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Pontal do Paraná, Brazil

The least limiting water range (LLWR) is considered a modern indicator of soil physical quality for plant growth. The aim of this study was to determine the LLWR for assessing the soil physical quality of a dystroferric Red Latosol (Oxisol) under no-tillage in a crop-livestock integration system. In the crop-livestock integration system of the study area, soybean was planted in the summer and oat (Avena strigosa Schreb) plus ryegrass (Lolium multiflorum Lam) in the winter with different pasture heights during grazing: 7, 14, 21, and 28 cm, and an ungrazed control. Undisturbed soils samples were taken from the layers 0-7.5 and 7.5-15 cm, in which the soil bulk density (Bd), soil water retention and soil resistance to penetration curves were determined, to then calculate the LLWR. The critical soil bulk density (Bdc) was determined for LLWR=0. Regardless of the treatments, it was found that an increase of the soil bulk density requires an increase of soil water contents to maintain soil penetration resistance below 2.5 MPa and a decrease in soil water to ensure adequate soil aeration, mainly in the 0-7.5 cm layer. In the treatments with grazing heights of 21 and 28 cm, the magnitude of LLWR was greater than in the control, suggesting that crop-livestock integration creates a positive soil physical environment, provided that an appropriate stocking is maintained to prevent overgrazing. In the 7 cm treatment, the soil physical degradation was very high in the 0-7.5 cm layer, and certainly predisposes the crops to stress resistance to soil drying and to reduced aeration under prolonged conditions of high soil moisture. A progressive reduction in the proportion of samples with greater bulk density values than the critical density of the 7 cm treatment toward the control was verified, indicating that the treatment effect of excessive animal trampling resulted in a loss of soil physical quality in the 0-7.5 cm soil layer. The grazing height of oat and ryegrass pasture should be maintained above 21 cm to ensure adequate physical soil quality in the 0-7.5 cm soil layer. Source

The objective of this work was to evaluate the alterations in carbon and nitrogen mineralization due to different soil tillage systems and groundcover species for intercropped orange trees. The experiment was established in an Ultisol soil (Typic Paleudults) originated from Caiuá sandstone in northwestern of the state of Paraná, Brazil, in an area previously cultivated with pasture (Brachiaria humidicola). Two soil tillage systems were evaluated: conventional tillage (CT) in the entire area and strip tillage (ST) with a 2-m width, each with different groundcover vegetation management systems. The citrus cultivar utilized was the 'Pera' orange (Citrus sinensis) grafted onto a 'Rangpur' lime rootstock. The soil samples were collected at a 0-15-cm depth after five years of experiment development. Samples were collected from under the tree canopy and from the inter-row space after the following treatments: (1) CT and annual cover crop with the leguminous Calopogonium mucunoides; (2) CT and perennial cover crop with the leguminous peanut Arachis pintoi; (3) CT and evergreen cover crop with Bahiagrass Paspalum notatum; (4) CT and cover crop with spontaneous B. humidicola grass vegetation; and (5) ST and maintenance of the remaining grass (pasture) of B. humidicola. The soil tillage systems and different groundcover vegetation influenced the C and N mineralization, both under the tree canopy and in the inter-row space. The cultivation of B. humidicola under strip tillage provided higher potential mineralization than the other treatments in the inter-row space. Strip tillage increased the C and N mineralization compared to conventional tillage. The grass cultivation increased the C and N mineralization when compared to the others treatments cultivated in the inter-row space. Source

Araujo-Junior C.F.,Instituto Agronomico do Parana IAPAR | Dias Junior M.S.,Brazilian National Council for Scientific and Technological Development | Guimaraes P.T.G.,Federal University of Lavras | Alcantara E.N.,Federal University of Lavras
Revista Brasileira de Ciencia do Solo | Year: 2011

