Posts Tagged ‘climate change’

An innovation systems approach to enhanced farmer adoption of climate-ready germplasm and agronomic practices.

Posted by Carelia Juarez on , in Journal Articles

Published in CAPRi Working Paper. No. 116, 2014

Hellin, J.; Beuchelt, T.; Camacho, C.; Badstue, L.; Govaerts, B.; Donnet, L.; Riis-Jacobsen, J.

By 2050, climate change is likely to reduce maize production globally by 3–10 percent and wheat production in developing countries by 29–34 percent. Even without climate change, the real costs of wheat and maize will increase by 60 percent between 2000 and 2050; climate change could make the figure substantially greater. Food security, despite the above, may be possible if agricultural systems are transformed through improved seed, fertilizer, land use, and governance.

 

Greenhouse gas emissions from nontilled, permanent raised, and conventionally tilled beds in the Central Highlands of Mexico

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Crop Improvement 28 (4) : 547-574, 2014

Dendooven, L.Patiño-Zuñiga, L.Verhulst, N.Boden, K.Garcia-Gaytan, A.Luna-Guido, M.;Govaerts, B.

Organic matter content increases in soil with no-tilled permanent raised beds (PBs) compared with soil with conventionally tilled beds (CBs), and this might affect greenhouse gas (GHG) emissions. Greenhouse gas (CO2, N2O, and CH4) emissions were measured from PBs, from which crop residue was either removed or retained and from CBs where crop residue was retained. The CO2emission was not affected by tillage, but CH4 and N2O emissions were lower in PBs when residue was retained than in CBs. Removing crop residue from PBs reduced CO2 emissions compared with when it was retained, but it had no effect on N2O and CH4 emissions. The global warming potential (GWP) of GHG emissions was higher in CBs (801 kg CO2/ha/year) than in PBs (517 kg CO2/ha/year) with crop-residue retention, but more C was sequestered in the 0–60 cm soil layer in PBs (83.4 Mg C/ha) than in CBs (79.2 Mg C/ha). Crop-residue removal in PBs had little effect on the GWP of GHG compared with PBs with crop residue retained, but less C was sequestered in the latter (63.1 Mg C/ha). Net GWP (considering soil C sequestration, GHG emissions, fuel used, glyphosate application, fertilizer and seed production) was lower in CBs with crop-residue retention (1062 kg CO2/ha/year) than in PBs with crop-residue removal (6,120 kg CO2/ha/year), but it was larger than in PBs with crop-residue retention (−681 kg CO2/ha/year). We found that reduced tillage when beds were made permanent and crop-residue retention greatly reduced net GWP compared with when beds were tilled and remade each year.We found that retention of crop residue in PBs increased the emission of CO2 compared with where it was removed, but tillage did not affect fluxes of CO2. Emission of CH4 and N2O was larger from CBs than from PBs, but crop-residue management in PBs had no significant effect on fluxes of CH4 and N2O. Concentrations of mineral N were larger in CBs than in PBs, whereas the removal of crop residue from PBs increased mineral N concentration. Soil temperature was higher in CBs than in PBs and in PBs with crop residue retained compared with where it was removed. Soil water was better preserved in PBs than in CBs and in PBs where residue was retained than where it was removed. The higher water content in the PB compared with the CB will favor plant growth during dry spells. However, retaining crop residues in PBs will require sufficient application of inorganic N, as mineral N in soil is lower in PBs than in CBs or PBs with crop residue removed. Limited N availability in PBs with crop residue retained might reduce yields as poor farmers in the central highlands of Mexico apply little or no N fertilizer. Reduced tillage on PBs and crop-residue retention strongly reduced the net GWP of the system compared with the case when beds were remade each year. PBs with residue retention reduced net GWP by 50% compared with CBs with residue retention, but the removal of residues from the PBs more than doubled it.

DSSAT modelling of conservation agriculture maize response to climate change in Malawi

Posted by Carelia Juarez on , in Journal Articles

Published in Soil and Tillage Research 143 : 85-94, 2014

Ngwira, A.R.Aune, J.B.Thierfelder, C.

