• Authors:
    • Lopes, S. A.
    • Bassanezi, R. B.
    • Gasparoto, M. C. G.
    • Coletta-Filho, H. D.
    • Amorim, L.
    • Lourenço, S. A.
  • Source: Plant Pathology
  • Volume: 61
  • Issue: 4
  • Year: 2012
  • Summary: The objectives of this work were (i) to determine the influence of temperature on infection of citrus by 'Candidatus Liberibacter asiaticus' and 'Candidatus Liberibacter americanus', the two bacterial species associated with citrus huanglongbing (HLB) in Brazil, and (ii) to determine the influence of temperature on citrus colonization by 'Ca. L. asiaticus', which has taken over from 'Ca. L. americanus' as the predominant species in Brazil since 2008. Two experiments were carried out with graft-inoculated Valencia oranges on Rangpur lime rootstocks. Immediately after inoculation the plants were maintained for 423 days in growth chambers under the following night/day temperature conditions: 17/22, 22/27 or 27/32°C, with a dark/light photoperiod of 8/16 h. Infection and colonization of plants were determined using quantitative PCR (qPCR). ' Candidatus Liberibacter americanus' did not infect the plants maintained at 27/32°C; however, infection by 'Ca. L. asiaticus' occurred at all studied temperatures. Two months after inoculation, 'Ca. L. asiaticus' was distributed throughout the inoculated plants, with mean Ct values in the range of 30-31 for leaves and 25-28 for roots. Over time, ' Ca. L. asiaticus' reached the highest titres in mature leaves (mean Ct value=26.7) of citrus plants maintained at 22/27°C. 'Candidatus Liberibacter asiaticus' colonization of citrus plants was negatively affected by the daily temperature regime of 27/32°C (mean Ct value in mature leaves=33.6).
  • Authors:
    • Hau, B.
    • Lourenco, S. A.
    • Stuchi, E. S.
    • Goncalves, F. P.
    • Amorim, L.
  • Source: Plant Pathology
  • Volume: 91
  • Issue: 11
  • Year: 2012
  • Summary: Citrus Variegated Chlorosis (CVC) is currently present in approximately 40% of citrus plants in Brazil and causes an annual loss of around 120 million US dollars to the Brazilian citrus industry. Despite the fact that CVC has been present in Brazil for over 20 years, a relationship between disease intensity and yield loss has not been established. In order to achieve this, an experiment was carried out in a randomized block design in a 3*2 factorial scheme with 10-year-old Natal sweet orange. The following treatments were applied: irrigation with 0, 50 or 100% of the evapotranspiration of the crop, combined with natural infection or artificial inoculation with Xylella fastidiosa, the causal agent of CVC. The experiment was evaluated during three seasons. A negative exponential model was fitted to the relationships between yield versus CVC severity and yield versus Area Under Disease Progress Curve (AUDPC). In addition, the relationship between yield versus CVC severity and canopy volume was fitted by a multivariate exponential model. The use of the AUDPC variable showed practical limitations when compared with the variable CVC severity. The parameter values in the relationship of yield-CVC severity were similar for all treatments unlike in the multivariate model. Consequently, the yield-CVC intensity relationship (with 432 data points) could be described by one single model: y=114.07 exp(-0.017 x), where y is yield (symptomless fruit weight in kg) and x is disease severity ( R2=0.45; P
  • Authors:
    • Silva, J. A. A.
    • Modesto, R. T.
    • Miguel, F. B.
    • Grizotto, R. K.
    • Vieira Jr., J. B.