Different weed managements in coffee have led to structural changes, affecting the soil physical quality. Therefore, information on the load bearing capacity of the soil under different weed managements is essential to establish a sustainable soil management under coffee. The objectives of this study were to: (a) assess the influence of different weed managements over three decades on the load bearing capacity of a Dystroferric Red Latosol (LVdf) cultivated with coffee on the Epamig Farm in São Sebastião do Paraíso, Minas Gerais State (Latitude de 20 ° 55 ' 00 S and Longitude 47 ° 07 ' 10 W); (b) determine the maximum stress (σmax) exerted by a tractor; (c) establish the critical water content (θcrítica) for tractor traffic. The following weed managements were assessed: no weeding (SCAP); hand weeding (CAPM); post-emergence herbicide (HPOS); mowing (ROÇA); rotary tiller (ENRT); tandem disk harrow (GRAD) and pre-emergence herbicide (HPRE). In each management system 15 undisturbed soil samples were collected randomly in the coffee inter-rows in the layers 0-3, 10-13 and 25-28 cm, totaling 315 soil samples. Additionally, 15 samples per layer were collected in a native forest (MATA). The equipment used in coffee management was coupled to a Valmet® model 68 tractor for coffee. To determine θcrítica for tractor traffic, only the stress was considered that did not exceed the internal strength of the soil expressed as precompression stress. The undisturbed soil samples were used to determine precompression stress (σp) at different volumetric water contents (θ) and then bulk density (Bd). Disturbed samples were used to analyze particle size distribution, organic carbon (OC) and total oxides. Load bearing capacity (LBC) between precompression stress and volumetric water content was calculated (σp = 10(a+bθ)) to assess the possible effects of weed management systems on soil structure. The maximum stress caused by the Valmet® tractor (inflation pressure of the front tires 6-16 of 172 kPa) was 220 kPa. The lowest critical water content was 0.27 cm3 cm-3 for the Dystroferric Red Latosol under no weeding in the 0-3 cm layer and the highest 0.48 cm3 cm-3 for the soil managed with pre-emergence herbicide in the 0-3 cm layer. The weed management with disk harrow and pre-emergence herbicide led to crusting on the soil surface and increased bulk density and precompression stress. The load bearing capacity of the soil under native forest was lower in the three layers studied compared to the soil under coffee and different weed managements. The different weed managements used in the interrows did not influence soil bulk density and organic carbon content of Latossol, in the 25-28 cm layer, compared to the soil under native forest (MATA). Source

Borsato L.C.,Instituto Agronomico do Parana IAPAR | di Piero R.M.,Federal University of Santa Catarina | Stadnik M.J.,Federal University of Santa Catarina
Tropical Plant Pathology | Year: 2010

The aim of this work was to evaluate the potential of algal polysaccharide ulvan to induce resistance to rust and to study defense mechanisms triggered by it in bean cultivars showing different levels of resistance. Bean cultivars of carioca group, i.e., BR IPA - 11 Brigida (resistant), Perola (moderately susceptible) and IPR Juriti (susceptible), were sprayed with ulvan (10 mg/ mL) or distilled water (control) at 6 and 3 days before inoculation with Uromyces appendiculatus. Ulvan reduced the diameter of pustules on the three cultivars and led to an increase in the activity of glucanases only in cv. Perola, 48 h after inoculation. The polysaccharide did not inhibit the germination of the fungus in leaf discs and did not alter the activity of peroxidases. Comparing the cultivars, Brigida exhibited a significantly lower number and diameter of pustules, but allowed the highest germination of uredospores on the leaf surface. The activities of peroxidases and glucanases were lower in this cultivar compared to the susceptible one (Juriti). Based on the results, we discuss the role of some resistance mechanisms in both basal and ulvan-induced resistance of bean towards the rust fungus. Source

Minuzzi R.B.,Federal University of Santa Catarina | Caramori P.H.,Instituto Agronomico do Parana IAPAR | Borrozino E.,Instituto Agronomico do Parana IAPAR
Bragantia | Year: 2011

This study aimed to analyze the variability of seasonal and annual maximum and minimum air temperatures in the State of Paraná, southern Brazil. The regression analysis and Kendall test were used to test the trend of mean maximum and minimum temperatures, number of days with records of temperature below 3 °C, extreme events and absolute daily maximum and minimum temperatures on seasonal scales (summer, autumn, winter and spring) and annual. The points of discontinuity obtained by the Standard Normal Homogeneity Test showed more significant results for the annual maximum temperature in the autumn. For this meteorological variable points were obtained predominantly in the early 2000s. The annual maximum temperature and mainly minimum temperature at all time scales tended to increase. This increase was relatively larger in the minimum temperature, which suggests a decrease in the thermal amplitude in Paraná. The values of the extreme daily minimum temperature are being higher, but less frequent. On the other hand, the maximum temperatures have been more intense and frequent, especially in spring. Source

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