Adoption of conservation agriculture (CA) is increasingly being promoted as a way of adapting agricultural systems to increasing climate variability, especially for areas such as southern Africa where rainfall is projected to decrease. The DSSAT crop simulation models can be a valuable tool in evaluating the effects of CA which are viable both economically and environmentally. Our objectives were: (1) to evaluate the ability of DSSAT to predict continuous maize (Zea mays L.) yield for conventional tillage (CT) and CA systems as well as maize yield for a CA maize–cowpea (Vigna unguiculata) rotation on an Oxic rhodustalf (2) to use DSSAT to project weather effect of climate change on yield, economic returns and risk in CT and CA systems. The DSSAT model was calibrated using data from 2007–2008 season and validated against independent data sets of yield of 2008–2009 to 2011–2012 seasons. Simulations of maize yields were conducted on projected future weather data from 2010 to 2030 that was generated by RegCM4 using the A1B scenario. The DSSAT model calibration and validation showed that it could be used for decision-making to choose specific CA practices especially for no-till and crop residue retention. Long term simulations showed that maize–cowpea rotation gave 451 kg ha−1 and 1.62 kg mm−1 rain more maize grain yield and rain water productivity, respectively compared with CT. On the other hand, CT (3131–5023 kg ha−1) showed larger variation in yield than both CA systems (3863 kg ha−1 and 4905 kg ha−1). CT and CA systems gave 50% and 10% cumulative probability of obtaining yield below the minimum acceptable limit of 4000 kg ha−1respectively suggesting that CA has lower probability of low yield than CT, thus could be preferred by risk-averse farmers in uncertain climatic conditions. Using similar reasoning, Mean-Gini Dominance analysis showed the dominancy of maize–cowpea rotation and indicated it as the most efficient management system. This study therefore suggests that CA, especially when all three principles are practiced by smallholders in the medium altitude of Lilongwe and similar areas, has the potential to adapt the maize based systems to climate change. Use of DSSAT simulation of the effects of CA was successful for no-till and crop residue retention, but poor for crop rotation. Refinement of crop rotation algorithm in DSSAT is recommended.

Effects of tillage and crop residue management on maize yields and net returns in the Central Mexican highlands under drought conditions

Posted by Carelia Juarez on , in Journal Articles

Published in Pedosphere 24 (4476-486, 2014

Romero-Perezgrovas, R.R.Verhulst, N.De la Rosa, D.Hernandez, V.Maertens, M.Deckers, J.Govaerts, B.

In the subtropical highlands of Central Mexico, where the main crop is maize (Zea mays), the conventional practice (CP) involves tillage, monoculture and residue removal, leading to soil degradation and unsustainable use of natural resources and agricultural inputs. Conservation agriculture (CA) has been proposed as a viable alternative in the region, based on reduction in tillage, retention of adequate levels of crop residues and soil surface cover and use of crop rotation. This study began in 2009 when the highlands of Central Mexico suffered from a prolonged drought during vegetative maize growth in July–August, providing an opportunity for the on-farm comparison of CA with CP under severe drought conditions which 21 climate change models projected to become more frequent. Under dry conditions, CA resulted in higher yields and net returns per hectare as early as the first and second years after adoption by farmers. As an average of 27 plots under farmers’ management in 2009, the maize yields were 26% higher under CA (6.3 t ha−1) than under CP (5.0 t ha−1). 2010 was close to a normal year in terms of rainfall so yields were higher than in 2009 for both practices; in addition, the yield difference between the practices was reduced to 19% (6.8 t ha−1 for CA vs.5.7 t ha−1 for CP). When all the 2009 and 2010 observations were analyzed in a modified stability analysis, CA had an overall positive effect of 3 838 Mexican Pesos ha−1 (320 $US ha−1) on net return and 1.3 t ha−1 on yield. After only one to two years of adoption by farmers on their fields, CA had higher yields and net returns under dry conditions that were even drier than those predicted by the analyzed 21 climate change models under a climate change scenario, emission scenario A2.

Nodule performance within a changing environmental context

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Plant Physiology 171 (12) : 1076-1090, 2014

Aranjuelo, I.Arrese-Igor, C.Molero, G.

Global climate models predict that future environmental conditions will see alterations in temperature, water availability and CO2 concentration ([CO2]) in the atmosphere. Climate change will reinforce the need to develop highly productive crops. For this purpose it is essential to identify target traits conditioning plant performance in changing environments. N2 fixing plants represent the second major crop of agricultural importance worldwide. The current review provides a compilation of results from existing literature on the effects of several abiotic stress conditions on nodule performance and N2 fixation. The environmental factors analysed include water stress, salinity, temperature, and elevated [CO2]. Despite the large number of studies analysing [CO2] effects in plants, frequently they have been conducted under optimal growth conditions that are difficult to find in natural conditions where different stresses often occur simultaneously. This is why we have also included a section describing the current state of knowledge of interacting environmental conditions in nodule functioning. Regardless of the environmental factor considered, it is evident that some general patterns of nodule response are observed. Nodule carbohydrate and N compound availability, together with the presence of oxygen reactive species (ROS) have proven to be the key factors modulating N2 fixation at the physiological/biochemical levels. However, with the exception of water availability and [CO2], it should also be considered that nodule performance has not been characterised in detail under other limiting growth conditions. This highlights the necessity to conduct further studies considering these factors. Finally, we also observe that a better understanding of these metabolic effects of changing environment in nodule functioning would require an integrated and synergistic investigation based on widely used and novel protocols such as transcriptomics, proteomics, metabolomics and stable isotopes.

