• Authors:
    • Amadi, C. N.
    • Nduka, J. K.
    • Orisakwe, O. E.
    • Dike, D. O.
    • Bede, O.
  • Source: Chemistry Central Journal
  • Volume: 6
  • Issue: 77
  • Year: 2012
  • Summary: Background: This study assessed lead, cadmium, and nickel level in food crops, fruits and soil samples from Ohaji and Umuagwo and Owerri in South Eastern Nigeria and estimated the potential health risks of metals. Samples were washed, oven-dried at 70-80°C for 24 h and powdered. Samples were digested with perchloric acid and nitric acid. Metals were analysed with Unicam Atomic Absorption Spectrophotometer. Result: The concentration of Pb, Cd, and Ni in Ohaji exceeded the maximum allowable concentrations for agricultural soil as recommended by EU. Lead, Cd, and Ni in the food crops were highest in Oryza sativa, Glycine max, and Pentabacta microfila respectively. Highest levels of Pb, Cd, and Ni, in fruits were detected in Canarium schweinfurthii, Citrus reticulata, Ananas comosus respectively. The true lead and cadmium intake for the rice based meal were 3.53 and 0.034 g/kg respectively. Whereas the true intake of lead and cadmium for the cassava based meal were 19.42 and 0.049 g/kg respectively. Conclusion: Local food stuff commonly available in South Eastern Nigeria villages may contribute to the body burden of heavy metal. This is of public health importance.
  • Authors:
    • Healey, J.
    • Attarzadeh, N.
    • Soto, G.
    • Haggar, J.
    • Edwards-Jones, G.
    • Noponen, M.
  • Source: Agriculture Ecosystems & Environment
  • Volume: 151
  • Year: 2012
  • Summary: Coffee plays a key role in sustaining millions of livelihoods around the world. Understanding GHG emissions from coffee supply chains is important in evaluating options for climate change mitigation within the sector. We use data from two long-term coffee agroforestry experiments in Costa Rica and Nicaragua to calculate carbon footprints (CF) for coffee and identify emission hotspots within different management systems, levels of inputs and shade types. Management system and input level were the main cause of variation in CFs. Carbon footprints for 1 kg of fresh coffee cherries were between 0.26 and 0.67 kgCO(2)e for conventional and 0.12 and 0.52 kgCO(2)e for organic management systems. The main contributor to GHG emissions for all management systems was the inputs of organic and inorganic nitrogen. Nitrous oxide emissions from pruning inputs contributed between 7% and 42% of CFs. However, these estimates were strongly influenced by the choice of emission factor used in the calculations. Research is required to develop emission factors that account for different qualities and management of nitrogen inputs to enable effective calculation of the CF from different management strategies, and especially from the pruning and organic inputs managed in agroforestry systems. As such, effective climate change mitigation strategies can only be developed from site-specific studies which utilise accurate accounting and regional-specific emission factors. (c) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Potvin, C.
    • Codjia, C.
    • Pelletier, J.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 12
  • Year: 2012
  • Summary: Reducing emissions from deforestation and forest degradation (REDD+) requires developing countries to quantify greenhouse gas emissions and removals from forests in a manner that is robust, transparent, and as accurate as possible. Although shifting cultivation is a dominant practice in several developing countries, there is still very limited information available on how to monitor this land-use practice for REDD+ as little is known about the areas of shifting cultivation or the net carbon balance. In this study, we propose and test a methodology to monitor the effect of the shifting cultivation on above-ground carbon stocks. We combine multiyear remote sensing information, taken from a 12-year period, with an in-depth community forest carbon stock inventory in Palo Seco Forest Reserve, western Panama. Using remote sensing, we were able to separate four forest classes expressing different forest-use intensity and time-since-intervention, which demonstrate expected trends in above-ground carbon stocks. The addition of different interventions observed over time is shown to be a good predictor, with remote sensing variables explaining 64.2% of the variation in forest carbon stocks in cultivated landscapes. Multitemporal and multispectral medium-resolution satellite imagery is shown to be adequate for tracking land-use dynamics of the agriculture-fallow cycle. The results also indicate that, over time, shifting cultivation has a transitory effect on forest carbon stocks in the study area. This is due to the rapid recovery of forest carbon stocks, which results in limited net emissions. Finally, community participation yielded important additional benefits to measuring carbon stocks, including transparency and the valorization of local knowledge for biodiversity monitoring. Our study provides important inputs regarding shifting cultivation, which should be taken into consideration when national forest monitoring systems are created, given the context of REDD+ safeguards.
  • Authors:
    • Vindas, L.
    • Urena, N.
    • Dietsch, T.
    • Castro-Tanzi, S.
    • Chandler, M.
