• Authors:
    • Sayre, K. D.
    • Govaerts, B.
    • Deckers, J.
  • Source: Field Crops Research
  • Volume: 94
  • Issue: 1
  • Year: 2005
  • Summary: Subtropical highlands of the world have been densely populated and intensively cropped. Agricultural sustainability problems resulting from soil erosion and fertility decline have arisen throughout this agro-ecological zone. This article considers practices that would sustain higher and stable yields for wheat and maize in such region. A long-term field experiment under rainfed conditions was started at El Batan, Mexico (2240 m a.s.l.; 19.31 degrees N, 98.50 degrees W;fine, mixed, thermic, Cumulic Haplustoll) in 1991. It included treatments varying in: (1) rotation (continuous maize (Zea mays) or wheat (Triticum aestivum) and the rotation of both); (2) tillage (conventional, zero and permanent beds); (3) crop residue management (full, partial or no retention). Small-scale maize and wheat farmers may expect yield improvements through zero tillage, appropriate rotations and retention of sufficient residues (average maize and wheat yield of 5285 and 5591 kg ha(-1)), compared to the common practices of heavy tillage before seeding, monocropping and crop residue removal (average maize and wheat yield of 3570 and 4414 kg ha(-1)). Leaving residue on the field is critical for zero tillage practices. However, it can take some time-roughly 5 years-before the benefits are evident. After that, zero tillage with residue retention resulted in higher and more stable yields than alternative management. Conventional tillage with or without residue incorporation resulted in intermediate yields. Zero tillage without residue drastically reduced yields, except in the case of continuous wheat which, although not high yielding, still performed better than the other treatments with zero tillage and residue removal. Zero tillage treatments with partial residue removal gave yields equivalent to treatments with full residue retention (average maize and wheat yield of 5868 and 5250 kg ha(-1)). There may be scope to remove part of the residues for fodder and still retain adequate amounts to provide the necessary ground cover. This could make the adoption of zero tillage more acceptable for the small-scale, subsistence farmer whose livelihood strategies include livestock as a key component. Raised-bed cultivation systems allow both dramatic reductions in tillage and opportunities to retain crop residues on the soil surface. Permanent bed treatments combined with rotation and residue retention yielded the same as the zero tillage treatments, with the advantage that more varied weeding and fertilizer application practices are possible. It is important small-scale farmers have access to, and are trained in the use of these technologies. (c) 2004 Elsevier B.V. All rights reserved.
  • Authors:
    • Dale, B. E.
    • Kim, S.
  • Source: Biomass and Bioenergy
  • Volume: 26
  • Issue: 4
  • Year: 2004
  • Summary: The global annual potential bioethanol production from the major crops, corn, barley, oat, rice, wheat, sorghum, and sugar cane, is estimated. To avoid conflicts between human food use and industrial use of crops, only the wasted crop, which is defined as crop lost in distribution, is considered as feedstock. Lignocellulosic biomass such as crop residues and sugar cane bagasse are included in feedstock for producing bioethanol as well. There are about 73:9 Tg of dry wasted crops in the world that could potentially produce 49:1 GL year-1 of bioethanol. About 1:5 Pg year-1 of dry lignocellulosic biomass from these seven crops is also available for conversion to bioethanol. Lignocellulosic biomass could produce up to 442 GL year-1 of bioethanol. Thus, the total potential bioethanol production from crop residues and wasted crops is 491 GL year-1, about 16 times higher than the current world ethanol production. The potential bioethanol production could replace 353 GL of gasoline (32% of the global gasoline consumption) when bioethanol is used in E85 fuel for a midsize passenger vehicle. Furthermore, lignin-rich fermentation residue, which is the coproduct of bioethanol made from crop residues and sugar cane bagasse, can potentially generate both 458 TWh of electricity (about 3.6% of world electricity production) and 2:6EJ of steam. Asia is the largest potential producer of bioethanol from crop residues and wasted crops, and could produce up to 291 GL year -1 of bioethanol. Rice straw, wheat straw, and corn stover are the most favorable bioethanol feedstocks in Asia. The next highest potential region is Europe (69:2 GL ofbioethanol), in which most bioethanol comes from wheat straw. Corn stover is the main feedstock in North America, from which about 38:4 GL year -1 of bioethanol can potentially be produced. Globally rice straw can produce 205 GL of bioethanol, which is the largest amount from single biomass feedstock. The next highest potential feedstock is wheat straw, which can produce 104 GL of bioethanol. This paper is intended to give some perspective on the size ofthe bioethanol feedstock resource, globally and by region, and to summarize relevant data that we believe others will 0nd useful, for example, those who are interested in producing biobased products such as lactic acid, rather than ethanol, from crops and wastes. The paper does not attempt to indicate how much, if any, of this waste material could actually be converted to bioethanol.