  • Source: Revista Brasileira de Engenharia Agrícola e Ambiental
  • Volume: 16
  • Issue: 7
  • Year: 2012
  • Summary: The effect of a technological package implemented in a Valencia orange orchard was studied and compared with the conventional system, based on the production and quality of the fruits harvested. The technologies implemented included the densification, fertilization during implantation and training, phytosanitary treatment, weed management, irrigation and pruning. The results for the fruits from the first harvest showed that the Technified System and Irrigation (TS+I) resulted in significant increase in crop yield. This increase was higher in orchards with a higher density of 727 plants ha -1 (5.5*2.5 m spacing) or 667 plants ha -1 (6.0*2.5 m spacing). In general, irrigation concomitant with TS resulted in larger sized fruits and consequently less fruit per standard sized box, and lower soluble solids and titrable acidity. There was no effect on juice yield with the production system or spacing. It is concluded that, in this first evaluation, orchard management technologies concomitant with irrigation (TS+I) is interesting because promoted an increase in crop yield compared to conventional systems.
  • Authors:
    • Sil, A. C. da
    • Azevedo, F. A. de
    • Correa, F. E.
    • Kupper, K. C.
  • Source: Scientia Horticulturae
  • Volume: 134
  • Year: 2012
  • Summary: The objective of this research was to study the viability of Bacillus subtilis (ACB-69) to control the casual agent in postbloom fruit drop, Colletotrichum acutatum under field conditions. During the 2007/2008 crop season, B. subtilis was tested in 5% (5*10 8 cfu ml -1) and 10% (1*10 9 cfu ml -1) concentrations on 'Pera' sweet orange ( Citrus sinensis (L.) Osbeck) plants grafted on Rangpur lime ( Citrus limonia Osb.), in Botucatu, Sao Paulo, Brazil. The same treatments were repeated in the 2008/2009 crop season with and without adding a carbon source (molasses 5%) to 'Valencia' sweet orange plants grafted on Rangpur lime. Additional experiment was conducted to determine the most appropriate flower growth stage to apply the biocontrol agent. The biological products were applied with an air assisted sprayer in all experiments with the intention of evaluating the practicality of this type of sprayer. A weekly application of B. subtilis (5*10 8 cfu ml -1) reduced the quantity of symptomatic flowers by 47% while the chemical treatment only had an 18% reduction. On the other hand, B. subtilis (10% or 1*10 9 cfu ml -1) applied weekly or applied one week before to the "green bud bloom" stage (like a preventive control) provided a greater average number of effective fruits (ANEF). The addition of a carbon source at the time of application, did not favor the antagonistic activity of bacteria. In controlling postbloom fruit drop, the best time to apply B. subtilis was observed in the open flower stage when the percentage of symptomatic flowers was evaluated. However, when the bacterium was applied in all flowering stages there was a greater average number of effective fruits. The use of air assisted sprayer helped implement the antagonistic on a commercial scale.
  • Authors:
    • Assis, C. P.
    • Jucksch, I.
    • Mendonça, E. S.
    • Neves, J. C. L.
    • Silva, L. H. M.
    • Wendling, B.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 43
  • Issue: 5
  • Year: 2012
  • Summary: The objective of this study was to evaluate changes in distribution and quality of organic matter in light and heavy fractions of a medium-texture Red Latosol under different uses and management practices in Capinopolis, Brazil. Soil samples were collected from different layers in the profile (0-5, 5-10, and 10-20 cm). The following treatments were evaluated: NTs, no till (no tillage) for 4 years with maize (silage)/soybean in succession; NTg, no till for 4 years with maize/maize/maize/soybean in succession; NTtf, no till for 3 years with tifton (hay) and soybeans in the last year; CS, about 30 years with conventional cultivation system (maize/soybean) with only soybean in the past 4 years; and NF, native forest. The heavy fraction contributed 75-98% of total carbon and 94-99% of total nitrogen, indicating that most carbon and nitrogen in the soil are associated with the mineral fraction, which is fundamental for the maintenance of their stocks. Tifton grass in no tillage was efficient in increasing the amounts of light fraction (free and occluded). Increases of occluded light fraction in no-till systems were greater than in conventional cultivation system. The light fraction was shown to be sensitive to soil cultivation and can be considered indicative of soil degradation. Light-fraction analysis by Fourier transform infrared spectroscopy (FTIR) allowed the study of changes in the chemical structure of these fractions under different uses and management practices. Occluded light fraction was shown to be more recalcitrant and condensed than the free light fraction. The surface layer in the conventional cultivation system has a more aromatic and condensed free light fraction than in no-tillage system. In general, the upper layers were less aromatic than the deepest ones.
