• Authors:
    • Galizio, R.
    • Moreno, M. V.
    • Dinolfo, M. I.
    • Stenglein, S. A.
    • Salerno, G.
  • Source: PLANT DISEASE
  • Volume: 94
  • Issue: 6
  • Year: 2010
  • Summary: In December 2008, a study of oat (cv. Graciela INTA) seeds from Trenque Lauquen, Buenos Aires, Argentina, was conducted. Seeds were surface sterilized by dipping successively into 70% ethanol for 2 minutes, 5% sodium hypochlorite for 2 minutes, rinsed twice in fresh sterilized distilled water, plated on 2% potato dextrose agar (PDA; pH 6) and incubated at 242°C with 12 h photoperiods. Six isolates morphologically similar to Fusarium spp. were observed after 6 days of incubation. For identification, monosporic isolates were transferred onto 2% PDA and carnation leaf agar (CLA) to grow with the conditions described above. Two isolates produced abundant, white, aerial mycelium and violet-to-dark (with age) pigments in the PDA. On CLA, macroconidia were abundant, slender, almost straight, thin walled and usually 3-5 septate. Microconidia were abundant, usually single celled, oval or club-shaped in chains (less commonly in false heads) on monophialides and polyphialides. Chlamydospores were absent. The fungus was identified as F. proliferatum based on fungal morphology. The pathogenicity of the fungus was tested by spraying 5 healthy inflorescences of oat with a 5 ml suspension (2 * 10 5 conidia/ml). Another 2 healthy inflorescences were sprayed with sterile distilled water. Plants were placed in a growth chamber with a 12 h photoperiod at 222°C and covered with polyethylene bags that were removed after 3 days and plants were moved to a glasshouse. Inoculated inflorescences showed bleaching glumes that sometimes became necrotic with some grains that presented pale brown discoloration and necrotic areas. The fungus was reisolated from glumes and grains of inoculated plants and not from controls. To confirm the morphological diagnosis, the genomic DNA of the isolates was extracted and a PCR reaction with specific primers was chosen. Successful amplifications were confirmed by gel electrophoresis. The size of the DNA fragment was estimated using a 100 bp DNA ladder. The expected size product (585 bp) was obtained, confirming the identification. This is thought to be the first report of F. proliferatum on oat in Argentina.
  • Authors:
    • Fernandez, P. L.
    • Álvarez, C. R.
    • Schindler, V.
    • Taboada, M. A.
  • Source: Geoderma
  • Volume: 159
  • Issue: 1-2
  • Year: 2010
  • Summary: The grazing of crop residues during the winter in integrated crop-livestock systems can either increase soil bulk density (BD) by compaction or decrease BD by swelling, as a function of gravimetric soil water content (GW) during grazing. A field experiment was conducted from 2005 to 2008 to evaluate the BD response to grazing in a no-till silty loam soil (Typic Argiudoll) of the Pampas region of Argentina. Soil BD (core method), GW data and the calculated air volume (AV) were obtained from the 0-50 mm and 50-100 mm layers at different sampling times from ungrazed and grazed treatments. Over most of the study period (2006 through 2008) soil BD showed little impact from grazing, with minimal temporal variation (1.32-1.46 Mg m -3). This stable behavior was ascribed to low rainfall and relatively low GW values at the time when soil was trampled by livestock and routinely trafficked by machinery. Soil BD in the upper (0-50 mm) layer was significantly (p330 g kg -1 in the ungrazed treatment and GW was >240 g kg -1 in the grazed treatments. Grazing accentuated the soil kneading process that promoted air entrapment. Our results suggest in this no-tilled silt loam soil that winter grazing of crop residues caused no deterioration of topsoil porosity in the no-tilled silty loam soil.
  • Authors:
    • Andrasko, K.
    • Bosquet, B.
  • Year: 2010
  • Authors:
    • Pire, E.
    • Boccanelli, S.
    • Lewis, J.