An assessment of wheat yield sensitivity and breeding gains in hot environments

Posted by Carelia Juarez on , in Journal Articles

Published in Proceedings of the Royal Society B: Biological Sciences 280 (1752) : 1-8, 2013

Gourdji, S.M.; Mathews, K.L.;Reynolds, M.P.; Crossa, J.; Lobell, D.B.

Genetic improvements in heat tolerance of wheat provide a potential adaptation response to long-term warming trends, and may also boost yields in wheat-growing areas already subject to heat stress. Yet there have been few assessments of recent progress in breeding wheat for hot environments. Here, data from 25 years of wheat trials in 76 countries from the International Maize and Wheat Improvement Center (CIMMYT) are used to empirically model the response of wheat to environmental variation and assess the genetic gains over time in different environments and for different breeding strategies. Wheat yields exhibited the most sensitivity to warming during the grain-filling stage, typically the hottest part of the season. Sites with high vapour pressure deficit (VPD) exhibited a less negative response to temperatures during this period, probably associated with increased transpirational cooling. Genetic improvements were assessed by using the empirical model to correct observed yield growth for changes in environmental conditions and management over time. These ‘climate-corrected’ yield trends showed that most of the genetic gains in the high-yield-potential Elite Spring Wheat Yield Trial (ESWYT) were made at cooler temperatures, close to the physiological optimum, with no evidence for genetic gains at the hottest temperatures. In contrast, the Semi-Arid Wheat Yield Trial (SAWYT), a lower-yielding nursery targeted at maintaining yields under stressed conditions, showed the strongest genetic gains at the hottest temperatures. These results imply that targeted breeding efforts help us to ensure progress in building heat tolerance, and that intensified (and possibly new) approaches are needed to improve the yield potential of wheat in hot environments in order to maintain global food security in a warmer climate.

Crops that feed the world 10. Past successes and future challenges to the role played by wheat in global food security

Posted by Carelia Juarez on , in Journal Articles

Published in Food Security 5 (3) : 291-317, 2013

Shiferaw, B.; Smale, M.; Braun, H.J.; Duveiller, E.; Reynolds, M.P.; Muricho, G.

Wheat is fundamental to human civilization and has played an outstanding role in feeding a hungry world and improving global food security. The crop contributes about 20 % of the total dietary calories and proteins worldwide. Food demand in the developing regions is growing by 1 % annually and varies from 170 kg in Central Asia to 27 kg in East and South Africa. The developing regions (including China and Central Asia) account for roughly 53 % of the total harvested area and 50 % of the production. Unprecedented productivity growth from the Green Revolution (GR) since the 1960s dramatically transformed world wheat production, benefitting both producers and consumers through low production costs and low food prices. Modern wheat varieties were adopted more rapidly than any other technological innovation in the history of agriculture, recently reaching about 90 % of the area in developing regions. One of the key challenges today is to replace these varieties with new ones for better sustainability. While the GR “spared” essential ecosystems from conversion to agriculture, it also generated its own environmental problems. Also productivity increase is now slow or static. Achieving the productivity gains needed to ensure food security will therefore require more than a repeat performance of the GR of the past. Future demand will need to be achieved through sustainable intensification that combines better crop resistance to diseases and pests, adaptation to warmer climates, and reduced use of water, fertilizer, labor and fuel. Meeting these challenges will require concerted efforts in research and innovation to develop and deploy viable solutions. Substantive investment will be required to realize sustainable productivity growth through better technologies and policy and institutional innovations that facilitate farmer adoption and adaptation. The enduring lessons from the GR and the recent efforts for sustainable intensification of cereal systems in South Asia and other regions provide useful insights for the future.

Trends in daily observed temperature and precipitation extremes over three Ethiopian eco-environments

Posted by Carelia Juarez on , in Journal Articles

Published in International Journal of Climatology, 2013

Aklilu Mekasha; Kindie Tesfaye Fantaye; Duncan, A.J.

