• Authors:
    • Kelley, J. J.
    • Tans, P. P.
    • Sweeney, C.
    • Welp, L. R.
    • Wofsy, S. C.
    • Stephens, B. B.
    • Patra, P. K.
    • Piper, S. C.
    • Keeling, R. F.
    • Graven, H. D.
    • Daube, B. C.
    • Kort, E. A.
    • Santoni, G. W.
    • Bent, J. D.
  • Source: Report
  • Volume: 341
  • Issue: 6150
  • Year: 2013
  • Summary: Seasonal variations of atmospheric carbon dioxide (CO2) in the Northern Hemisphere have increased since the 1950s, but sparse observations have prevented a clear assessment of the patterns of long-term change and the underlying mechanisms. We compare recent aircraft-based observations of CO2 above the North Pacific and Arctic Oceans to earlier data from 1958 to 1961 and find that the seasonal amplitude at altitudes of 3 to 6 km increased by 50% for 45 degrees to 90 degrees N but by less than 25% for 10 degrees to 45 degrees N. An increase of 30 to 60% in the seasonal exchange of CO2 by northern extratropical land ecosystems, focused on boreal forests, is implicated, substantially more than simulated by current land ecosystem models. The observations appear to signal large ecological changes in northern forests and a major shift in the global carbon cycle.
  • Authors:
    • Sampathkumar, T.
    • Pandian, B. J.
    • Mahimairaja, S.
  • Source: Agricultural Water Management
  • Volume: 103
  • Year: 2012
  • Summary: Field experiments were conducted during 2007-2009 to study the effect of deficit irrigation practices through drip irrigation system on soil moisture distribution and root growth in cotton-maize cropping sequence. Creation of soil moisture gradient is indispensable to explore the beneficial effects of partial root zone drying (PRD) irrigation and it could be possible only through ADI practice in paired row system of drip layout, that is commonly practiced in India. In the present study, PRD and deficit irrigation (DI) concepts (creation of soil moisture gradient) were implemented through alternate deficit irrigation (ADI) at two levels of irrigation using drip system. Experimental treatments comprised of six irrigation levels (full and deficit) through drip system with surface irrigation for comparison. Maize was sown after cotton under no till condition without disturbing the raised bed and drip layout. Roots confined to the shallow depth and recorded the lowest values for both the crops under conventional drip irrigation at 100% ETc. Among the deficit irrigation treatments, mild deficit irrigation produced longer lateral roots from both the sides of the plant. Contrary to rooting depth, severe water stress affected the lateral root spread and recorded lower values than other drip irrigation treatments. Soil moisture content (SMC) was low nearer to the plant (at 30 cm across the lateral) and far away (at 30 cm along the lateral) from the plant, irrespective of treatments. The reduction in SMC was increased at all locations as applied water level decreased. It is concluded that alternate watering imposed through ADI at 100% ETc produced longer lateral roots with higher values for root dry mass Alternate deficit irrigation (ADI) resulted uneven distribution of soil moisture content. Among the ADI treatments, ADI at 100% had less uneven distribution than ADI at 80% ETc.
  • Authors:
    • Roger-Estrade, J.
    • Basch, G.
    • Moreno, F.
    • Soane, B. D.
    • Ball, B. C.
    • Arvidsson, J.