  • Source: CIENCIA E INVESTIGACION AGRARIA
  • Volume: 37
  • Issue: 2
  • Year: 2010
  • Summary: Agriculture has been practised in the Argentine Pampa Region for more than a century. This long history of disturbance has strongly modified the native vegetation of the region. Some original species have disappeared or its area has been remarkably reduced. The objective was to evaluate vegetation changes over time after the abandonment of agriculture practice. Our hypothesis was that over time vegetation in this region will evolve towards a "flechillar" ( Stipa spp. community) similar to the original vegetation. The experiment was conducted at Zavalla (Santa Fe) Argentina (33degrees01′S, 60degrees53′W and 50 m.a.s.l.). Vegetation evolution was studied during 15 years (1982-1997) after abandonment, considering four initial crop situations (i.e. wheat, soybean, pasture and tillage). Periodically, we measured species cover and abundance in 60 subplots. Data was analyzed using multivariate methods. We identified several groups corresponding to two very well defined successional stages. The first group was very small, and showed predominance of annual species; the second group showed a reduction or almost disappearance of annuals and an increase in perennials such as Baccharis salicifolia (Ruiz & Pav.) Pers. and Sorghum halepense (L.) Pers. accompanied by Carduus acanthoides L. Therefore, a secondary succession was developed, with a first stage of annual species dominance followed by long life cycle species. However, even after 15 years there was no reversion of the vegetation to the original community.
  • Authors:
    • Guglielmini, A. C.
    • Abelleyra, D. de
    • Kruk, B. C.
    • Verdu, A. M. C.
    • Mas, M. T.
    • Satorre, E. H.
  • Source: Weed Research
  • Volume: 50
  • Issue: 4
  • Year: 2010
  • Summary: Weed surveys were performed in commercial no-till glyphosate-tolerant soyabean crops in southern Entre Rios province (Mesopotamic Pampas of Argentina) in 2005 and 2007, during the soyabean grain filling to maturity growth stages. The objectives were to describe the weed communities in fields recently introduced to crop production and to analyse the effect of the new cropping patterns on assemblages. The fields surveyed varied in the length of the no-till period (1-11 years), the previous crop and the soil productivity rating. Weed communities were described in terms of composition, constancy, life forms, morphotypes and (only during 2007) frequency. Tragia geraniifolia, Bidens subalternans, Sida spinosa, and Eryngium horridum were species associated with fields with more than 5 years of no-till glyphosate-tolerant crops. These fields had a significantly higher relative abundance of perennials (52% versus 32%) and of dicotyledons (66% versus 39%) than fields with less than 5 years of no-till. Previous crop and soil productivity affected weed community structure. Six species, five of them annuals, were associated with fields that had high yields and maize as the previous crop. In contrast, perennials and dicotyledons had the highest relative abundance when wheat-soyabean double cropping was the previous crop. The results show that changes in cropping systems acted as filters on functional traits, modifying the previous weed community assemblage. The information may be used to develop integrated crop-weed management strategies, leading to a reduction in the assemblage of highly competitive weed communities.
  • Authors:
    • Dourado Neto, D.
    • Righi, C. A.
    • Costa, L. C.
    • Bernardes, M. S.
    • Confalone, A. E.
    • Martin, T. N.
    • Manfron, P. A.
    • Pereira, C. R.
  • Source: Ciência Rural
  • Volume: 40
  • Issue: 5
  • Year: 2010
  • Summary: Predicting crop growth and yield with precision are one of the main concerns of the agricultural science. For these purpose mechanistic models of crop growth have been developed and tested worldwide. The feasibility of an expolinear model for crop growth was evaluated on predicting growth modification on soybean ( Glycine max L. Merrill) of determined and undetermined growth cultivars, submitted to water restrictions imposed on different phenological stages. An experiment was carried out in Azul/Argentina and in Vicosa/Brazil during the growing seasons (1997/1998, 1998/1999 and 2002/2003). The expolinear model was adjusted to the dry-matter data obtained from each treatment. The model showed sensibility of R m (maximum relative growth rate of the culture - g g -1 day -1) to variation in air temperature; of C m (maximum growth rate of the culture - g m -2 day -1) to solar radiation and of T b (lost time-day) to water stress. C m values were higher without water restriction presenting, in both countries, a direct correlation with solar radiation. Without water restrictions, R m values were lower when the average air temperature during the cycle was lower. It was observed that under water stress the culture had a bias to present higher R m values. T b was lower in the irrigated treatments than in those with water deficits. The analysis of the outputs clearly shows the feasibility of the expolinear model to explain the differential growth rates of soybean as a consequence of climatic conditions.