  • Source: Agricultural Ecosystems & Enviroment
  • Volume: 155
  • Year: 2012
  • Summary: Many coffee agroecosystems in Latin America have been transformed with the goal of maximizing yields. In these intensively managed farming systems, inorganic fertilizers are commonly used, with important agronomic, economical and ecological consequences. This study reviews the relationship between fertilizer application, coffee yield and quality indicators and soil chemical properties in coffee farms of the Los Santos region in Costa Rica. The mean nitrogen (N) input rate in farms employing inorganic fertilizer was 21216.7 kg ha -1 y -1. Yield reported by farmers had a positive marginally significant relationship with nutrient application rates. Cup quality attribute responded positively to calcium oxide (CaO) applications. Variables related to production and quality indicators were number of fungicide applications, soil exchangeable calcium (Ca) and acidity, elevation of the terrain, and number of stems per plant. Soil exchangeable Ca was positively correlated with the ratio of crop yield per unit of applied N fertilizer. In those farms with higher N input rates, soil pH was significantly lower. We suggest that the N saturation hypothesis developed for temperate forests under N atmospheric deposition is applicable to this perennial agroecosystem. This hypothesis predicts changes in the soil chemistry and nutrient retention capacity, and a reduction of Net Primary Productivity (NPP).
  • Authors:
    • Tivet, F.
    • Khamxaykhay, C.
    • Rattanatray, B.
    • Jullien, F.
    • Quoc, H. T.
    • Lestrelin, G.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 1
  • Year: 2012
  • Summary: Over the past half-century, major efforts have been made worldwide to develop sustainable alternatives to agricultural tillage. In line with these efforts, two main research development initiatives have supported the experimentation and dissemination of conservation agriculture (CA) in Laos. Here we present the results of a 4-year monitoring and evaluation study conducted in 21 villages targeted for dissemination. In a context of rapid transition to intensive commercial agriculture in Laos, CA has become an important constituent of agricultural landscapes. However, there are significant variations in adoption rates across the study region. Statistical and qualitative evidence suggests that experimentation and adoption are not contingent upon farm-level variables such as capital, labor, age and education. While access to land helps shape local decision-making, the land tenure threshold under which farmers are not willing to experiment with alternative cropping systems is relatively low and highly variable in both space and time. Rather, experience and awareness of land degradation, production costs, social cohesion and leadership appear to be key factors in explaining most variations in local adoption rates. These results indicate that the practice of CA is not necessarily incompatible with smallholder farming. However, while complex crop associations and rotations are necessary for integrated weed control and reduced chemical use, their diffusion would require a broader transformation of the agricultural industry and the current market demand.
  • Authors:
    • Lakshmanan, P.
    • Robinson, N.
    • Brackin, R.
    • Holst, J.
    • Schmidt, S.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 155
  • Year: 2012
  • Summary: Addressing the limited knowledge of nitrogen (N) pools in tropical agricultural soils and the need to reduce N losses from these systems, we analysed soluble organic and inorganic N in two Hydrosols under sugarcane. Concentrations of ammonium and nitrate spanned ~3 - orders of magnitude (0.2-41.0 mg ammonium-N, 0-10.7 mg nitrate-N kg -1 soil) with the highest concentrations detected within 2-3 months of fertiliser application. Soluble amino acids spanned 1-order of magnitude (0.22-2.42 mg amino acid-N kg -1 soil) and accounted for up to 70% of the low-molecular weight N. Amino acid concentrations were usually highest in the wet season and uniform across soil depth, indicating that amino acids are generated throughout the studied profile. We compared soluble and dissolved (free) N in the soil solution in a subset of samples. In soil solution, amino acid, ammonium and nitrate concentrations averaged 20, 265 and 1820 M, respectively, corresponding to ~10% (amino acids), ~20% (ammonium) and ~100% (nitrate) of the soluble N pool. We calculated an annual gross amino acid flux in the dissolved N pool in the order of 2-6 tons N ha -1 yr -1 in the upper 40 cm of soil. We discuss whether amino acids can significantly contribute to the N demand of sugarcane.
  • Authors:
    • Roy-Macauley, H.
    • Jalloh, A.
    • Sereme, P.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 157
  • Year: 2012
  • Summary: The West and Central Africa (WCA) sub region covers a total area of over 11.5 million km 2 with a population of over 318 million. Most of the rural population in WCA are poor and food insecure and about 70% of the people in the region depends on agriculture, which accounts for over 35% of Gross Domestic Product (GDP) and over 40% of its export. The agroecological zones of WCA are closely related to the agro climatic zones of the region with rainfall decreasing from the southern coast in the forest region to the sub humid and semi arid Sahelian region in the north. The major agroecosystems of WCA include the semi arid, sub humid, humid forest, and swamp. Growing populations, inappropriate agricultural practices and changing climate in the region are influencing the composition and ability of agroecosystems in providing much needed ecosystem services. Coordinating efforts to tackle these challenges and leverage opportunities for sustainable agricultural production while ensuring conservation of the diverse ecosystems in the region is therefore a major preoccupation of the West and Central African Council for Agricultural Research and Development (CORAF/WECARD).
  • Authors:
    • Compaore, H.
    • Hien, F.
    • Djagbletey, G.
    • Veenendaal, E.
    • Feldpausch, T. R.
    • Schwarz, M.
    • Schrodt, F.
    • Domingues, T.
    • Bird, M. I.
    • Saiz, G.
