31. Effects of tillage, irrigation and fertilization on infestation of corn ears by lepidopteran larvae and fungi in northeastern Mexico.

• Authors:
  • Rodriguez-del-Bosque, L.
  • Salinas-Garcia, J.
• Source: Journal of Entomological Science
• Volume: 43
• Issue: 2
• Year: 2008
• Summary: The effects of tillage, irrigation (10 cm each at 10- to 14-leaf stage, and silking and milk stages, and no supplemental irrigation) and fertilizer (NPK at 0:0:0 or 140:40:0 kg/ha) treatments on the incidence of lepidopteran insects and fungi infesting maize (cv. Pioneer 3025W) were studied in Tamaulipas, Mexico, during 2005-07. The tillage treatments consisted of mouldboard ploughing (discing stalks after harvesting, followed by mouldboard ploughing, discing and row establishment), subsoil-bedding (shredding stalks after harvesting, followed by subsoiling on row centres and establishment of beds), shred-bedding (shredding stalks after harvesting, followed by bedding on old rows), and no-tillage (shredding stalks after harvesting, and spraying 0.6 kg glyphosate and 0.72 kg 2,4-D/ha twice for weed control). Mouldboard ploughing represented conventional tillage, whereas subsoil-bedding and shred-bedding were reduced tillage systems. The lepidopteran species recorded were Helicoverpa zea (86%) and Spodoptera frugiperda (14%). The incidence of these pests was highest in 2006 (91.5%) and lowest in 2007 (49.3%). The most common fungi were Fusarium spp., the highest incidence of which was registered in 2005 (24.4%). The incidence of Aspergillus flavus and Ustilago maydis [ U. zeae] was less than 4.0% regardless of the year. The incidence of lepidopterans significantly varied between the irrigation levels only (greater pest population under dryland farming). Fusarium spp. and A. flavus occurred more frequently under no-tillage compared with other tillage practices. The incidence of Fusarium spp. was higher in irrigated than in dryland maize.

32. Impact of tillage and arbuscular mycorrhiza inoculation on charcoal rot and yield of maize under semiarid conditions.; Impacto de labranza e inoculacion micorrizica arbuscular sobre la pudricion carbonosa y rendimiento de maiz en condiciones semiaridas.

• Authors:
  • Diaz Franco, A.
  • Salinas Garcia, J. R.
  • Garza Cano, I.
  • Mayek Perez, N.
• Source: Revista Fitotecnia Mexicana
• Volume: 31
• Issue: 3
• Year: 2008
• Summary: Conservation tillage promotes agricultural soil sustainability and the inoculation of arbuscular mycorrhiza fungi (AMF) enhances crop growth and yields. In this study, single and combined effects of tillage systems and inoculation of AMF on charcoal rot ( Macrophomina phaseolina) incidence and severity, and grain yield in maize ( Zea mays L.) were determined. The study was conducted in semi-arid dryland conditions. Three factors with different levels were tested in maize hybrid 'Pioneer 3025W': four tillage systems (moldboard or conventional tillage, subsoil-bedding, shred-bedding and no-tillage); two fertilization levels (inoculated seeds with AMF Glomus intraradices, and fertilization rate of 60N-40P-00K); and three years of evaluation (2003 to 2005). Chlorophyll leaf index (CI), incidence (IM) and severity (SM) of M. phaseolina, arbuscular mycorrhizal colonization (AMC), and grain yield (GY) were determined. No tillage showed the lowest charcoal rot (IM and SM), but also the lowest GY. Tillage systems did not affect AMC of maize. Inoculation was similar to chemical fertilization in CI, IM, SM and GY, although with increase of AMC on mycorrhization treatment. The highest values CI, lesser IM and SM, and highest GY were found in 2004 due to the highest rain fall (460 mm) compared to 2003 (230 mm) and 2005 (125 mm). Results indicate that conservation tillage is a strategy to reduce charcoal in maize crop, although associated with grain yield losses, respect to conventional tillage.

33. GM crops: global socio-economic and environmental impacts 1996-2006

• Authors:
  • Barfoot, P.
  • Brookes, G.
• Year: 2008

34. Evaluation of five plant species as cover crops in the high valleys of Mexico.; Evaluacion de cinco especies vegetales como cultivos de cobertura en valles altos de Mexico.