  • Authors:
    • Rosa Becker, A.
    • Camilo Bedano, J.
    • Dominguez, A.
  • Source: Soil & Tillage Research
  • Volume: 110
  • Issue: 1
  • Year: 2010
  • Summary: No-till (NT) has been recognized as a management system of low environmental impact when applied in combination with crop residue mulch and rotations involving cover crops. It has been suggested, however, that, if these conditions are not met, NT may result in physical, chemical and biological soil degradation. This study evaluates the effect of NT on the litter decomposition process and on soil macrofauna communities and how changes in soil physical, chemical, and physicochemical properties affect litter decomposition and soil macrofauna. We hypothesised (1) that macrofaunal abundance, richness and diversity would be lower in NT soils than in natural grasslands; (2) that this would be a consequence of unfavourable physical and chemical soil conditions and high inputs of agrochemicals; and (3) that these changes in macrofauna would influence soil functioning, reducing litter decomposition rate. The study was conducted during winter and spring 2007 on Typic Haplustolls from southern Cordoba, Argentina (32 degrees 41' and 32 degrees 50'S; 63 degrees 58' and 63 degrees 44'W). Macrofauna was sampled twice in NT and in natural grasslands (NA) - as a reference situation - by extracting five soil monoliths of 25 cm x 25 cm x 30 cm at each plot. Soil properties were measured using standard methods. The decomposition rate was determined by the litterbag method, using a 2 mm and a 10 mm size meshes to evaluate litter decomposition mediated by macrofauna. NT greatly reduced richness (from 33 species in NA to 12 species in NT) and abundance (from 1870 ind/m(2) in NA to 475 ind/m(2) in NT) of macroinvertebrates, confirming our first hypothesis. Changes in macrofauna community under NT were mainly explained by high compaction and low organic matter content, confirming our second hypothesis. The reduction in earthworm abundance may also be explained by the influence of the intense use of toxic agrochemicals. No-till increased surface horizon bulk density (from 1.22 to 1.33 g/cm(3)) and decreased organic matter content (from 3.51% to 2.58%) and pH (from 6.74 to 6.01) compared with NA. The litter decomposition rate was lower in NT, confirming our third hypothesis, and it was correlated with low earthworms abundance and activity. We conclude that in our study area the capacity of soils under NT to maintain ecosystem functions would be at risk. (C) 2010 Elsevier B.V. All rights reserved.
  • Authors:
    • Bartosik, R.
  • Source: Julius-Kühn-Archiv
  • Issue: 425
  • Year: 2010
  • Summary: Concerning grain production, South America is divided in two main regions: (1) the Mercosur region (Argentina, Brazil, Uruguay and Paraguay) which produces more than 250 million tonnes of grains and oilseeds, and (2) the Andes Mountain region countries, which are net importers of these products. The main challenges related to grain postharvest that South America is facing are to minimize the quality and quantity losses; improve the food safety; enhance the capability for segregation and traceability of identity preserved (IP) grains; and incorporate technology to maintain the overall efficiency of the postharvest system. Among the critical points affecting the efficiency of the system are the shortage of permanent storage capacity; large storage structures which affects the segregation of IP grains; deficient transportation system (roads and railroads); poor management of integrated pest control system; and unsatisfied demand of formal and informal education in suitable grain postharvest technologies and practices. However, the region remains highly competitive in producing and delivering food for the rest of the world and it has demonstrated high capacity for incorporating cost efficient grain handling technologies. As a result, one of the main changes in the region was the appearance of the silobag system for temporary storage of dry grain and oilseeds. Each silobag can hold approximately 200 tonnes of wheat and with the available handling equipment is quite simple to load and unload. During the 2008 harvest season, more than 33 million tonnes of grain were stored in these plastic bags in Argentina (including corn, soybean, wheat, sunflower, malting barley, canola, cotton seed, rice, lentils, sorghum, beans and even fertilizers). The silobag technology is also being adopted not only in neighbor countries, but also in countries around the world such as the USA, Mexico, South Africa, Australia, Russia and Ukraine, among others.