  • Source: Soil & Tillage Research
  • Volume: 118
  • Year: 2012
  • Summary: Recent literature on no-till is reviewed with particular emphasis on research on commercial uptake and environmental concerns in northern, western and south-western Europe. Increased interest in no-till, and minimum or reduced tillage, results from changes in the economic circumstances of crop production, the opportunity to increase the area of more profitable autumn-sown crops and increased concern about environmental damage associated with soil inversion by ploughing. Highly contrasting soil and climate types within and between these regions exert a strong influence on the success of no-till. While no-till may often result in crop yields which equal or exceed those obtained after ploughing, modest reductions in yield may be tolerated if production costs are lower than with ploughing. The relative costs of fuel and herbicides have changed appreciably in recent years making no-till more attractive commercially. While effective weed control is an essential aspect of no-till, current herbicide technology may not yet fully achieve this. In northern regions no-till usually allows earlier drilling of winter-sown crops but will give lower soil temperature and higher moisture content in spring, causing delayed drilling of spring-sown crops. No-till soils have greater bulk density and bearing capacity than ploughed soils with a pronounced vertical orientation of macroporosity allowing penetration of roots and water, especially in view of the increased population of deep-burrowing earthworms. Particular care must be taken with no-till to minimise soil damage at harvest and to ensure the even distribution of crop residues prior to drilling. Reduced erosion and runoff after adoption of no-till are widely observed and are of particular importance in southwestern Europe. No-till reduces losses of phosphorus in runoff and, in some cases, reduces the loss of nitrate through leaching. Emissions of greenhouse gases CO 2 and N 2O from no-till soils are highly variable and depend on complex interactions of soil properties. Emission of CO 2 from fuel during machinery usage is always appreciably reduced with no-till. Increased soil organic carbon in surface layers of no-till soils is widely found but may not be associated with increased carbon sequestration throughout the profile. The evaluation of the relative carbon balance for no-till and ploughing depends upon complex inter-relationships between soil and climate factors which are as yet poorly understood. Adoption of no-till could be encouraged by government financial assistance in recognition of environmental benefits, although future restrictions on the use of herbicides may be a deterrent. Opportunities for further research on no-till are outlined.
  • Authors:
    • Dauber, J.
    • Zimmermann, J.
    • Jones, M. B.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: The use of biomass for energy production is considered a promising way to reduce net carbon emissions and mitigate climate change. However, land-use change to bioenergy crops can result in carbon emissions from soil and vegetation in amounts that could take decades to compensate. Perennial grasses such as Miscanthus offer a possible solution to this problem as measurements on experimental plots planted with Miscanthus have shown significant carbon sequestration in the soil. It can, however, be expected that sequestration potentials in commercial use might differ from those measured in experimental plots due to different farming practices and soil characteristics. For this study, Miscanthus plantations on 16 farms in SE Ireland as well as on-farm controls representing the former land-use (grassland and tillage) have been examined. The Miscanthus plantations were 2-3 years old. Soil organic carbon (SOC) content and a number of soil properties were measured and the amount of Miscanthus-derived carbon was determined using the 13C natural abundance method. On both former tillage fields and grasslands, although there were no significant differences in SOC contents between Miscanthus and control sites, it was shown that 2-3 years after Miscanthus establishment, 1.821.69 and 2.171.73 Mg ha -1 of the SOC under former-tilled and former grassland respectively were Miscanthus-derived. Mixed-effects models were used to link the total SOC concentrations and Miscanthus-derived carbon to the land-use parameters as well as to soil properties. It was shown that on control sites, pH had an effect on total SOC. In the case of Miscanthus-derived carbon, the initial SOC content, pH, former land-use and crop age had significant effects.
  • Authors:
    • Castagnara, D. D.
    • Fey, R.
    • Seidel, E. P.
    • Testa, J. V. P.
    • Steiner, F.
    • Zoz, T.
    • Zoz, A.
  • Source: SEMINA-CIENCIAS AGRARIAS
  • Volume: 33
  • Issue: 2
  • Year: 2012
  • Summary: The objective of this work was to evaluate the effect of foliar application of molybdenum on agronomic characteristics and yield of wheat in a no-till system. The experiment was carried out in a clayey Rhodic Hapludox, in Maripa, State of Parana, Brazil. The experimental design was randomized blocks with five replications. Treatments consisted of four doses of molybdenum (0, 13.8, 27.6 and 55.2 g ha -1 Mo), divided into two foliar applications, the first at tillering (18 days after plant emergence) and the second at the boot stage (65 days after emergence). The foliar application of Mo up to a dose of 35 g ha -1 increased the number of spikes per square meter and yield of wheat; however, it had no effect on the agronomic characteristics of the crop in a no-till system.