    • Diallo, A.
    • Lloyd, J.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 8
  • Year: 2012
  • Summary: We examine the influence of climate, soil properties and vegetation characteristics on soil organic carbon (SOC) along a transect of West African ecosystems sampled across a precipitation gradient on contrasting soil types stretching from Ghana (15°N) to Mali (7°N). Our findings derive from a total of 1108 soil cores sampled over 14 permanent plots. The observed pattern in SOC stocks reflects the very different climatic conditions and contrasting soil properties existing along the latitudinal transect. The combined effects of these factors strongly influence vegetation structure. SOC stocks in the first 2 m of soil ranged from 20 Mg C ha -1 for a Sahelian savanna in Mali to over 120 Mg C ha -1 for a transitional forest in Ghana. The degree of interdependence between soil bulk density (SBD) and soil properties is highlighted by the strong negative relationships observed between SBD and SOC ( r2>0.84). A simple predictive function capable of encompassing the effect of climate, soil properties and vegetation type on SOC stocks showed that available water and sand content taken together could explain 0.84 and 0.86 of the total variability in SOC stocks observed to 0.3 and 1.0 m depth respectively. Used in combination with a suitable climatic parameter, sand content is a good predictor of SOC stored in highly weathered dry tropical ecosystems with arguably less confounding effects than provided by clay content. There was an increased contribution of resistant SOC to the total SOC pool for lower rainfall soils, this likely being the result of more frequent fire events in the grassier savannas of the more arid regions. This work provides new insights into the mechanisms determining the distribution of carbon storage in tropical soils and should contribute significantly to the development of robust predictive models of biogeochemical cycling and vegetation dynamics in tropical regions.
  • Authors:
    • Chidthaisong, A.
    • Lu, Y.
    • Yuan, Q.
    • Klose, M.
    • Conrad, R.
  • Source: Soil Biology and Biochemistry
  • Volume: 49
  • Issue: June
  • Year: 2012
  • Summary: Straw amendment is a common practice for improving the fertility of rice field soils, but it also enhances production of the greenhouse gas methane. To quantify carbon flux partitioning and priming effects due to straw amendment, we measured delta C-13 in CH4 and CH4 precursors produced in anoxic slurries of soil from Italy, China and Thailand after addition of straw from either rice (C3 plant) or maize plants (C4 plant), which have different delta C-13 signatures. The delta C-13 values of the CH4, acetate and CO2 produced were similar when expressed as the difference to the delta C-13 value of the straw applied. These results indicated that the C-13-isotopic fractionation involved in methanogenic decomposition was similar for rice straw and maize straw. However, measurement of CH4 produced in soil without or with straw showed that isotopic fractionation during methanogenic degradation of straw was smaller than during degradation of soil organic matter. Isotopic fractionation during hydrogenotrophic methanogenesis, measured in the presence of methyl fluoride, with straw was also smaller than with soil organic matter. The results show that C-13-isotopic analysis after application of rice straw and maize straw is a convenient approach for quantifying carbon flux partitioning during methanogenic degradation of straw and soil organic matter. In our experiments, straw degradation accounted for most of the CH4 production and caused a negative priming effect on the methanogenic degradation of soil organic matter. (c) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Hastings, A.
    • Sim, S.
    • King, H.
    • Keller, E.
    • Canals, L. M. I.
    • Flynn, H. C.
    • Wang, S.
    • Smith, P.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 5
  • Year: 2012
  • Summary: Many assessments of product carbon footprint (PCF) for agricultural products omit emissions arising from land-use change (LUC). In this study, we developed a framework based on IPCC national greenhouse gas inventory methodologies to assess the impacts of LUC from crop production using oil palm, soybean and oilseed rape as examples. Using ecological zone, climate and soil types fromnatural the top 20 producing countries, calculated emissions for transitions from vegetation to cropland on mineral soils under typical management ranged from -4.5 to 29.4 t CO2-eq ha-1 yr-1 over 20 years for oil palm and 1.247.5 t CO2-eq ha-1 yr-1 over 20 years for soybeans. Oilseed rape showed similar results to soybeans, but with lower maximum values because it is mainly grown in areas with lower C stocks. GHG emissions from other land-use transitions were between 62% and 95% lower than those from natural vegetation for the arable crops, while conversions to oil palm were a sink for C. LUC emissions were considered on a national basis and also expressed per-tonne-of-oil-produced. Weighted global averages indicate that, depending on the land-use transition, oil crop production on newly converted land contributes between -3.1 and 7.0 t CO2-eq t oil production-1 yr-1 for palm oil, 11.950.6 t CO2-eq t oil production-1 yr-1 for soybean oil, and 7.731.4 t CO2-eq t oil production-1 yr-1 for rapeseed oil. Assumptions made about crop and LUC distribution within countries contributed up to 66% error around the global averages for natural vegetation conversions. Uncertainty around biomass and soil C stocks were also examined. Finer resolution data and information (particularly on land management and yield) could improve reliability of the estimates but the framework can be used in all global regions and represents an important step forward for including LUC emissions in PCFs.