• Authors:
    • Verchot, L.
    • Palm, C.
    • Albrecht, A.
    • Cadisch, G.
    • Mutuo, P.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 71
  • Issue: 1
  • Year: 2005
  • Summary: Losses of carbon (C) stocks in terrestrial ecosystems and increasing concentrations of greenhouse gases in the atmosphere are challenges that scientists and policy makers have been facing in the recent past. Intensified agricultural practices lead to a reduction in ecosystem carbon stocks, mainly due to removal of aboveground biomass as harvest and loss of carbon as CO2 through burning and/or decomposition. Evidence is emerging that agroforestry systems are promising management practices to increase aboveground and soil C stocks and reduce soil degradation, as well as to mitigate greenhouse gas emissions. In the humid tropics, the potential of agroforestry (tree-based) systems to sequester C in vegetation can be over 70 Mg C ha-1, and up to 25 Mg ha-1 in the top 20 cm of soil. In degraded soils of the sub-humid tropics, improved fallow agroforestry practices have been found to increase top soil C stocks up to 1.6 Mg C ha-1 yr-1 above continuous maize cropping. Soil C accretion is linked to the structural development of the soil, in particular to increasing C in water stable aggregates (WSA). A review of agroforestry practices in the humid tropics showed that these systems were able to mitigate N2O and CO2 emissions from soils and increase the CH4 sink strength compared to cropping systems. The increase in N2O and CO2 emissions after addition of legume residues in improved fallow systems in the sub-humid tropics indicates the importance of using lower quality organic inputs and increasing nutrient use efficiency to derive more direct and indirect benefits from the system. In summary, these examples provide evidence of several pathways by which agroforestry systems can increase C sequestration and reduce greenhouse gas emissions.
  • Authors:
    • Jayanthi, C.
    • Shekinah, D. E.
    • Sankaran, N.
  • Source: Journal of Sustainable Agriculture
  • Volume: 25
  • Issue: 3
  • Year: 2005
  • Summary: In a small-scale resource-poor farm, modest increments in productivity are no longer sufficient to justify the investment of scarce resources. Integrated farming systems with multiple enterprises pave the way for realizing increased productivity, profitability and sustainability in small farms of the developing countries. A study conducted at Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India from July 2000 to March 2002 to optimize enterprise combination, increase employment and bring about maximum bioresource utilization and residue recycling for a 1-ha farm of the dryland tract of the western zone of Tamil Nadu compared four farming system combinations: FS 2 (crop+pigeon+goat+agroforestry+farm pond), FS 3 (crop+pigeon+buffalo+agroforestry+farm pond), and FS 4 (crop+pigeon+goat+buffalo+agroforestry+farm pond) with FS 1 (sorghum only) as the reference system. The results indicated the following: crop (0.80 ha) fertilized with buffalo manure produced on the farm, with pigeon (10 pairs on 0.01 ha), goat (5:1 female:male on 0.02 ha), buffalo (2 milking buffaloes+1 calf on 0.03 ha), agroforestry (0.10 ha) and farm pond (0.04 ha) was the profitable system enterprise that generated higher employment year-round. This system also facilitated the maximum recycling of resources and residues generated on the farm among the enterprises. The output and the waste of one enterprise served as input to another. The nutritive value of the system in terms of carbohydrate, protein and fat was also highest with this enterprise combination. Thus, FS 4 seems to be the best enterprise combination as revealed by the physical indicators. However, since the purchase and maintenance of buffalo enterprise involves higher costs, for farmers who have limited cash for investment, linkage of crop (0.80 ha) with pigeon (10 pairs on 0.01 ha), goat (5:1 female:male on 0.05 ha), agroforestry (0.10 ha) and farm pond (0.04 ha) is suggested as the alternative farming system for sustainability instead of conventional cropping alone.
  • Authors:
    • Chattopadhyay, N.
    • Das, H. P.
