• Authors:
    • Zhang, C.
    • Lu, C. Q.
    • Ren, W.
    • Liu, M. L.
    • Chen, G. S.
    • Tian, H. Q.
    • Xu, X. F.
  • Source: Biogeosciences
  • Volume: 9
  • Issue: 4
  • Year: 2012
  • Summary: Nitrous oxide (N2O) is a potent greenhouse gas which also contributes to the depletion of stratospheric ozone (O-3). However, the magnitude and underlying mechanisms for the spatiotemporal variations in the terrestrial sources of N2O are still far from certain. Using a process-based ecosystem model (DLEM - the Dynamic Land Ecosystem Model) driven by multiple global change factors, including climate variability, nitrogen (N) deposition, rising atmospheric carbon dioxide (CO2), tropospheric O-3 pollution, N fertilizer application, and land conversion, this study examined the spatial and temporal variations in terrestrial N2O flux over North America and further attributed these variations to various driving factors. From 1979 to 2010, the North America cumulatively emitted 53.9 +/- 0.9 Tg N2O-N (1 Tg = 10(12) g), of which global change factors contributed 2.4 +/- 0.9 Tg N2O-N, and baseline emission contributed 51.5 +/- 0.6 Tg N2O-N. Climate variability, N deposition, O-3 pollution, N fertilizer application, and land conversion increased N2O emission while the elevated atmospheric CO2 posed opposite effect at continental level; the interactive effect among multiple factors enhanced N2O emission over the past 32 yr. N input, including N fertilizer application in cropland and N deposition, and multi-factor interaction dominated the increases in N2O emission at continental level. At country level, N fertilizer application and multi-factor interaction made large contribution to N2O emission increase in the United States of America (USA). The climate variability dominated the increase in N2O emission from Canada. N inputs and multiple factors interaction made large contribution to the increases in N2O emission from Mexico. Central and southeastern parts of the North America - including central Canada, central USA, southeastern USA, and all of Mexico - experienced increases in N2O emission from 1979 to 2010. The fact that climate variability and multi-factor interaction largely controlled the inter-annual variations in terrestrial N2O emission at both continental and country levels indicate that projected changes in the global climate system may substantially alter the regime of N2O emission from terrestrial ecosystems during the 21st century. Our study also showed that the interactive effect among global change factors may significantly affect N2O flux, and more field experiments involving multiple factors are urgently needed.
  • Authors:
    • Kurz, W. A.
    • Birdsey, R. A.
    • McConkey, B. G.
    • Dejong, B.
    • Heath, L. S.
    • West, T. O.
    • Wei, Y. X.
    • McGuire, A. D.
    • Stinson, G.
    • Turner, D. P.
    • Hayes, D. J.
    • Jacobson, A. R.
    • Huntzinger, D. N.
    • Pan, Y. D.
    • Post, W. M.
    • Cook, R. B.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 4
  • Year: 2012
  • Summary: We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000-2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO 2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a -327252 TgC yr -1 sink for NA was driven primarily by CO 2 uptake in the Forest Lands sector (-248 TgC yr -1), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (-297 TgC yr -1), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr -1), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated to be a small net source (+18 TgC yr -1) due to land use change between 1993 and 2002. We compare these inventory-based estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is -511 TgC yr -1 and -931 TgC yr -1, respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO 2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional -239 TgC yr -1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.
  • Authors:
    • Perales, H. R.
    • Martinez-Meyer, E.
    • Ureta, C.