  • Authors:
    • Reinhardt, C. F.
    • Bezuidenhout, S. R.
    • Whitwell, M. I.
  • Source: Weed Research
  • Volume: 52
  • Issue: 2
  • Year: 2012
  • Summary: No information is available on the effect of cover crops on weed growth in maize production in KwaZulu-Natal, South Africa. In a field experiment, the influence of two preceding cover crops, stooling rye and annual ryegrass, on the growth of maize and the weed Cyperus esculentus were compared with herbicides and weed control by hoeing. Maize emergence and early growth were delayed in the presence of physical residues of both cover crop species, especially annual ryegrass. Growth of C. esculentus was significantly inhibited in the inter-row maize planting lines by the cover crops for the first 16 days after maize emergence, but this effect had diminished by day 28. In a pot experiment, the influence of the same two cover crops on maize and C. esculentus growth was evaluated together with oats and two additional annual ryegrass cultivars. Here, the growth of maize and C. esculentus were suppressed, especially by the root residues of the annual ryegrass, in particular the cultivar Midmar. Chemical analysis of the leachate of the root residues indicated the presence of phenolic acids and benzoxazolin-2(3 H)-one. To achieve effective weed control, a weed management strategy combining the mulch retained on the soil surface, with a possible reduction in the type and amount of herbicide, should be implemented.
  • Authors:
    • Gerhards, R.
    • Brust, J.
  • Source: Julius-Kuhn-Archiv
  • Volume: 1
  • Issue: 434
  • Year: 2012
  • Summary: Lopsided oat ( Avena strigosa) has been cultivated for many years, especially in Brazil, as a summer annual cover crop. Experiments were conducted in Stuttgart-Hohenheim in 2010 to estimate the capability of lopsided oat, yellow mustard ( Sinapis alba), phacelia ( Phacelia tanacetifolia) and a cover crop mixture to suppress weeds and volunteer wheat. A pot experiment was conducted to analyze the emergence and growth of the different cover crop species. Twelve weeks after planting, lopsided oat produced 20.7 dt/ha of shoot- and 5.5 dt/ha of root dry matter. A field experiment was established in the summer after harvest of winter wheat. The soil was cultivated with a disc harrow and the cover crops were sown one day later. At four week intervals, the plant density and dry matter of cover crops, weeds and volunteer wheat were determined. Twelve weeks after planting, lopsided oat produced 17.8 dt/ha shoot- and 6.2 dt/ha root dry matter. In the lopsided oat plots, shoot dry matter of weeds and volunteer wheat were reduced by 98% compared with control plots without cover crops. This was the highest weed reduction of all cover crops studied. The root dry matter of weeds and volunteer wheat was reduced by 55% to 97% in all cover crops, compared to the control plots. Lopsided oat reduced the plant density of weeds and volunteer wheat. While there were 54.5 plants/m 2 in the control plots, only 5.5 plants/m 2 were counted in the lopsided oat plots. The results showed that lopsided oat has a high potential for suppression of weeds and volunteer wheat in autumn. It also enlarges the number of cultivated cover crops in Central Europe.
  • Authors:
    • Valaci, F.
    • Andrade, L.
    • Fonseca, G.
    • Andrade, M.
    • Carvalho, G.
    • Carvalho, W.
    • Oliveira, D.