  • Authors:
    • Briedis, C.
    • Sa, J. C. de M.
    • Caires, E. F.
    • Navarro, J. de F.
    • Inagaki, T. M.
    • Boer, A.
    • Ferreira, A. de O.
    • Quadros Neto, C.
    • Canalli, L. B.
    • Santos, J. B. dos
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 1
  • Year: 2012
  • Summary: In a no-till system (NTS) on naturally acidic soils, surface liming is essential to neutralize soil acidity and increases crop productivity. As a result, the soil organic matter (SOM) pools of the soil surface layers may change, reflecting increased C inputs by crop residues. The objective of this study was to quantify changes in SOM pools and the rate of C sequestration that occur in response to surface liming in a long-term NTS experiment. The experiment was conducted in an Oxisol in southern Brazil. The treatments consisted of the application of 0 or 6 Mg ha -1 of dolomitic lime on the soil surface in 1993 and a reapplication of 0 or 3 Mg ha -1 of dolomitic lime in 2000 to plots with or without the previous lime application. Liming caused total organic C (TOC) accumulation, especially in the 0- to 2.5-cm layer. The amount of TOC stored in the 20-cm layer was 49.9, 52.9, 52.7, and 57.5 Mg ha -1 in the control, 6+0, 0+3, and 6+3 Mg ha -1 treatments, respectively. The levels of particulate organic C (POC) and mineral-associated organic C (MAOC) in the SOM were also enhanced by liming. The increase in POC was directly related ( R2=0.99, P=0.002) to the accumulation of C from crop residues, which was greater in the plots receiving lime treatment. There were positive correlations between TOC and C extractable with hot water, total polysaccharides, and labile polysaccharides. The correlation analysis also demonstrated that TOC was more tightly correlated with POC than with MAOC, indicating a greater influence of the labile fraction on the increase in TOC with surface liming.
  • Authors:
    • Santos,J. B. dos
    • Canalli,L. B.
    • Ferreira,A. de O.
    • Quadros Neto,C.
    • Boer,A.
    • Inagaki,T. M.
    • Navarro,J. de F.
    • Caires,E. F.
    • Sa,J. C. de M.
    • Briedis,C.
  • Source: Geoderma
  • Volume: 170
  • Year: 2012
  • Summary: The stabilisation of soil organic matter (SOM) is the result of the simultaneous action of three mechanisms: chemical stabilisation, biochemical stabilisation and physical protection. The objectives of this study were (i) to evaluate carbon-protection mechanisms in different SOM pools in soil aggregates and (ii) to identify the association of Ca 2+ with total organic carbon (TOC) under the influence of surface liming in a medium-textured Oxisol in a long-term experiment under no-till system (NTS) in southern Brazil (25 degrees 10′S, 50 degrees 05′W). The treatments consisted of application of zero or 6 tons ha -1 of dolomitic lime on the soil surface in 1993 and a reapplication of zero or 3 tons ha -1 of dolomitic lime in 2000 to plots with or without previous lime application. Soil samples collected at depths of 0-2.5, 2.5-5, 5-10 and 10-20 cm were separated into seven aggregate classes. In each of these classes, TOC, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) were analysed. The 8-19 mm sized aggregates from the 0-2.5 cm layer were assessed by energy-dispersive X-ray spectroscopy (EDS) for the elemental analysis of carbon (C) and calcium (Ca). The liming caused an accumulation of TOC in the aggregates, mainly at a depth of 0-2.5 cm. The aggregates from soils treated with lime had a higher mean weight diameter (MWD) that resulted in the accumulation of TOC, especially in the 8-19 mm aggregate class, that was linear and closely related with C input (R 2=0.99). The proportion of large aggregates in the treatments with lime was closely correlated with the TOC content of the whole sample. The largest dose of lime (9 tons ha -1) resulted in higher TOC, POC and MAOC values, mainly in the 8-19 mm aggregate class. The elemental analyses for C and Ca revealed similar spectra between them for the surface-liming treatments in the clay fraction found in the centres of the 8-19 mm aggregates. The surface application of lime to NT fields provided greater stability and protection of the intra-aggregate C, presumably due to Ca 2+ acting as a cationic bridge between OC and the kaolinite in the clay fraction.
