• Authors:
    • Yamaguchi, J.
  • Source: JIRCAS International Symposium Series
  • Issue: 13
  • Year: 2006
  • Summary: Involvement in environment issues and population carrying capacity was analysed based on three typical agricultural systems: slash and burn semi-sedentary agriculture, recycling agriculture in which organic materials are re-used, and non-cyclic agriculture in which nutrient supply depends chiefly on chemical fertilizers. Our analysis showed that, due to its high productivity, non-cyclic agriculture is obligatory to support an ever-growing population and to offset the resultant continuous loss of arable land per person. Fertilizers to be applied should be quantified to exactly meet the balance between plant requirements and natural supply. Excess application of fertilizers should always be avoided. Degradation of soils in the tropics is caused mainly by water and wind erosion, and to a lesser extent from nutrient disturbance (mainly from shortages). The environmental protective effects of permanent crops are shown using two examples. One is in Erimo, Hokkaido (Japan), where fishermen have revived their local fisheries by reforesting the coastline, and the other in Tanzania where indigenous people thrive on the permanent culture of bananas. In the tropics, the use of vegetation as soil cover confers advantages in highly fragile areas, if only because of protection from erosion. The introduction of permanent crops is an alternative to establishing co-existence between agriculture and the environment.
  • Authors:
    • Norby, R. J.
    • Matamala, R.
    • Miller, R. M.
    • Jastrow, J. D.
    • Boutton, T. W.
    • Rice, C. W.
    • Owensby, C. E.
  • Source: Global Change Biology
  • Volume: 11
  • Issue: 12
  • Year: 2005
  • Summary: The general lack of significant changes in mineral soil C stocks during CO2-enrichment experiments has cast doubt on predictions that increased soil C can partially offset rising atmospheric CO2 concentrations. Here, we show, through meta-analysis techniques, that these experiments collectively exhibited a 5.6% increase in soil C over 2-9 years, at a median rate of 19 g C m(-2) yr(-1). We also measured C accrual in deciduous forest and grassland soils, at rates exceeding 40 g C m(-2) yr(-1) for 5-8 years, because both systems responded to CO2 enrichment with large increases in root production. Even though native C stocks were relatively large, over half of the accrued C at both sites was incorporated into microaggregates, which protect C and increase its longevity. Our data, in combination with the meta-analysis, demonstrate the potential for mineral soils in diverse temperate ecosystems to store additional C in response to CO2 enrichment.
  • Authors:
    • Arshad, M. A.
    • Franzluebbers, A. J.
    • Azooz, R. H.
  • Source: Soil & Tillage Research
  • Volume: 77
  • Issue: 1
  • Year: 2004
  • Summary: Conservation tillage has become a major soil management strategy to reduce soil erosion and improve soil quality, yet the impacts of crop rotation on soil responses to conservation tillage remain poorly described. We investigated the effects of (i) perennial grass cover versus annual cropping and (ii) type of break crop in a wheat (Triticum aestivum L.)-based crop rotation system on surface-soil (0-10 cm) structural and organic matter properties towards the end of a decade of continuous management on an Albic Luvisol in the cold, semiarid region of northwestern Canada. Soil aggregation was at state to resist water erosion more under perennial grass (i.e. bromegrass (Bromus inermis Leyss.) and red fescue (Festuca rubra L.)) than under annual cropping systems (mean-weight diameter of 2.1 and 1.6 mm under perennial and annual systems, respectively). Soil organic C was higher (44 g C kg-1 soil versus 38 g C kg-1 soil), but total soil N was lower (3.5 g N kg-1 soil versus 3.9 g N kg-1 soil) under perennial compared with annual cropping systems. There were few significant differences in soil-structural properties among the various annual cropping systems. The largest effect was greater light-fraction C and N under continuous wheat (4.0 g C kg-1 soil and 0.27 g N kg-1 soil) compared with other rotations, especially wheat-wheat-fallow (2.4 g C kg-1 soil and 0.16 g N kg-1 soil), as a result of higher residue inputs. Relationships between mean-weight diameter of water-stable aggregates and biochemical properties were strongest for soil microbial biomass C and soil organic C. Perennial grass cover exhibited greater potential to preserve soil-structural properties than no-tillage annual cropping.
  • Authors:
    • Rice, C. W.
    • Kocylgit, R.