• Authors:
  • Castillo Gonzalez, F.
  • Perez Olvera, M. A.
  • Navarro Garza, H.
• Source: Revista Fitotecnia Mexicana
• Volume: 30
• Issue: 2
• Year: 2007
• Summary: In this study we compared the plant coverage ability and main agronomic characteristics of five plant species in Nonoalco (2250 masl) and Ixayoc (2500 masl) in north eastern State of Mexico. The populations were: Scarlet runner bean ( Phaseolus coccineus), two faba bean varieties ( Vicia faba, var 'Purepecha' and 'V-35'), common vetch ( Vicia sativa), and oat ( Avena sativa var 'Saia'), in an experimental design in random blocks with three replications, in 6*4 m experimental plots. The scarlet runner and faba beans were planted in rows, while the vetch and oat were thrown sowed. The main variables evaluated were: percentage of area coverage and plant height, on four dates; biomass production at 70 d and at harvest, and grain yield. The results showed differences among populations in ground coverage and agronomic characteristics. Oat and vetch had the best ground cover in both sites. Oat showed the highest growth in both sites, and vetch had the second best behavior. The 'Purepecha' faba bean showed the lowest growth in both sites. The highest production of biomass for all populations in both periods, were obtained in Nonoalco because of its physical-chemical soil characteristics.

35. Residue removal and climatic effects on soil carbon content of no-till soils

• Authors:
  • Torbert, H. A.
  • Scopel, E.
  • Velazquez-Garcia, I.
  • Potter, K. N.
• Source: Journal of Soil and Water Conservation
• Volume: 62
• Issue: 2
• Year: 2007
• Summary: While no-till management practices usually result in increased soil organic carbon (SOC) contents, the effect of residue removal with no-till is not well understood, especially in warmer climates. A multi-year study was conducted at six locations having a wide range of climatic conditions in central Mexico to determine the effect of varying rates of residue removal with no-till oil SOC. Mean annual temperatures ranged from 16 degrees C to 27 degrees C (61 degrees F to 81 degrees F). Mean annual rainfall ranged from 618 to 1099 min yr(-1) (24 to 43 in yr(-1)). Treatments consisted of annual moldboard plowing under residue and no-till with 100%, 66%, 33%, and no corn (Zea mays L.) residue retained oil the no-till surface. At five of the six locations, no-till with all surface residues removed maintained SOC levels above that of moldboard plowing which incorporated all residues. Retaining 100% of the crop residues with no-till always increased or maintained the SOC content. SOC increased in cooler climates, but as mean annual temperature increased, more retained crop residues were needed to increase the SOC. In tropical (mean annual temperature > 20 degrees C) conditions, 100% corn residue retention with no-till only maintained SOC levels. Mean annual temperature ad a greater impact oil SOC than did annual rainfall. It appears that, in warmer climates, residue in excess of that needed for erosion control may be used for animal fodder or energy production. At the higher temperatures, most of the residue will decompose if left oil the soil surface Without improving soil carbon contents.

