• Authors:
    • Zhang, J.
    • Li, B.
    • Xie, G.-L.
    • Cui, Z.-Q.
    • Ojaghian, M. R.
  • Source: Australasian Plant Pathology
  • Volume: 41
  • Issue: 4
  • Year: 2012
  • Summary: This study was conducted to evaluate the potential of biofumigation in three Brassica crops including Brassica napus, Brassica juncea and Brassica campestris against potato stem rot caused by Sclerotinia sclerotiorum in field tests. Results from field trials carried out in three naturally infected potato fields during three cropping seasons of 2008-2010 showed that the Brassica crops used as green manure cover crops were able to significantly reduce disease incidence and mean percentage of dead plants (as a proportion of infected plants). Although results varied somewhat by field site and year, B. juncea generally provided the highest level of control, averaging greater than 55.6 % reduction in disease incidence over all fields and years, compared to average disease reductions of 31.6 and 45.8 % for the B. napus and B. campestris crop treatments, respectively. Furthermore reduction of dead plants averaged 61.6, 39.2 and 32.1 % for B. juncea, B. napus, and B. campestris, respectively. In this study, Brassica crops showed various significant inhibitory effects in different fields and years indicating that disease development is affected by other factors including environmental conditions.
  • Authors:
    • Roostaee, M.
    • Liaghat, A.
    • Parsinejad, M.
    • Tabrizi, M. S.
    • Nahvinia, M.
  • Source: International Journal of Agriculture: Research and Review
  • Volume: 2
  • Issue: 3
  • Year: 2012
  • Summary: Sustainable irrigated agriculture entails monitoring water, salt balance and effective depth of root zone. A lysimeter study was based absorption of plant water requirement beyond predefined root depth. Experiment was conducted with three treatments in three replications at the research field of the University of Tehran in Karaj, Iran, in 2007 on soybean including: treatment A at MAD (Maximum Allowable Depletion) of 55%, treatment B at MAD=65% and treatment C also at MAD=65% but with 30% excess irrigation. The results showed in treatment C crop yield not only did not significantly decrease as compared with treatment A but water application efficiency increased by 11.2%. Water extraction of plants at the deeper soil layers in response to longer irrigation intervals can result in increased plant water uptake efficiency.
  • Authors:
    • Saoub, H. M.
    • Akash, M. W.
    • Ayad, J. Y.
  • Source: Research on Crops
  • Volume: 13
  • Issue: 1
  • Year: 2012
  • Summary: In Jordan, the improvement of vetch production is becoming one of the main objectives as its growing areas are decreasing either because of environmental or cropping system changes. However, there is no literature concerning the assessment of genetic diversity of vetches landraces that harbour important genes for the development of new adapted varieties. The present study aimed at collecting, evaluating and characterizing vetch landraces covering different parts of Jordan. Twenty-six vetch landraces were collected from different parts of Jordan during a period extended from April to May in 2006-07 growing season and assessed in the field during 2008-09 growing season. The experiment was conducted at three stations (Ghwier Agricultural Research Station, Rabba Agricultural Research Station and Jubeiha Agricultural Research Station, The University of Jordan). Results indicated that grain yield of Vicia erivillia landraces was higher than grain yield of Vicia sativa landraces, regardless of the growing location. However, biological yield obtained from V. sativa entries [671 kg/ha (entry no. 6) upto 2514 kg/ha (entry no. 1)] was higher than that obtained from V. erivillia entries [536 kg/ha (entry no. 10) upto 2125 kg/ha (entry no. 23)]. Similar trend was shown for straw yield where V. sativa entries had more vegetative growth compared to V. erivillia entries. These differences attributed to the dissimilarity in genetic make-up of the two species. For example, some researchers mention that V. erivillia produces more grain yield due to its ability to tolerate drought when compared to V. sativa. The identification of these superior adapted local landraces is the first step in fulfilling the objective of the national vetch breeding programme.
  • Authors:
    • Stewart, J. S.
    • Menge, B. A.
    • Gouhier, T. C.
    • Iles, A. C.
    • Haupt, A. J.