    • Alvarez-Buylla, E. R.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 3
  • Year: 2012
  • Summary: Climate change is expected to be a significant threat to biodiversity, including crop diversity at centers of origin and diversification. As a way to avoid food scarcity in the future, it is important to have a better understanding of the possible impacts of climate change on crops. We evaluated these impacts on maize, one of the most important crops worldwide, and its wild relatives Tripsacum and Teocintes. Maize is the staple crop in Mexico and Mesoamerica, and there are currently about 59 described races in Mexico, which is considered its center of origin. In this study, we modeled the distribution of maize races and its wild relatives in Mexico for the present and for two time periods in the future (2030 and 2050), to identify the potentially most vulnerable taxa and geographic regions in the face of climate change. Bioclimatic distribution of crops has seldom been modeled, probably because social and cultural factors play an important role on crop suitability. Nonetheless, rainfall and temperature still represent a major influence on crop distribution pattern, particularly in rainfed crop systems under traditional agrotechnology. Such is the case of Mexican maize races and consequently, climate change impacts can be expected. Our findings generally show significant reductions of potential distribution areas by 2030 and 2050 in most cases. However, future projections of each race show contrasting responses to climatic scenarios. Several evaluated races show new potential distribution areas in the future, suggesting that proper management may favor diversity conservation. Modeled distributions of Tripsacum species and Teocintes indicate more severe impacts compared with maize races. Our projections lead to in situ and ex situ conservation recommended actions to guarantee the preservation of the genetic diversity of Mexican maize.
  • Authors:
    • Luna-Guido, M.
    • Dendooven, L.
    • del Rosario Cardenas-Aquino, M.
    • Diaz-Rojas, M.
    • Aguilar-Chavez, A.
  • Source: Soil Biology and Biochemistry
  • Volume: 52
  • Issue: September
  • Year: 2012
  • Summary: Applying biochar to soil is an easy way to sequester carbon in soil, while it might reduce greenhouse gas (GHG) emissions and stimulate plant growth. The effect of charcoal application (0, 1.5, 3.0 and 4.5%) on GHG emission was studied in a wastewater sludge-amended arable soil (Typic Fragiudepts) cultivated with wheat (Triticum spp. L) in a greenhouse. The application of charcoal at >= 1.5% reduced the CO2 emission rate significantly >= 37% compared to unamended soil (135.3 g CO2 ha(-1) day(-1)) in the first two weeks, while the N2O emission rate decreased 44% when 4.5% charcoal was added (0.72 g N2O ha(-1) day(-1)). The cumulative GHG emission over 45 days was 2% lower when 1.5% charcoal, 34% lower when 3.0% charcoal and 39% lower when 4.5% charcoal was applied to the sludge-amended soil cultivated with wheat. Wheat growth was inhibited in the charcoal-amended soil compared to the unamended soil, but not yields after 135 days. It was found that charcoal addition reduced the emissions of N2O and CO2, and the cumulative GHG emissions over 45 days, without altering wheat yield. (C) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Vasquez-Murrieta, S.
    • Gutierrez-Miceli, F. A.
    • Montes-Molina, J.
    • Marsch, R.
    • Luna-Guido, M.
    • Verhulst, N.
    • Ramirez-Villanueva, D. A.
    • Patino-Zuniga, L.
    • Gutierrez-Oliva, V. F.
    • Dendooven, L.
    • Govaerts, B.
  • Source: Science of The Total Environment
  • Volume: 431
  • Issue: August
  • Year: 2012
  • Summary: In 1991, the 'International Maize and Wheat Improvement Center' (CIMMYT) started a field experiment in the rain fed Mexican highlands to investigate conservation agriculture (CA) as a sustainable alternative for conventional maize production practices (CT). CT techniques, characterized by deep tillage, monoculture and crop residue removal, have deteriorated soil fertility and reduced yields. CA, which combines minimum tillage, crop rotations and residue retention, restores soil fertility and increases yields. Soil organic matter increases in CA compared to CT, but increases in greenhouse gas emissions (GHG) in CA might offset the gains obtained to mitigate global warming. Therefore, CO2, CH4 and N2O emissions, soil temperature, C and water content were monitored in CA and CT treatments in 2010-2011. The cumulative GHG emitted were similar for CA and CT in both years, but the C content in the 0-60 cm layer was higher in CA (117.7 Mg C ha(-1)) than in CT (69.7 Mg C ha(-1)). The net global warming potential (GWP) of CA (considering soil C sequestration, GHG emissions, fuel use, and fertilizer and seeds production) was -7729 kg CO2 ha(-1) y(-1) in 2008-2009 and -7892 kg CO2 ha(-1) y(-1) in 2010-2011, whereas that of CT was 1327 and 1156 kg CO2 ha(-1) y(-1). It was found that the contribution of CA to GWP was small compared to that of CT. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Marsch, R.