  • Source: Advances in Indian entomology: productivity and health (a silver jubilee supplement)
  • Volume: 1
  • Issue: 3
  • Year: 2005
  • Summary: Every year crops (such as rice, cotton, pigeon pea, sorghum, soyabean, groundnut, sugarcane and vegetables) are being damaged by pests and diseases. Due to lack of proper operational forecasting system for the incidences of pests and diseases, it becomes difficult to adopt efficient plant protection measures at the right time. It has been established with fair degree of accuracy that climate/weather plays major role in the incidences of pests and diseases. Thus, there is a tremendous scope of utilizing meteorological parameters for the advance information of the occurrences of the pests and diseases and ultimately scheduling of prophylactive measures can be taken scientifically and judiciously. Quite a number of studies in this regards have been made in the Agricultural Meteorology Division, India Meteorological Department (Pune, Maharashtra, India). In the present paper, a comprehensive review of the work done in this division on the impact of weather on pests and diseases of crops is presented. This information will probably help the agricultural community of the country to save the crops from the infestation of pest and disease incidences.
  • Authors:
    • Jones, P. G.
    • Atieno, F.
    • Kruska, R. L.
    • McCrabb, G.
    • Thornton, P. K.
    • Reid, R. S.
  • Source: Environment, Development and Sustainability
  • Volume: 6
  • Issue: 1-2
  • Year: 2004
  • Summary: Climate change science has been discussed and synthesized by the world's best minds at unprecedented scales. Now that the Kyoto Protocol may become a reality, it is time to be realistic about the likelihood of success of mitigation activities. Pastoral lands in the tropics hold tremendous sequestration potential but also strong challenges to potential mitigation efforts. Here we present new analyses of the global distribution of pastoral systems in the tropics and the changes they will likely undergo in the next 50 years. We then briefly summarize current mitigation options for these lands. We then conclude by attempting a pragmatic look at the realities of mitigation. Mitigation activities have the greatest chance of success if they build on traditional pastoral institutions and knowledge (excellent communication, strong understanding of ecosystem goods and services) and provide pastoral people with food security benefits at the same time.
  • Authors:
    • Moreira, A.
    • Martins, G.
    • Mccann, J.
    • German, L.
    • Kern, D.
    • Lehmann, J.
  • Source: Amazonian Dark Earths
  • Volume: Part 2
  • Year: 2004
  • Authors:
    • Thomas, R. J.
    • Fisher, M. J.
  • Source: Environment, Development and Sustainability
  • Volume: 6
  • Issue: 1-2
  • Year: 2004
  • Summary: Three of the nine physiographic regions that comprise the 8.2 million km2 (Mkm2) of the central lowlands of tropical South America have undergone substantial conversion from the native vegetation in the last 30 years, a good deal of it to introduced pastures. The converted lands were either formerly treeless grasslands of the Brazilian Shield and the Orinoco Basin, or semi-evergreen seasonal forest mainly in the east and southwest of the Amazon Basin in Brazil. There are about 0.44Mkm2 of introduced Brachiaria pastures in the former grasslands and we estimate that there are 0.096Mkm2 of introduced pastures in the Amazon Basin, mostly Brachiaria species. Based on extensive descriptions of the land systems of the central lowlands by Cochrane et al. (1985) we extrapolated data of carbon (C) accumulation in the soil under introduced pastures on the eastern plains of Colombia (about 3 t Cha-1 yr-1), which are treeless grasslands of the Orinoco Basin, to estimate the probable change in C stocks as a result of conversion to pasture elsewhere. Losses of above-ground C on conversion of the former grasslands is negligible, while in contrast the forests probably lose about 115 t C for each ha converted. We estimated the mean time since conversion started and allowed for the degradation of the pastures that commonly occurs. We concluded that introduced pastures on the former grasslands have been a net sink for about 900 million t (Mt) C, while conversion of the forest has been a net source of about 980 Mt C, leading to a net source of about 80 Mt C for the central lowlands as a whole. We identify a number of issues and possible methodologies that would improve precision of the estimates of the changes in C stocks on conversion of native vegetation to pasture.