  • Authors:
    • Sathaye, J. A.
    • Makundi, W. R.
  • Source: Environment, Development and Sustainability
  • Volume: 6
  • Issue: 1-2
  • Year: 2004
  • Summary: This paper summarizes studies of carbon mitigation potential (MP) and costs of forestry options in seven developing countries with a focus on the role of agroforestry. A common methodological approach known as comprehensive mitigation assessment process (COMAP) was used in each study to estimate the potential and costs between 2000 and 2030. The approach requires the projection of baseline and mitigation land-use scenarios derived from the demand for forest products and forestland for other uses such as agriculture and pasture. By using data on estimated carbon sequestration, emission avoidance, costs and benefits, the model enables one to estimate cost effectiveness indicators based on monetary benefit per tC, as well as estimates of total mitigation costs and potential when the activities are implemented at equilibrium level. The results show that about half the MP of 6.9 GtC (an average of 223 MtC per year) between 2000 and 2030 in the seven countries could be achieved at a negative cost, and the other half at costs not exceeding $100 per tC. Negative cost indicates that non-carbon revenue is sufficient to offset direct costs of about half of the options. The agroforestry options analyzed bear a significant proportion of the potential at medium to low cost per tC when compared to other options. The role of agroforestry in these countries varied between 6% and 21% of the MP, though the options are much more cost effective than most due to the low wage or opportunity cost of rural labor. Agroforestry options are attractive due to the large number of people and potential area currently engaged in agriculture, but they pose unique challenges for carbon and cost accounting due to the dispersed nature of agricultural activities in the tropics, as well as specific difficulties arising from requirements for monitoring, verification, leakage assessment and the establishment of credible baselines.
  • Authors:
    • Figueroa-Viramontes, R.
    • Vazquez-Vazquez, C.
    • Salazar-Sosa, E.
    • Lopez-Martinez, J. D.
    • Berumen-Padilla, S.
    • Martinez-Rubin, E.
  • Source: Agrofaz: publicación semestral de investigación científica, ISSN 1665-8892, Vol. 3, Nº. 1, 2003 or Phyton REVISTA INTERNACIONAL DE BOTÁNICA EXPERIMENTAL INTERNATIONAL JOURNAL OF EXPERIMENTAL BOTANY
  • Volume: 2004
  • Year: 2004
  • Summary: Taking into consideration that potential evapotranspiration normally exceeds the growing season rainfall and that a water shortage can occur unless a reserve of soil water is stored before the crop is planted, it can be concluded that the amount of stored soil water at sowing time is a critical factor in the success of dryland cropping systems. The main aim of this investigation was to know if interaction chi 2 test is a valuable tool, when taking into account stored soil (0-60 cm depth) water at sowing time and maize grain yield, in making decision for sowing or not sowing at a given time. Data on the amount of soil water at sowing time and maize grain yield from four experiments carried out during 2001 and 2002 at the Ejido Francisco Villa, Lerdo, Durango, Mexico were used to run the interaction chi 2 tests. For a minimum maize yield of 1000 kg ha -1, the following level of stored soil water was defined as critical: 8.34 cm for cv. 'Blanco Hualauises' and cv. 'H-412'. The interaction chi 2 test is a good tool to determine soil water critical levels at the sowing time of maize to ensure success in the present dryland cropping system.
  • 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:
    • Ruiz-Suárez, L. G.
    • González-Avalos, E.
  • Source: Bioresource Technology
  • Volume: 80
  • Issue: 1
  • Year: 2001
  • Authors:
    • Ortiz-Monasterio, I.
    • Naylor, R.
    • Matson, P. A.
  • Source: Science
  • Volume: 280
  • Issue: 5360
  • Year: 1998
  • Summary: Nitrogen fertilization is a substantial source of nitrogen-containing trace gases that have both regional and global consequences, In the intensive wheat systems of Mexico, typical fertilization practices lead to extremely high fluxes of nitrous oxide (N2O) and nitric oxide (NO). In experiments, lower rates of nitrogen fertilizer, applied later in the crop cycle, reduced the loss of nitrogen without affecting yield and grain quality. Economic analyses projected this alternative practice to save 12 to 17 percent of after-tax profits, A knowledge-intensive approach to fertilizer management can substitute for higher levels of inputs, saving farmers money and reducing environmental costs.
  • Authors:
    • McMahon, M.
    • Rajaram, S.
    • Sayre, K. D.
    • Ortiz-Monasterio, J. I.
