• 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:
    • Silva, B. P. da
    • Oliveira, F. de A.
    • Carvalho, C. J. R. de
    • Lucotte, M.
    • Davidson, R.
    • Comte, I.
    • Rousseau, G. X.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 156
  • Issue: 108-115
  • Year: 2012
  • Summary: Over a century, subsistence agriculture has been practiced in the Brazilian Amazon, using slash-and-burn as a traditional land clearing technique. However, fire clearing leads to nutrient losses, and the increasing demographic pressure reduces the duration of the fallow period, threatening the system sustainability. The chop-and-mulch land clearing method, combined or not with legume-enriched fallow, is a promising alternative technique as the retention of organic residues upon land clearance of fallow could promote soil fertility. The aim of this study is to assess the effect of fire-free land preparation on soil physicochemical properties by comparing the effects of traditional slash-and-burn with (i) chop-and mulch with enriched fallow in croplands and (ii) chop-and-mulch without enriched fallow in pastures. The chop-and-mulch of a legume-enriched fallow conserved soil bulk density, and significantly increased nutrient concentrations and organic matter content compared to the burnt cropland and the control forest. In the pastures, the use of chop-and-mulch of a non-enriched fallow had less impact on soil physical and chemical properties, excepted on water retention capacity and total P stock. Land clearing of fallows by chop-and-mulch, especially when enriched with legumes could significantly improve agriculture sustainability in the region and reduce the pressure on primary forests.
  • 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:
    • Neufeldt, H.
    • Coe, R.
    • Mwangi, P.
    • Jamnadass, R.
    • Muthuri, C.
    • Dietz, J.
    • Kuyah, S.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 158
  • Year: 2012
  • Summary: The high heterogeneity and diverse management effects on trees in agricultural landscapes limit the use of standard allometric equations developed for forests; hence the need to develop robust allometric equations and root:shoot ratios (RS) for more accurate estimation of belowground biomass. Local generic equations were developed from 72 trees (diameter at breast height (dbh): 3-102 cm) destructively sampled across three 100 km 2 benchmark sites in Western Kenya. Belowground biomass of the harvested trees accounted for about 20% of the total tree biomass; yielding an overall RS of 0.26, which varied across an altitudinal and precipitation gradient. The equation based on dbh alone estimated belowground biomass carbon in agricultural mosaics of Western Kenya to be 50.01 Mg C ha -1 with about 90% accuracy. Two of the equations recommended for tropical species produced estimates that were about 35 and 21% lower. The equation with dbh as predictor is therefore reliable for estimating belowground biomass in agricultural landscapes while RS should be used with great care depending on soil and management conditions as shown by the great variability among the blocks evaluated. Equations presented in this study will significantly improve the accuracy of root biomass estimates in agricultural landscape mosaics without the high investments in excavating the root system.
  • 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:
    • Kansiime, F.
    • Saunders, M. J.
    • Jones, M. B.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 4
  • Year: 2012
  • Summary: Tropical wetlands have been shown to exhibit high rates of net primary productivity and may therefore play an important role in global climate change mitigation through carbon assimilation and sequestration. Many permanently flooded areas of tropical East Africa are dominated by the highly productive C 4 emergent macrophyte sedge, Cyperus papyrus L. (papyrus). However, increasing population densities around wetland margins in East Africa are reducing the extent of papyrus coverage due to the planting of subsistence crops such as Colocasia esculenta (cocoyam). In this paper, we assess the impact of this land use change on the carbon cycle and in particular the impacts of land conversion on net ecosystem carbon dioxide exchange. Eddy covariance techniques were used, on a campaign basis, to measure fluxes of carbon dioxide over both papyrus and cocoyam dominated wetlands located on the Ugandan shore of Lake Victoria. Peak rates of net photosynthetic CO 2 assimilation, derived from monthly diurnal averages of net ecosystem exchange, of 28-35 mol CO 2 m -2 s -1 and 15-20 mol CO 2 m -2 s -1 were recorded in the papyrus and cocoyam wetlands, respectively, whereas night-time respiratory losses ranged between 10 and 15 mol CO 2 m -2 s -1 at the papyrus wetland and 5-10 mol CO 2 m -2 s -1 at the cocoyam site. The integration of the flux data suggests that papyrus wetlands have the potential to act as a sink for significant amounts of carbon, in the region of 10 t C ha -1 yr -1. The cocoyam vegetation assimilated ~7 t C ha -1 yr -1 but when carbon exports from crop biomass removal were accounted for these wetlands represent a significant net loss of carbon of similar magnitude. The development of sustainable wetland management strategies are therefore required to promote the dual wetland function of crop production and the mitigation of greenhouse gas emissions especially under future climate change scenarios.
  • Authors:
    • Lawrence, D.
    • Tully, K. L.