    • Luna-Guido, M.
    • Verhulst, N.
    • Patino-Zuniga, L.
    • Dendooven, L.
    • Govaerts, B.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 152
  • Issue: May
  • Year: 2012
  • Summary: Conservation agriculture based on (1) minimal soil movement, (2) retention of rational amounts of crop residue, (3) economically viable crop rotations restores soil fertility. Conservation agriculture improves soil characteristics, but it remains to be seen how zero tillage (ZT) affected greenhouse gas emissions (GHG) and the global warming potential (GWP) compared to conventional tillage (Cr) when crop residue was kept or removed in a maize-wheat crop rotation since 1991. The soil organic C content in the 0-60 cm layer was larger in ZT (117.7 Mg C ha(-1)) compared to CT (76.8 Mg C ha(-1)) when residue was retained, but similar when it was removed. Tillage and residue management had only a small effect on GWP of the GHG emissions. However, the C sequestered in the 0-60cm was affected by tillage and crop residue management, resulting in a negative net GWP for ZT with crop residue retention (-6.277 Mg CO2 ha(-1) y(-1)) whereas in the other management practices it ranged from 1.288 to 1.885 Mg CO2 ha(-1) y(-1). It was found that cultivation technique had little effect on the GWP of the GHG, but had a large effect on C sequestered in the 0-60cm layer and the net GWP. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Cervantes-Santiago, F.
    • Reyes-Varela, V.
    • Conde, E.
    • Fernandez-Luqueno, F.
    • Juarez-Rodriguez, J.
    • Botello-Alvarez, E.
    • Cardenas-Manriquez, M.
    • Dendooven, L.
  • Source: Journal of Plant Nutrition
  • Volume: 35
  • Issue: 4
  • Year: 2012
  • Summary: Sludge derived from cow manure anaerobically digested to produce biogas (methane; CH4) was applied to maize (Zea mays L.) cultivated in a nutrient-low, alkaline, saline soil with electrolytic conductivity 9.4 dS m(-1) and pH 9.3. Carbon dioxide (CO2) emission increased 3.1 times when sludge was applied to soil, 1.6 times when cultivated with maize and 3.5 times in sludge-amended maize cultivated soil compared to the unamended uncultivated soil (1.51 mg C kg(-1) soil day(-1)). Nitrous oxide (N2O) emission from unamended soil was -0.0004 mu g nitrogen (N) kg(-1) soil day(-1) and similar from soil cultivated with maize (0.27 mu g N kg(-1) soil day(-1)). Application of sludge increased the N2O emission to 4.59 mu g N kg(-1) soil day(-1), but cultivating this soil reduced it to 2.42 mu g N kg(-1) soil day(-1). It was found that application of anaerobic digested cow manure stimulated maize development in an alkaline saline soil and increased emissions of CO2 and N2O.
  • Authors:
    • Villar Sanchez, B.
    • Gonzalez Estrada, A.
    • Livera Munoz, M.
    • Cortes Flores, J. I.
    • Turrent Fernandez, A.
    • Camas Gomez, R.
    • Lopez Martinez, J.
    • Espinoza Paz, N.
    • Cadena Iniguez, P.