  • Source: Revista Brasileira de Biociencias
  • Volume: 10
  • Issue: 1
  • Year: 2012
  • Summary: This study aimed at evaluating the allelopathic effect of species used as cover crops in no-tillage system on common bean crop. It was conducted in the greenhouse and at the Seed Analysis Laboratory in the Agricultural Department of the Federal University of Lavras, Brazil. The cover crop species used in the experiment were sunn hemp, jack bean, pigeon pea, black oat, sorghum and millet, with and without intercropping, with their straws collected at the early grain filling stage. The aqueous extracts of 5% and 10% (w/v) obtained from those straws were placed in plastic boxes (Gerbox-type) containing common bean seeds. The straws were also laid on the substrate surface sown with common bean in plastic pots and installed in the greenhouse for chemical and physical effects evaluation of the cover crops. Considering most of the variables studied, it was not verified any damage by either using of mulch or by applying allelopathic extracts. When used as mulch or when applied as aqueous extracts, residues from the intercropping between sunn hemp and sorghum positively affected the common bean plant, benefiting its initial growth.
  • Authors:
    • Chapagain, T.
    • Riseman, A.
  • Source: American Journal of Plant Sciences
  • Volume: 3
  • Issue: 5
  • Year: 2012
  • Summary: A cultivar trial, including commercial and heirloom cultivars of major cereals and grain legumes was conducted in Vancouver, BC, under low input organic conditions. We assessed 19 wheat (6 commercial and 13 heirloom), 17 barley (8 commercial and 9 heirloom), 5 pea, 5 favabean, 5 kidneybean, 2 lentil, and 2 soyabean cultivars for plant performance metrics, and their potential in a small grain:legume intercropping system. Heirloom wheat cultivars showed notable response in a number of parameters including late maturity, taller plants, greatest number of spikes per m 2, longest spike, highest number of seed per spike, greater seed weight to volume ratio, and resistance to stripe rust compared with commercial cultivars. For the heirloom-type, 6 of 14 wheat cultivars, ( i.e., "Reward", "Glenn", "Cerebs", "Red Bobs", "Sounders" and "Black Bearded") produced yields comparable to the commercial cultivars ( i.e., nearly 5 t/h or higher). Also, heirloom cultivars typically contained higher protein levels most suitable for baking and blending purposes with "Einkorn" displaying the highest level (16.2%). Heirloom and commercial barley cultivars did not differ significantly with respect to plant height, spike length, and seed weight to volume ratio. However, a number of heirloom cultivars (e.g., "Jet", "Dolma", "Andie" and "Himalayan") displayed greater responses on earliness, number of spikes per m 2, grain yield, protein content and seed weight to volume ratio. Pea and lentil yielded lower than the national average under trial conditions. However, heirloom peas "Corgi", "De Grace", "Snowbird", and "Golden" were earlier compared to the commercial cultivar "Reward". All kidney bean cultivars yielded ~3 t/h with the highest yield from "Red Kidney" (3.8 t/h). Fava and soyabean appeared as promising crops as the cultivars produced good growth and yields. Neither lentil ("Crimson" and "Essex") produced satisfactory responses though they had excellent vegetative growth and flowered. Therefore, significant variation was observed including several heirloom cultivars displayed great potential in terms of yield, protein content, and disease resistance and that specific cultivars were better suited for an intercropping system.
  • Authors:
    • Ray, R. V.
    • Imathiu, S. M.
    • Edwards, S. G.
    • Back, M.
    • Hare, M. C.
  • Source: International Journal of Food Microbiology
  • Volume: 156
  • Issue: 2
  • Year: 2012
  • Summary: High levels of Fusarium mycotoxins HT-2 and T-2 have been detected in UK oats since surveys started in 2002. Fusarium langsethiae and the closely related species F. sporotrichioides have previously been associated with the contamination of cereals with type A trichothecenes HT-2 and T-2 in Nordic countries. Preliminary microbiological analysis of UK oat samples with high concentrations of HT-2 and T-2 detected and isolated F. langsethiae and F. poae but not the other type A trichothecene producing species F. sporotrichioides, F. sibiricum and F. armeniacum. Two hundred and forty oat flour samples with a known mycotoxin profile were selected from a previous four year study (2002-2005) to cover the full concentration range from below the limit of quantification (