    • Scanlon, T. M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 161
  • Year: 2012
  • Summary: The mitigation of nutrient leaching losses is an important ecosystem service, and is easily affected by small-scale management decisions. This study was conducted on eight coffee agroforests in Costa Rica, in order to identify particular mechanisms preventing nutrient leaching losses. First, we examined how nitrogen (N) and phosphorus (P) leaching losses differed between coffee agroforests amended with mineral or organic fertilizers. Monthly N and P concentrations were measured in soil water using tension lysimeters (at 15 and 100 cm) between October 2008 and September 2009, and a water balance model was developed to estimate annual nutrient leaching losses from these agroforests. Second, we examined the effects of human interventions (fertilizer type and quantity), biology (shade trees), and chemistry (soil properties) on nutrient leaching losses. Despite differences in the quantity and form of fertilizer inputs, N and P losses at 100 cm did not differ significantly between organically and conventionally managed agroforests (119 kg N ha -1 yr -1 and 1.5 kg P ha -1 yr -1, respectively). Rather, N losses declined linearly with increasing shade tree biomass, which is determined by farmers. Phosphorus losses, on the other hand, declined with increasing soil iron pools, which are independent of management decisions.
  • Authors:
    • Agus,Fahmuddin
    • Wahyunto
    • Al Dariah
    • Runtunuwu,Eleonora
    • Susanti,Erni
    • Supriatna,Wahyu
  • Source: Journal of Oil Palm Research
  • Volume: 24
  • Issue: August
  • Year: 2012
  • Summary: The peatlands of Indonesia are an increasingly important land resource for the livelihood of the people and for economic development, but they turn rapidly into a carbon source when the peat forests are cleared and drained. Therefore, strategies are needed for the sustainable management of the peatlands and to reduce greenhouse gas emissions. This research was conducted on 464 642 ha of peatland varying in depth between 200 and 680 cm, in the districts of Kubu Raya and Pontianak, in the West Kalimantan province of Indonesia. It was aimed at: (i) evaluating land use changes in the peatland of the two districts and assessing the CO2 emissions these entail; and (ii) recommending options for mitigation of the CO2 emissions. Satellite images in the years 1986, 2002 and 2008 were used for the evaluation of land use changes. This was followed by ground-truthing of recent land cover in 2009. Interviews were conducted with stakeholders to develop emission reduction strategies. The results show that the peatlands were used for various purposes, including the traditional slash-and-burn agriculture for maize, pineapple plantations, intensive vegetable farming, and rubber and oil palm plantations. The peat forest area decreased by 16% from 393 000 ha in 1986 to 329 390 ha in 2008, while shrubland increased by 153% from 9427 ha to 23 814 ha over the same period of time. Oil palm plantations and paddy fields also increased rapidly in expansion. The main sources of emissions were from peat burning, especially for the slash-and-burn farming, peat decomposition due to drainage, and the loss of biomass depending on the land use trajectories. Emission reduction can be achieved through various scenarios. Scenario I, confining future agricultural land development to peatland with peat of <3 m thick, is expected to reduce by 6.8 +/- 2.9% the 2010 to 2035 cumulative CO2 emissions from the 127 million tonnes 'business as usual' (BAU) level. Scenario II, providing fertiliser subsidy to replace the traditional burning technique in addition to Scenario I, is expected to reduce emissions by as much as 11.5 +/- 4.9%. Scenario III, switching future agricultural expansion to mineral soils, is expected to lower the cumulative emissions by as much as 20.5 +/- 8.8%. These scenarios form the basis for sustainable peatland management and for a state of preparedness to reduce emissions from peatland.
  • Authors:
    • Rodrigues, H. O.
    • Lawrence, D.
    • Gaveau, D. A.
    • Trigg, S. N.
    • Asner, G. P.
    • Soares-Filho, B. S.
    • Pittman, A. M.
    • Ratnasari, D.
    • Curran, L. M.
    • Carlson, K. M.
  • Source: Proceedings of the National Academy of Sciences of the United States of America
  • Volume: 109
  • Issue: 19
  • Year: 2012
  • Summary: Industrial agricultural plantations are a rapidly increasing yet largely unmeasured source of tropical land cover change. Here, we evaluate impacts of oil palm plantation development on land cover, carbon flux, and agrarian community lands in West Kalimantan, Indonesian Borneo. With a spatially explicit land change/carbon bookkeeping model, parameterized using high-resolution satellite time series and informed by socioeconomic surveys, we assess previous and project future plantation expansion under five scenarios. Although fire was the primary proximate cause of 1989-2008 deforestation (93%) and net carbonemissions (69%), by 2007-2008, oil palm directly caused 27% of total and 40% of peatland deforestation. Plantation land sources exhibited distinctive temporal dynamics, comprising 81% forests on mineral soils (1994-2001), shifting to 69% peatlands (2008-2011). Plantation leases reveal vast development potential. In 2008, leases spanned similar to 65% of the region, including 62% on peatlands and 59% of community-managed lands, yet < 10% of lease area was planted. Projecting business as usual (BAU), by 2020 similar to 40% of regional and 35% of community lands are cleared for oil palm, generating 26% of net carbon emissions. Intact forest cover declines to 4%, and the proportion of emissions sourced from peatlands increases 38%. Prohibiting intact and logged forest and peatland conversion to oil palm reduces emissions only 4% below BAU, because of continued uncontrolled fire. Protecting logged forests achieves greater carbon emissions reductions (21%) than protecting intact forests alone (9%) and is critical for mitigating carbon emissions. Extensive allocated leases constrain land management options, requiring trade-offs among oil palm production, carbon emissions mitigation, and maintaining community landholdings.
  • 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.