  • Source: Turkish Journal of Agriculture & Forestry
  • Volume: 28
  • Issue: 3
  • Year: 2004
  • Summary: Soil carbon (C) dynamics is an important aspect of the global C cycle. Soils can be a sink or source for atmospheric CO2 depending upon management. Tallgrass prairie and wheat (Triticum aestivum L.) are 2 dominant ecosystems in the Great Plains. This study determined the distribution of C in these 2 ecosystems. Soil C pools, plant root biomass, and aboveground plant biomass were determined at a wheat (winter wheat) and a tallgrass prairie site in northern Oklahoma from 1998 through 2001. The objectives of this study were to determine C storage and changes in soil organic matter in tallgrass prairie and wheat ecosystems under similar environmental conditions and soil characteristics. Soil C was assessed by measuring soil C pools (active, slow and recalcitrant). Mineralizable C and N (Co and No) were determined by long-term laboratory incubation, 314 days at 35 degreeC. Soil C and N content was 2 times greater in the prairie than under wheat. The greater level of Co and No occurred in prairie. Wheat had proportionally greater mineralizable C and N than did prairie, but microbial biomass was the opposite, being greater in prairie. Wheat had more dynamic C pools with a faster turnover rate than did prairie. The more dynamic C pools with a faster turnover rate in wheat was the result of the greater disturbance effects of intensive tillage practices on soil structure.
  • Authors:
    • Chapman, D. F.
    • White, R. E.
    • Chen, D.
    • Eckard, R. J.
  • Source: Australian Journal of Agricultural Research
  • Volume: 54
  • Year: 2003
  • Authors:
    • Intergovernmental Panel on Climate Change
  • Year: 2003
  • Summary: This report on Good Practice Guidance for Land Use, Land-Use Change and Forestry (GPG-LULUCF) is the response to the invitation by the United Nations Framework Convention on Climate Change (UNFCCC)1 to the Intergovernmental Panel on Climate Change (IPCC)2 to develop good practice guidance for land use, land-use change and forestry (LULUCF). GPG-LULUCF provides supplementary methods and good practice guidance for estimating, measuring, monitoring and reporting on carbon stock changes and greenhouse gas emissions from LULUCF activities under Article 3, paragraphs 3 and 4, and Articles 6 and 12 of the Kyoto Protocol.
  • Authors:
    • Dennis, P. F.
    • Fukada, T.
    • Mühlherr ,I. H.
    • Bateman, A. S.
    • Hiscock, K. M.
  • Source: Environmental Science & Technology
  • Volume: 37
  • Issue: 16
  • Year: 2003
  • Summary: Diffuse pollution of groundwater by agriculture has caused elevated concentrations of nitrate (NO3 ) and nitrous oxide (N2O) in regional aquifers. N2O is an important "greenhouse" gas, yet there are few estimates of indirect emissions of N2O from regional aquifers. In this study, high concentrations of N2O (mean 602 nM) were measured in the unconfined Chalk aquifer of eastern England, in an area of intensive agriculture. In contrast, pristine ground waters from upland regions of England and Scotland, with predominantly natural vegetation cover, were found to have much lower concentrations of N2O (mean 27 nM). A positive relationship between N2O and NO3 concentrations and [sigma]18 O-NO3 values of between 3.36 and 16.00‰ suggest that nitrification is the principal source of N2O. A calculated emission factor (EF5-g) of 0.0019 for indirect losses ofN2O from Chalk groundwater is an order of magnitude lower than the value of 0.015 currently used in the Intergovernmental Panel on Climate Change (IPCC) methodology for assessing agricultural emissions. A flux of N2O from the major UK aquifers of 0.04 kg N2O Nha-1 a-1 has been calculated using two approaches and suggests that indirect losses of N2O from regional aquifers are much less significant ( 1%) than direct emissions from agricultural soils.
  • Authors:
    • Cole, C.
    • Westfall, D.
    • Peterson, G.
    • Wood, C.
    • Willis, W.
  • Source: Agronomy Journal
  • Volume: 83
  • Issue: 3
  • Year: 1991
  • Summary: Soil-crop management affects the soil-N balance and, thus, has a direct bearing on soil productivity. This study determined the effects of cropping intensity (crops/time) under no-till and grassland establishment on aboveground biomass production and the system-N balance after 4 yr (1985-1989). The effects were examined across toposequences in the West Central Great Plains that had been tilled and frequently fallowed for > 50 yr. Production systems included wheat (Triticum aestivum L.)-fallow (WF), wheat-corn (Zea mays L.) or sorghum (Sorghum vulgare L.)-millet (Panicum miliaceum L.)-fallow (WCMF), and perennial grass (CG). Intense agronomic systems (WCMF) had greater aboveground production, greater N uptake, and greater percent plant residue retention than WF. Continuous grass systems had less aboveground production and N uptake but greater percent plant residue retention than agronomic systems. Soil-profile NO3-N was lower under WCMF systems than WF systems, but organic N showed the opposite trend implying that more intense systems are at less risk for NO3-N leaching, and have greater potential for replenishment of soil-organic N via enhanced immobilization. Aboveground biomass production and plant residue production increased downslope, but slope position had little effect on plant-N uptake, plant residue retention, or soil-N dynamics. Imposing no-till and perennial grassland systems created a N-balance disequilibrium, but more time will be required to ascertain the trajectory of N loss or gain due to establishment of no-till or grassland management on these soils.