36. The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle

• Authors:
  • Rose, A. Z.
  • Marland, G.
  • Houghton, R. A.
  • Fairman, D. M.
  • Zimmerman, G. P.
  • Dilling, L.
  • Wilbanks, T. J.
  • King, A. W.
• Year: 2007
• Summary: North America is currently a net source of carbon dioxide to the atmosphere, contributing to the global buildup of greenhouse gases in the atmosphere and associated changes in the earth's climate. In 2003, North America emitted nearly two billion metric tons of carbon to the atmosphere as carbon dioxide. North America's fossil fuel emissions in 2003 (1856 million metric tons of carbon ±10% with 95% certainty) were 27% of global emissions. Approximately 85% of those emissions were from the United States, 9% from Canada and 6% from Mexico. The conversion of fossil fuels to energy (primarily electricity) is the single largest contributor, accounting for approximately 42% of North American fossil emissions in 2003. Transportation is the second largest, accounting for 31% of total emissions. There are also globally important carbon sinks in North America. In 2003, growing vegetation in North America removed approximately 530 million tons of carbon per year (± 50%) from the atmosphere and stored it as plant material and soil organic matter. This land sink is equivalent to approximately 30% of the fossil fuel emissions from North America. The imbalance between the fossil fuel source and the sink on land is a net release to the atmosphere of 1335 million metric tons of carbon per year (± 25%). Approximately 50% of North America's terrestrial sink is due to the regrowth of forests in the United States on former agricultural land that was last cultivated decades ago, and on timber land recovering from harvest. Other sinks are relatively small and not well quantified with uncertainties of 100% or more. The future of the North American terrestrial sink is also highly uncertain. The contribution of forest regrowth is expected to decline as the maturing forests grow more slowly and take up less carbon dioxide from the atmosphere. But, this expectation is surrounded by uncertainty because how regrowing forests and other sinks will respond to changes in climate and carbon dioxide concentration in the atmosphere is highly uncertain. The large difference between current sources and sinks and the expectation that the difference could become larger if the growth of fossil fuel emissions continues and land sinks decline suggest that addressing imbalances in the North American carbon budget will likely require actions focused on reducing fossil fuel emissions. Options to enhance sinks (growing forests or sequestering carbon in agricultural soils) can contribute, but enhancing sinks alone is likely insufficient to deal with either the current or future imbalance. Options to reduce emissions include efficiency improvement, fuel switching, and technologies such as carbon capture and geological storage. Implementing these options will likely require both voluntary and policy-driven mechanisms at local, regional, national, and international levels. Meeting the demand for information by decision makers will likely require new modes of research characterized by close collaboration between scientists and carbon management stakeholders.

37. The potential of fruit trees to enhance converted habitats for migrating birds in southern Mexico

• Authors:
  • Foster, Mercedes S.
• Source: Bird Conservation International
• Volume: 17
• Issue: 1
• Year: 2007
• Summary: Migration routes used by Nearctic migrant birds can cover great distances; they also differ among species, within species, and between years and seasons. As a result, migration routes for an entire migratory avifauna can encompass broad geographic areas, making it impossible to protect continuous stretches of habitat sufficient to connect the wintering and breeding grounds for most species. Consequently, ways to enhance habitats converted for human use (i.e. for pasture, crop cultivation, human settlement) as stopover sites for migrants are especially important. Shelterbelts around pastures and fields, if planted with species targeted to support migrant (and resident) bird species that naturally occupy mature forest habitats and that are at least partially frugivorous, could be a powerful enhancement tool for such species, if the birds will enter the converted areas to feed. I tested this approach for Nearctic migrant birds during the spring migration through an area in Chiapas, Mexico. Mature forest tree species whose fruits are eaten by birds were surveyed. Based on life form, crop size and fruit characteristics, I selected three tree species for study: Cymbopetalum mayanum (Annonaceae), Bursera simaruba (Burseraceae) and Trophis racemosa (Moraceae). I compared the use of fruits of these species by migrants and residents in forest with their use of the fruits of isolated individuals of the same species in pasture and cropland. All three plant species Were useful for enhancing converted habitats for forest-occupying spring migrants, although species differed in the degree to which they entered disturbed areas to feed on the fruits. These tree species could probably enhance habitats for migrants at sites throughout the natural geographic ranges of the plants; in other geographic areas for other target bird groups, other tree Species might be more appropriate.

38. Agricultural intensification: will land spared from farming be land spared for nature?

• Authors:
  • Vitousek, P. M.
  • Matson, P. A.
• Source: Conservation Biology
• Volume: 20
• Issue: 3
• Year: 2006
• Summary: How can intensive agricultural systems be designed so that they have fewer and smaller impacts on surrounding ecosystems? This is not a new challenge, but its importance to conservation—particularly in developing regions—has become apparent in recent years. This challenge is a major part of the ongoing effort to provide for the needs of a growing human population and at the same time sustain the life-support systems of the planet.

