for gliricidia and 54% for sabia. Leaves represented the smallest ( p≤0.05) fraction: 7 to 13% for gliricidia and 4 to 14% for sabia. Leaf and branch nutrient concentrations varied little ( p>0.05) between species and sampling periods. Gliricidia leaf N ranged from 33.6 to 38.0 g kg -1, while sabia leaf N ranged from 26.9 to 38.5 g kg -1. Biologically fixed N in leaves ranged from 30 to 121 kg ha -1. Sabia branches had less moisture and greater lignin, density, and gross calorific power than gliricidia. While thicker branches represent most of the aboveground tree biomass, leaves and thin branches have greater N concentration, representing an important return pathway to the soil.
  • Authors:
    • Dold,Christian
    • Becker,Mathias
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 178
  • Issue: 4
  • Year: 2015
  • Summary: Lake Naivasha is a freshwater lake in the East African Rift Valley. With continued lake level declines between 1980 and 2011, the newly exposed land areas were gradually taken for agricultural use. The resulting chronosequences allow for an analysis of the effects of land use duration on nutrient dynamics and agricultural production. Transects representing land use durations of 0-30 (cropland) and 15-30 years (pasture) were established on soils formed on alluvial deposits and lacustrine sediments. We assessed changes in topsoil nitrogen (N) stocks (t ha(-1)), ammonium mineralization potential (N-supplying capacity), and plant-available P with increasing durations of land use. An additional greenhouse experiment studied the responses of kikuyu grass (Cenchrus clandestinus) and maize (Zea mays) in potted topsoil collected from differnt land-use types and chronosequence positions. With increasing duration of land use we noted a significant decline (P < 5%) in soil N contents under both pasture and cropland uses, following a model of exponential decay. The N stocks decreased at 84kgha(-1) a(-1) and a decay rate constant of 0.019a(-1) in pasture soil within 15 years, and at 75kgha(-1) a(-1) with a decay rate-constant of 0.013 a(-1) in cropland soil within 30 years. While the ammonium-N mineralization potential also decreased with land use duration, the trends were significant only in lacustrine pasture soils. Plant-available P did not show any trends that were related to the duration of land use. Kikuyu grass and maize accumulated less dry matter and N as the duration of use increased. This biomass accumulation was significantly related to soil N. A continued mineralization of soil organic matter has possibly contributed to the observed soil N depletion over time. The continuous agricultural use of the littoral wetland zone of Lake Naivasha is likely to entail declining production potentials for both pastures and food crops.
  • Authors:
    • Ogwang, F.
    • Karungi, J.
    • Lederer, J.
  • Source: Journal of Agriculture
  • Volume: 207
  • Year: 2015
  • Summary: Like many other countries in Sub-Saharan Africa (SSA), Uganda faces a remarkable soil nutrient deficit in farmland soils. In order to cope with this deficit, many authors suggest increasing the recycling of hitherto unused nutrient sources from human excrement and urban municipal solid waste (MSW). However, a quantification of the potential of these nutrient sources to overcome soil nutrient deficits in Uganda has not been carried out so far. This research paper presents a case study calculating the soil nutrient balance for nitrogen (N), phosphorus (P), and potassium (K), as well as the potential of hitherto unused human excrement and urban MSW to decrease soil nutrient deficits in agricultural land by applying the method of material flow analysis (MFA) in Busia District (Uganda). Results show a high soil nutrient deficit of agricultural soils in the district, with values of -33 kg N ha -1, -6 kg P ha -1, and -41 kg K ha -1. The potential to reduce these negative balances is negligible for hitherto unused urban MSW (1-3%), but higher for human excrement (17-60%). The low potential of urban MSW as well as the hygienic problems associated with human excrement (particularly feces) means that other measures such as soil conservation and mineral fertilizer application should not be ignored in the effort to increase agricultural productivity. This is not only valid for Busia District, but also for other regions in SSA.
  • 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.