  • Source: Revista Mexicana de Ciencias Agricolas
  • Volume: 3
  • Issue: 2
  • Year: 2012
  • Summary: In Chiapas, Mexico, soil erosion is the main problem affecting the sustainability of hillside lands. As a result, yields and incomes are low, and soil quality continues to decrease. With the aim of finding sustainable technological alternatives, an evaluation was performed on the following systems: maize in conservation tillage (MLC); maize in plant barriers (MBMV) and maize alternated with fruit trees (MIAF), in terms of surface runoff, production of sediments and loss of nitrogen and phosphorous from June to November, 2009. The systems were setup in adjacent microbasins, belonging to the basin of river Catarina, Jiquipilas, Chiapas. The soil is a Typic haplustepts, with a slope that varies between 30 and 40%. Out of the total rainfalls, 54% caused soil erosion, 15% of these with rains of over 40 mm 62% of the total erosion. The runoff coefficient and the specific soil degradation were similar and lower in the micro basins; MIAF (12,5.8 t ha -1) and MBMV (13,6.3 t ha -1) than in the microbasin with MLC (19,16.8 t ha -1), respectively. In MIAF, the runoff filter and total cover provided by maize and bean plants during most of the growth season played an important part in obtaining these results, despite this microbasin presenting a greater slope steepness and length. In regards to the nutrients, there was a greater loss of nitrates in the microbasin with the system MBMV, possibly due to the nitrogen contribution by the leftovers of the pruning of Gliricidia sepium. In regard to phosphorous, the system MIAF displayed a greater loss, caused by the yearly phosphoric fertilization performed on the guava trees for three years.
  • Authors:
    • Hellin, J.
    • Wall, P.
    • Sayre, K.
    • Erenstein, O.
    • Dixon, J.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 1-2
  • Year: 2012
  • Summary: Conservation agriculture's underlying principles-minimal soil disturbance, soil cover and crop rotation-are increasingly recognized as essential for sustainable agriculture. This article summarizes three contrasting cases of adapting conservation agriculture (CA) to smallholder conditions in the (sub)tropics: a) irrigated rice-wheat systems in South Asia; b) rainfed maize/wheat and irrigated wheat systems in Mexico; and c) rainfed maize in Southern Africa. In the South Asia case, farm surveys show rapid and widespread adoption of zero tillage wheat-primarily due to a substantial cost saving (15-16%). In the other cases, uptake so far has been limited-although long-term trials show continuously higher and more stable yields both for maize and wheat. Under marginal conditions CA can generate substantial yield increases-averaging some 50% over conventional smallholder maize yields of 1 ton per ha over 6 years in on-farm trails in Southern Africa. The diverse experiences attest to the wide adaptability of CA systems, which can generate clear economic and potentially enormous environmental benefits. The case studies and wider literature however also reiterate the substantial challenges in terms of targeting, adapting and adopting CA-particularly for smallholders in the (sub)tropics. CA systems are best developed in situ through a multi-stakeholder adaptive learning process to create viable CA-based options that are technically sound, economically attractive, and socially acceptable.
  • Authors:
    • Ortega, A. L.
  • Source: Archives of Agronomy and Soil Science
  • Volume: 57
  • Issue: 6
  • Year: 2011
  • Summary: The permanent bed planting system for wheat ( Triticum aestivum L.) production has recently received additional attention. Studies using hard red spring wheat (cultivar Nahuatl F2000) were conducted at two locations in central Mexico. The studies included the installation of three furrow diking treatments, two granular N timing treatments and three foliar N rates applied at the end of anthesis. The objective was to evaluate the effect of these factors on wheat grain yield, yield components and grain N in a wheat-maize ( Zea maize L.) rotation with residues of both crops left as stubble. Results indicated that diking in alternate furrows increased both grain yield and the final number of spikes per m 2. The split application of N fertilizer enhanced the number of spikes per m 2 and grain N uptake, but the effect on grain yield was inconsistent. Similarly, grain protein increased with the foliar application of 6 kg N ha -1, depending upon the maximum temperature within the 10 days following anthesis. The normalized difference vegetative index (NDVI) readings collected at four growth stages were generally higher for the split N application than for the basal N application at planting. Grain N uptake was associated to NDVI readings collected after anthesis.