    • Lynch, M. C.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 2
  • Year: 2012
  • Summary: Eastern boundary current systems are among the most productive and lucrative ecosystems on Earth because they benefit from upwelling currents. Upwelling currents subsidize the base of the coastal food web by bringing deep, cold and nutrient-rich water to the surface. As upwelling is driven by large-scale atmospheric patterns, global climate change has the potential to affect a wide range of significant ecological processes through changes in water chemistry, water temperature, and the transport processes that influence species dispersal and recruitment. We examined long-term trends in the frequency, duration, and strength of continuous upwelling events for the Oregon and California regions of the California Current System in the eastern Pacific Ocean. We then associated event-scale upwelling with up to 21 years of barnacle and mussel recruitment, and water temperature data measured at rocky intertidal field sites along the Oregon coast. Our analyses suggest that upwelling events are changing in ways that are consistent with climate change predictions: upwelling events are becoming less frequent, stronger, and longer in duration. In addition, upwelling events have a quasi-instantaneous and cumulative effect on rocky intertidal water temperatures, with longer events leading to colder temperatures. Longer, more persistent upwelling events were negatively associated with barnacle recruitment but positively associated with mussel recruitment. However, since barnacles facilitate mussel recruitment by providing attachment sites, increased upwelling persistence could have indirect negative impacts on mussel populations. Overall, our results indicate that changes in coastal upwelling that are consistent with climate change predictions are altering the tempo and the mode of environmental forcing in near-shore ecosystems, with potentially severe and discontinuous ramifications for ecosystem structure and functioning.
  • Authors:
    • Roy-Macauley, H.
    • Jalloh, A.
    • Sereme, P.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 157
  • Year: 2012
  • Summary: The West and Central Africa (WCA) sub region covers a total area of over 11.5 million km 2 with a population of over 318 million. Most of the rural population in WCA are poor and food insecure and about 70% of the people in the region depends on agriculture, which accounts for over 35% of Gross Domestic Product (GDP) and over 40% of its export. The agroecological zones of WCA are closely related to the agro climatic zones of the region with rainfall decreasing from the southern coast in the forest region to the sub humid and semi arid Sahelian region in the north. The major agroecosystems of WCA include the semi arid, sub humid, humid forest, and swamp. Growing populations, inappropriate agricultural practices and changing climate in the region are influencing the composition and ability of agroecosystems in providing much needed ecosystem services. Coordinating efforts to tackle these challenges and leverage opportunities for sustainable agricultural production while ensuring conservation of the diverse ecosystems in the region is therefore a major preoccupation of the West and Central African Council for Agricultural Research and Development (CORAF/WECARD).
  • Authors:
    • Moyo, B. H.
    • Chirwa, P. W.
    • Khumalo, S.
    • Syampungani, S.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 157
  • Year: 2012
  • Summary: This paper reviews the agroecosystems and agricultural biodiversity in Southern Africa and highlights the importance of the agricultural landscape in biodiversity conservation and the important role that the traditional farming systems play in conserving biodiversity. The review established that agrobiodiversity is of great importance to both small scale and large commercial farmers in Southern Africa through its provision of ecosystem services. The paper also highlights the significant loss of agrobiodiversity as a result of human population pressure and the transition from traditional mixed farming systems which is characterized with high agrobiodiversity, to modern monoculture farming resulting in decline of species diversity. Although concerted efforts are being made to promote the sustainable use and management of this agrobiodiversity, there need to have a multi-stakeholder approach so that conservation efforts are successful, a role that is currently played by the SADC Plant Genetic Resources Centre in Southern African conservation of agrobiodiversity.
  • Authors:
    • White, J. W.
    • Kimball, B. A.
    • Ottman, M. J.
    • Wall, G. W.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 1
  • Year: 2012
  • Summary: Possible future increases in atmospheric temperature may threaten wheat (Triticum aestivum L.) production and food security. The purpose of this research is to determine the response of wheat growth to supplemental heating and to seasonal air temperature from an unusually wide range of planting dates. A field study was conducted at Maricopa, AZ, where wheat was planted from September to May over a 2-yr period for a total of 12 planting dates. Supplemental heating was provided for 6 of the 12 planting dates using infrared heaters placed above the crop which increased canopy temperature by 1.3°C during the day and 2.7°C during the night. Grain yield declined 42 g m -2 (6.9%) per 1°C increase in seasonal temperature above 16.3°C. Supplemental heating had no effect on grain yield for plantings in winter (Dec./Jan.) since temperatures were near optimum (14.9°C). However, in spring (Mar.) plantings where temperature (22.2°C) was above optimum, supplemental heating decreased grain yield from 510 to 368 g m -2. Supplemental heating had the greatest effect in the early fall plantings (Sept./Oct.) when temperature was slightly below optimum (13.8°C) and mid-season frost limited the yield of unheated plots to only 3 g m -2 whereas yield of heated plots was 435 g m -2. Thus, possible future increases in temperature may decrease wheat yield for late plantings and shift optimum planting windows to earlier dates in areas of the world similar to the desert southwest of the United States.