  • Authors:
    • Caires, E. F.
    • Joris, H. A. W.
    • Churka, S.
    • Zardo Filho, R.
  • Source: Brazilian Archives of Biology and Technology
  • Volume: 55
  • Issue: 2
  • Year: 2012
  • Summary: The aim of this work was to study the effects of organic and mineral fertilizers at sowing (without fertilizers, organic poultry litter fertilizer on the surface and mineral NK+reactive natural phosphate from Arad and NK+triple superphosphate in the furrow) and topdressing (without fertilizers, organic poultry litter fertilization and urea) on chemical attributes of a no-till Oxisol and nutrition and yield of maize landrace ( Zea mays L.), Carioca variety in a field experiment. Results revealed that P content (Mehlich 1 and resin) was increased in the soil surface layer with organic poultry litter fertilizer on the surface at sowing. Mineral fertilizer in the sowing furrow could be replaced by organic fertilizer with poultry litter on the surface, but topdressing fertilization with urea resulted better N nutrition for the plants and higher grains yield than the organic poultry litter fertilization.
  • Authors:
    • Avares Filho, J. T.
    • Feltran, C. T. M.
    • Oliveira, J. F. de
    • Almeida, E. de
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 36
  • Issue: 1
  • Year: 2012
  • Summary: Soil penetration resistance is an important property that affects root growth and elongation and water movement in the soil. Since no-till systems tend to increase organic matter in the soil, the purpose of this study was to evaluate the efficiency with which soil penetration resistance is estimated using a proposed model based on moisture content, density and organic matter content in an Oxisol containing 665, 221 and 114 g kg -1 of clay, silt and sand respectively under annual no-till cropping, located in Londrina, Parana State, Brazil. Penetration resistance was evaluated at random locations continually from May 2008 to February 2011, using an impact penetrometer to obtain a total of 960 replications. For the measurements, soil was sampled at depths of 0 to 20 cm to determine gravimetric moisture (G), bulk density (D) and organic matter content (M). The penetration resistance curve (PR) was adjusted using two non-linear models (PR= a D b G c and PR′= a D b G c M d), where a, b, c and d are coefficients of the adjusted model. It was found that the model that included M was the most efficient for estimating PR, explaining 91% of PR variability, compared to 82% of the other model.
  • Authors:
    • de Oliveira, F. de A.
    • da S. Soares, L. C.
    • Soares, L. C. da S.
    • Freire, A. G.
    • Oliveira, F. R. A. de
    • Medeiros,J . F. de
    • Oliveira, F. de A. de
    • de Medeiros, J. F.
    • de Oliveira, F. R. A.
  • Source: Revista Ciencia Agronomica
  • Volume: 43
  • Issue: 2
  • Year: 2012
  • Summary: This study was conducted to evaluate the effect of different salinity levels of irrigation water and seed treated with growth regulator on the yield of cotton. It was used an entirely statistical randomized design, in a factorial scheme 5*2, with four replications. The treatments resulted from the combination of four salinity levels of irrigation water (S 1-0.5; S 2-2.0; S 3-3.5; S 4-5.0 and S 5-6.5 dS m -1) in treated and untreated seeds with growth regulator. The variables were: production of cotton, seed and fiber, 100 seed weight and percentage of fiber. There was not interaction between salinity levels and seed treated. The parameters of cotton production are reduced with the use of water salinity from 3.5 dS m -1, independent of seed treated or not with growth regulators. Agronomic traits 100 seed weight, percentage of fiber and seed cotton production are not influenced by mepiquat chloride. The seed treatment with growth regulator do not affects the adverse effect of salinity.