  • Source: Crop Science
  • Volume: 37
  • Issue: 3
  • Year: 1997
  • Summary: The adaptation and performance of CIMMYT's bread wheat germplasm (Triticum aesttvum L.) under conditions of low N fertility have been questioned because they were developed under medium-high levels of N fertility. The objectives of this research were to (i) compare the performance of a set of tall vs. semidwarf cultivars developed by CIMMYT that were widely grown by farmers in the Yaqui Valley of Mexico at low and high N fertility, (ii) measure the genetic progress in grain yield and N use efficiency (NUE), and (iii) evaluate the contribution of N uptake efficiency (UPE) and utilization efficiency (UTE) to NUE. Ten wheat cultivars, two tall and eight semidwarf, produced by CIMMYT and released in the Yaqui Valley of Sonora, by the Mexican government from 1950 to 1985 were grown with 0, 75, 150, or 300 kg N ha-1 in a 3-yr field study at Ciudad Obregon, Sonora, Mexico. Genetic gains in both grain yield and NUE during 1950 to 1985 were 1.1, 1.0, 1.2, and 1.9% yr-1 on a relative basis or 32, 43, 59, and 89 kg ha-1 yr-1 on an absolute basis, when provided 0, 75,150, and 300 kg ha-1 N, respectively. Progress in NUE resulted in an improvement of both UPE and UTE. However, the relative importance of these two components was affected by the level of applied N. These results contradict the belief that modern semidwarf cultivars require more N than older cultivars. Instead, they respond more to N, which translates into higher economic rates and higher returns when N fertilizer is available.
  • Authors:
    • Barra, J. D. E.
    • Carretera, A. R. H.
    • Oleschko, K.
  • Source: Soil & Tillage Research
  • Volume: 37
  • Issue: 1
  • Year: 1996
  • Summary: Little is known about the crop influence and the long-term effects of tillage systems on physical and morphological properties of Vertisols in the high plateau of the intertropical zone of Mexico. The purpose of the present study was to evaluate the impact of crop rotation on the development of structure and pedofeatures of Eutric Vertisols of Guanajuato, Mexico. Disturbed and undisturbed samples from the top soil (0-20 cm) of five agroecosystems differing in crop rotation (semipermanent alfalfa, two cereal crops per year, one vegetable and one cereal crop per year, three vegetable crops per year, and dryland maize) were collected. A second no-till soil sample was obtained from a nearby site under secondary vegetation and used as reference soil. Continuous and intensive cultivation lead to a significant reduction in Vertisol organic matter and total nitrogen contents. Tillage and crop rotations affected air-dried aggregate bulk densities, soil microstructure and development of pedofeatures. Calcite crystalline pedofeatures seemed to be more directly affected by the management systems used. Nodules, the most common crystalline pedofeatures in top soil of all cultivated Vertisols, were absent in no-till soils.
  • Authors:
    • De Jong, B. H. G.
    • Montoya-Gómez, G.
    • Nelson, K.
    • Soto-Pinto, L.
    • Taylor, J.
    • Tipper, R.
  • Source: Interciencia
  • Volume: 20
  • Issue: 6
  • Year: 1995
  • Summary: Although forestry and agroforestry are recognized as promising land-use alternatives for reducing the increasing levels of global atmospheric carbon, the viability of carbon sequestration projects at the land-user level has rarely been evaluated. We present the results of a feasibility study to: (1) evaluate the interest of local communities in a carbon sequestration project and how they would organize themselves for the proposed forestry project; (2) identify the carbon sequestration potential of the agroforestry/forestry systems that are both ecologically viable and preferred by local farmers (3) determine the social constraints of and potential for, such projects,- and (4) assess the economic potential of the carbon offsets estimated for such systems. This project was carried out by an interdisciplinary team of scientists and farmers in two ecological regions: the Tojolabal and Tzeltal zones of Chiapas, Mexico. Five systems with high carbon sequestration potential were considered technically and socially viable for each region. Initially, all participants will plant trees on an individual basis in their coffee plantation, fallow, and pasture lands, or in their maize fields. The estimated amount of carbon sequestered ranged from 46 7 to 236 7 tons of carbon per hectare (tC/ha). Net income benefits due to converting fields from maize cultivation to farm forestry ranged from $500-1000/ha depending on the value assigned to the sequestered carbon.1 Forests and farm woodlands that are sustainably managed have substantial economic and carbon sequestration potential. The principal barrier to communal forest management appears to be sociopolitical rather than economic. Because forest management requires long-term investments, good planning is essential and includes community control of projects, selection of appropriate tree species, and management techniques that are specific to the ecological and social conditions of the area. 1 All references to dollars in this report refer to U.S. dollars ($US).