  • Authors:
    • Abdeddayem, R.
    • Guefrachi, I.
    • Dhaoui, S.
    • Fterich, A.
    • Mahdhi, M.
    • Rejili, M.
    • Mars, M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 157
  • Year: 2012
  • Summary: Wild legumes (herbs, shrubs or trees) play a critical role in natural ecosystems, agriculture, and agroforestry, where their ability to fix nitrogen in symbiosis makes them excellent colonizers of low-N environments, and hence an economic and environmentally friendly species. The field natural nodulation of the wild Tunisian legumes, the genetic diversity and symbiotic-efficiency of their root nodulating bacteria (RNB) and the dynamics of soil fertility under symbiotic association in arid regions of Tunisia were investigated during this study. Natural nodulation varied according to the species and site. Morphologically, nodules were spindle-shaped ( Trigonella maritima, Hedysarum spinosissimum, Argyrolobium uniflorum, Genista saharae, Retama reteam, Vicia sativa). The colour of the nodules was not related to that of the roots, but depends on soil quality and colour, and on the presence of leghaemoglobin. Based on molecular techniques (16S rRNA sequencing) and phenotypic characteristics, the root-nodule bacteria isolated from the Tunisian wild legumes were classified into four genera ( Rhizobium, Mesorhizobium, Sinorhizobium). No Bradyrhizobium genus was recovered in our results. Non-nodulating bacteria considered as endophytic to nodules were also reported in our results and four genera belonging to Phyllobacterium, Starkeya, Pseudomonas, and Kocuria were taxonomically defined, for Lotus sp. and H. spinosissimum. Bacteria belonging to Sinorhizobium genus were widely distributed in area under study. Wild legumes belonging to Lotus spp., Vicia spp. and Hedysarum spp. were nodulated by this genus. Mesorhizobium genus was restricted to Lotus sp., and Rhizobium genus nodulated Vicia and Lotus. Phenotypically, our results showed that the root nodulating bacteria belonging to the genus Sinorhizobium exhibited higher tolerance to salt stress and elevated temperatures. Based on symbiotic properties, our reports indicated that the wild-legume rhizobia formed effective and successful symbioses with their legume hosts. The diversity and effectiveness of the nitrogen-fixing wild legumes are of major significance to soil fertility dynamics in the arid regions. Effects on enzyme activities, microbial biomass and respiration, were evaluated in different agricultural soils and in the presence of different wild legumes such as G. saharae and R. raetam. Results showed that legumes-rhizobia symbiosis improves enzyme activities, microbial biomass and respiration of field soils and regenerate microbiological properties and the microflora activity involved in the decomposition of organic matter.
  • Authors:
    • Hertig, E.
    • Freier, K. P.
    • Schilling, J.
    • Scheffran, J.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 156
  • Year: 2012
  • Summary: Our study links environmental impacts of climate change to major socio-economic and agricultural developments in North Africa. We jointly investigate climate projections, vulnerability, impacts, and options for adaptation. Precipitation in North Africa is likely to decrease between 10 and 20%, while temperatures are likely to rise between 2 and 3°C by 2050. This trend is most pronounced in the north-western parts of northern Africa as our own model results suggest. The combination of decreasing supply and strong population growth aggravates the stressed water situation in the region. We further compare the vulnerabilities, adaptive capacities and conflict implications of climate change in Algeria, Egypt, Libya, Morocco, and Tunisia. Climate change will likely have the strongest effect on Morocco where the agricultural sector is of high importance for the country's economy and particularly for poor people. Our analysis of climate impacts and adaptation options in Morocco suggests that the agricultural incentives used in the past are inadequate to buffer drought effects. To increase resilience against climate change, agricultural policies should shift from maximizing agricultural output to stabilizing it. Our bio-economic model results further suggest a considerable potential of replacing firewood by electric energy to sustain pastoral productivity.
  • 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.