39. The carbon balance of North American wetlands

• Authors:
  • Trettin, C. C.
  • Bliss, N. B.
  • Keller, J. K.
  • Megonigal, J. P.
  • Bridgham, S. D.
• Source: Wetlands
• Volume: 26
• Issue: 4
• Year: 2006
• Summary: We examine the carbon balance of North American wetlands by reviewing and synthesizing the published literature and soil databases. North American wetlands contain about 220 Pg C, most of which is in peat. They are a small to moderate carbon sink of about 49 Tg C yr(-1), although the uncertainty around this estimate is greater than 100%, with the largest unknown being the role of carbon sequestration by sedimentation in freshwater mineral-soil wetlands. We estimate that North American wetlands emit 9 Tg methane (CH4) yr(-1); however, the uncertainty of this estimate is also greater than 100%. With the exception of estuarine wetlands, CH4 emissions from wetlands may largely offset any positive benefits of carbon sequestration in soils and plants in terms of climate forcing. Historically, the destruction of wetlands through land-use changes has had the largest effects on the carbon fluxes and consequent radiative forcing of North American wetlands. The primary effects have been a reduction in their ability to sequester carbon (a small to moderate increase in radiative forcing), oxidation of their soil carbon reserves upon drainage (a small increase in radiative forcing), and reduction in CH4 emissions (a small to large decrease in radiative forcing). It is uncertain how global changes will affect the carbon pools and fluxes of North American wetlands. We will not be able to predict accurately the role of wetlands as potential positive or negative feedbacks to anthropogenic global change without knowing the integrative effects of changes in temperature, precipitation, atmospheric carbon dioxide concentrations, and atmospheric deposition of nitrogen and sulfur on the carbon balance of North American wetlands.

40. Carbon dynamics and sequestration in an irrigated Vertisol in Central Mexico

• Authors:
  • Castellanos, J. Z.
  • Buenger, E. D.
  • Follett, R. F.
• Source: Soil & Tillage Research
• Volume: 83
• Issue: 1
• Year: 2005
• Summary: Conservation tillage could enhance soil organic carbon (SOC) sequestration, but is rarely used in cropping systems in Mexico, especially under irrigation. A study was conducted on a clayey, smectitic, isothermic Udic Pellustert to evaluate the use of traditional-deep and no-tillage systems on SOC dynamics for wheat (Triticum aestivum L.)-corn (Zea mays L.) and wheat-bean (Phaseolus vulgaris L.) cropping systems. Experimental design was a randomized block of five tillage/crop-rotation (two crops per year) systems with four replications: (WC-CTb) wheat-corn, burning the residues of both crops, plowing and disking twice (WC-CT) wheat-corn under conventional tillage (plowing and disking twice to incorporate crop residues following the harvest of each crop), (WC-NT) wheat-corn under no-till, (WB-CT) wheat-bean under conventional tillage, and (WB-NT) wheat-bean under no-till. Each crop in the sequence received one of three fertilizer-N rates broadcast as urea: (a) 0, 150, and 300 kg N ha(-1) for corn; (b) 0, 40, and 80 kg N ha(-1) for bean; and (c) 0, 125, and 250 kg N ha(-1) for wheat. The baseline year was 1994, and relative changes were measured from 1994 to 1999 for grain yield and residue production, crop residue C and delta(13)C, SOC, soil C/N ratio, and change in soil delta(13)C. Interaction of cropping system x fertilizer-N rate was highly important to grain yield and crop residue production and amount of crop-residue C produced. High N rates increased SOC sequestration and decreased soil C/N ratios. In WC systems, more negative delta(13)C was associated with higher N rates, indicating increased contribution of wheat (a C(3) plant) residue C relative to corn (a C(4) plant). In WB, N-rate and tillage had no effect on SOC sequestration. Highest rate of SOC sequestration was under WC-NT and when increases in SOC from 1994 to 1999 were annualized was 1.0 and 1.9 Mg SOC yr(-1) in the 0-15- and 15-30-cm depths, respectively. Corresponding SOC in 0-15- and 15-30-cm depths in the WC-CT treatment was 0.2 and 0.6 Mg yr(-1) and amounts in all other treatments were equal or lower than those observed for WC-CT. There was a significant correlation between aboveground crop-residue C produced and amount of SOC sequestered. Results from this study indicate no-till on N-fertilized WC systems can potentially increase SOC sequestration on large areas of irrigated Vertisols in Central Mexico while maintaining high crop yields.