  • Authors:
    • Shively, G. E.
    • Zelek, C. A.
  • Source: Land Economics
  • Volume: 79
  • Issue: 3
  • Year: 2003
  • Summary: We present a method for measuring the opportunity cost of sequestering carbon on tropical farms. We derive the rates of carbon sequestration for timber and agroforestry systems and compute incentive compatible compensating payment schedules for farmers who sequester carbon. The method is applied to data for an agricultural watershed in the Philippines. Area- and land quality-adjusted total costs are estimated. The present value of the opportunity cost of carbon storage via land modification falls between $3.30 and $62.50 per ton. Carbon storage through agroforestry is found to be less costly than via a pure tree-based system.
  • Authors:
    • Glaser, B.
    • Zech, W.
    • Nehls, T.
    • Steiner, C.
    • Pereira da Silva, J.
    • Lehmann, J.
  • Source: Plant and Soil
  • Volume: 249
  • Issue: 2
  • Year: 2003
  • Authors:
    • Yang, H.
    • Walters, D. T.
    • Dobermann, A.
    • Cassman, K. G.
  • Source: Annual Review of Environment and Resources
  • Volume: 28
  • Issue: 1
  • Year: 2003
  • Summary: Agriculture is a resource-intensive enterprise. The manner in which food production systems utilize resources has a large influence on environmental quality. To evaluate prospects for conserving natural resources while meeting increased demand for cereals, we interpret recent trends and future trajectories in crop yields, land and nitrogen fertilizer use, carbon sequestration, and greenhouse gas emissions to identify key issues and challenges. Based on this assessment, we conclude that avoiding expansion of cultivation into natural ecosystems, increased nitrogen use efficiency, and improved soil quality are pivotal components of a sustainable agriculture that meets human needs and protects natural resources. To achieve this outcome will depend on raising the yield potential and closing existing yield gaps of the major cereal crops to avoid yield stagnation in some of the world's most productive systems. Recent trends suggest, however, that increasing crop yield potential is a formidable scientific challenge that has proven to be an elusive goal.
  • Authors:
    • Thornton, P. K.
    • Jones, P. G.
  • Source: Conservation Ecology
  • Volume: 5
  • Issue: 2
  • Year: 2003
  • Summary: Making decisions in natural resource management involves an understanding of the risk and uncertainty of the outcomes, such as crop failure or cattle starvation, and of the normal spread of the expected production. Hedging against poor outcomes often means lack of investment and slow adoption of new methods. At the household level, production instability can have serious effects on income and food security. At the national level, it can have social and economic impacts that may affect all sectors of society. Crop models such as CERES-Maize are excellent tools for assessing weather-related production variability. WATBAL is a water balance model that can provide robust estimates of the potential growing days for a pasture. These models require large quantities of daily weather data that are rarely available. MarkSim is an application for generating synthetic daily weather files by estimating the third-order Markov model parameters from interpolated climate surfaces. The models can then be run for each distinct point on the map. This paper examines the growth of maize and pasture in dryland agriculture in southern Africa (includes the southern part of Tanzania, Malawi, much of Mozambique, and all of Zimbabwe, and extends west from the Indian Ocean to include Zambia, the southeastern part of the Democratic Republic of Congo and small portions of Angola). Weather simulators produce independent estimates for each point on the map; however, we know that a spatial coherence of weather exists. We investigated a method of incorporating spatial coherence into MarkSim and show that it increases the variance of production. This means that all of the farmers in a coherent area share poor yields, with important consequences for food security, markets, transport, and shared grazing lands. The long-term aspects of risk are associated with global climate change. We used the results of a global circulation model to extrapolate to the year 2055. We found that low maize yields would become more likely in the marginal areas, whereas they may actually increase in some areas. The same trend was found with pasture growth. We outline areas where further work is required before these tools and methods can address natural resource management problems in a comprehensive manner at local community and policy levels.