  • Authors:
    • Catania, C. D.
    • Parera, C. A.
    • Monte, R. F. del
    • Uliarte, E. M.
    • Monte, M. S. A. de del
  • Source: Bulletin de l'OIV
  • Volume: 82
  • Issue: 938/939/940
  • Year: 2009
  • Summary: The aim of this work was to assess the effects of a cover crop, on the vegetative growth and production of grapevine. Three permanent cover crops: Agropyron elongatum (Host) Beauv. (tall wheatgrass), Trifolium pratense L. (red clover), the association Secale cereale L. - Bromus catharticus Vahl (cereal rye-rescuegrass) and two annual species: Sorghum sudanense (Piper) Stapf (Sudangrass), X Triticosecale Wittmack (triticosecale) were compared, with respect to no till soil management by herbicides application. The study was developed in a cv. Malbec vineyard with surface irrigation and in a vertical shoot positioning trellis system, located in Mendoza, Argentina. Parameters related to vegetative expression, grape production and its oenological potential were determined. Permanent covers of red clover, tall wheatgrass and the mixture cereal rye-rescuegrass restricted grapevine vigour compared to open soil (control), diminishing shoot growth, size of leaves and pruning weight. A lower yield production was also observed, with smaller clusters and a reduction of clusters per vine; with greater amounts of total anthocyanins and polyphenols. Permanent cover crops decreased titratable acidity and free amino nitrogen in the must; which slightly delayed alcoholic fermentation, although without stuck fermentation. In the wine tasting evaluation, wines coming from the three treatments with permanent cover crops were preferred by tasters and they appear with greater varietals authenticity. The introduction of a permanent cover crop reduced vegetative growth and yields of the grapevine, modifying the balance vigour/production of the vineyard, and therefore the composition of grapes and wine, without the need to conduct specific cultural operations.
  • Authors:
    • Zorza, E.
    • Perez, L.
    • Perez, M.
    • Rainero, H.
    • Rodriguez, N.
    • Leguizamon, E.
    • Fernandez-Quintanilla, C.
  • Source: Weed Research
  • Volume: 49
  • Issue: 1
  • Year: 2009
  • Summary: Field trials were established in various growing seasons in four experimental sites with soyabeans or maize grown under no tillage systems. Seeds of Digitaria sanguinalis, Eleusine indica, Sorghum halepense, Setaria geniculata, Echinochloa colonum and Urochloa platyphylla were incorporated in surface soil, under the crop residues of the previous season, each autumn. Regular records of seedling emergence during the following spring and summer were used to model the pattern of each species as a function of the thermal time in the 2 cm upper layer of the soil profile. A Weibull function closely described ( r2=0.73-0.93) the relationship between thermal time and seedling emergence for all species in each site and year. The coefficient of determination for the model verification ranged from 0.71 to 0.98. Species may be grouped into three emergence time-span groups. Eleusine indica, U. platyphylla and E. colonum had a long-lasting emergence, requiring 940-1660 ddegreesC (growing day degrees) to complete this process. Digitaria sanguinalis and S. halepense had an intermediate emergence time-span, completing this process in 540-1090 ddegreesC. Setaria geniculata exhibited the shortest emergence time-span (290-660 ddegreesC required for full emergence). Different hypotheses were tested in order to explain species model parameter differences in different sites and to establish the basis for more refined models with improved prediction capabilities.