Ethiopia has wide eco-environmental diversity ranging from extreme heat at one of the lowest places in the world to one of the coolest summits in Africa. Associated with this environmental diversity and climate change, climatic extremes are expected to change over time and also vary across eco-environments in the country. This study was conducted to examine the trends of past precipitation and temperature extremes over three eco-environments in Ethiopia. The study involved analysis of 20 extreme indices computed from daily temperature and precipitation data spanning over 42 years (1967–2008). The climate data were obtained from 11 stations selected from three major eco-environments (pastoral, agropastoral and highland). The results indicated positive trends for maximum value of the maximum temperature (TXx), warm days (TX90p), warm nights (TN90p) and warm spell duration indicators (WSDI) and negative trends for cool days (TX10p), cool nights (TN10p) and cold spell duration indicators (CSDI) in more than 8 of the 11 stations studied. However, most of the trends were not significant at many of the stations and the significant trends were not uniquely differentiated by eco-environments. Unlike temperature extremes, precipitation extreme trends showed high variability among nearby stations within eco-environments and were not significant at many of the stations studied. It is concluded that trends of temperature and precipitation extremes vary considerably among stations located within a given eco-environment indicating that the response of local climate to global warming could be different in physiographically diverse regions.

Identificacion de razas mexicanas de maiz adaptadas a condiciones deficientes de humedad mediante datos biogeograficos. Identification of Mexican maize races adapted to moisture deficient conditions using biogeographical data

Posted by Carelia Juarez on , in Journal Articles

Published in Revista Mexicana de Ciencias Agricolas 4 (6) : 829-842, 2013

José Ariel Ruiz Corral, José de Jesús Sánchez González, Juan Manuel Hernández Casillas, Martha C. Willcox, Gabriela Ramírez Ojeda, José Luis Ramírez Díaz y Diego Raymundo González Eguiarte

Se trabajó con una base de datos de accesiones recientes  de 54 razas de maíz de México, cuyos datos pasaporte se  extrajeron de la Unidad de Recursos Genéticos del Banco  de Germoplasma del INIFAP. A partir de las coordenadas  geográficas de las accesiones, se hizo una caracterización  por sitios de accesión, de las condiciones de disponibilidad de humedad del período mayo-octubre para el desarrollo del maíz, con base en el sistema de información ambiental del INIFAP y el sistema IDRISI Andes. Con estos datos se realizó un análisis estadístico que incluyó análisis de varianza y un análisis de taxonomía numérica (análisis cluster) con la opción de correlación de momento producto entre razas. Adicionalmente se realizó un análisis de accesiones por raza para identificar las accesiones que desarrollan bajo ambientes con deficiencia de humedad. Se seleccionaron las accesiones con adaptación a un ambiente con índice de humedad (IH) (precipitación/evapotranspiración potencial) mayo-octubre inferior a 0.5. Los resultados mostraron la identificación de cinco grupos raciales, de los cuales uno de ellos se destacó por su adaptación a un IH entre 0.39 y 0.53. Este grupo incluyó las razas Chapalote, Dulcillo del Noroeste, Tuxpeño Norteño, Cónico Norteño, Tablilla de Ocho y Gordo. El análisis de accesiones reportó la presencia de maíz en un total de 677 sitios con condiciones de semiaridez en la temporada mayo-octubre. Las 677 accesiones representan a 24 razas. Éstos resultados permiten concluir que en México existen recursos genéticos, relacionados con las razas de maíz, los cuales podrían ser de utilidad en los programas de mejoramiento genético de maíz enfocados a la adaptación a estrés por sequía.

Adapting maize production to climate change in sub-Saharan Africa

Posted by Carelia Juarez on , in Journal Articles

Published in Food Security, 2013

Jill E. Cairns, Jon Hellin, Kai Sonder, José Luis Araus, John F. MacRobert, Christian Thierfelder and  B. M. Prasanna

Given the accumulating evidence of climate change in sub-Saharan Africa, there is an urgent need to develop more climate resilient maize systems. Adaptation strategies to climate change in maize systems in sub-Saharan Africa are likely to include improved germplasm with tolerance to drought and heat stress and improved management practices. Adapting maize systems to future climates requires the ability to accurately predict future climate scenarios in order to determine agricultural responses to climate change and set priorities for adaptation strategies. Here we review the projected climate change scenarios for Africa’s maize growing regions using the outputs of 19 global climate models. By 2050, air temperatures are expected to increase throughout maize mega- environments within sub-Saharan Africa by an average of 2.1°C. Rainfall changes during the maize growing season varied with location. Given the time lag between the development of improved cultivars until the seed is in the hands of farmers and adoption of new management practices, there is an urgent need to prioritise research strategies on climate change resilient germplasm development to offset the predicted yield declines.