341. Resistance inducers to the whitefly Bemisia tabaci Biotype B (GENN., 1889) (Hemiptera: Aleyrodidae) in soybeans.; Indutores de resistencia a mosca-branca Bemisia tabaci Biotipo B (GENN., 1889) (Hemiptera: Aleyrodidae) em soja.

• Authors:
  • Ferreira, R. S.
  • Moraes, J. C.
  • Costa, R. R.
• Source: Ciência e Agrotecnologia
• Volume: 33
• Issue: 5
• Year: 2009
• Summary: Studies were conducted to evaluate the effect of the application of inducers on the resistance of 2 soyabean cultivars to the whitefly Bemisia tabaci Biotype B. The seeds of the soyabean cultivars IAC-19 and MONSOY-8001 were previously treated with captan. The following treatments were tested: irrigating the soil around the plants of each pot with 250 ml solution of 1.0% silicic acid (T1); spraying of the plants, to the 'point of dripping', with a solution of 0.3% acibenzolar-S-methyl (T2); spraying of the plants, to the 'point of dripping', with a solution of 0.24% pyraclostrobin+epoxiconazole (T3); and control (T4). The plants were infested with 100 adult whiteflies that were released 8 days after applying the treatments. The number of ova on the abaxial face of each leaf, which was marked for further evaluation of nymphs, tannin and lignin contents and dry weight of the aerial parts and roots. There was no difference for the number of ova and nymphs among the soyabean cultivars. Nevertheless, the average survival rate of B. tabaci was lower on cultivar IAC-19. The application of silicon or acibenzolar-s-methyl induced an increase in lignin content in the soyabean cultivar IAC-19.

342. Dynamics of land use and cover in the watersheds of Guapi-Macacu and Caceribu - RJ.

• Authors:
  • Silva, S. A. da
  • Bastos, E. C.
  • Fadul, M. J. do A.
  • Prado, R. B.
  • Fidalgo, E. C. C.
  • Pedreira, B. da C. C. G.
  • Zainer, N. G.
  • Peluzo, J.
  • do A. Fadul, M. J.
  • da Silva, S. A.
• Source: Boletim de Pesquisa e Desenvolvimento - Embrapa Solos
• Issue: 136
• Year: 2009
• Summary: The basins of rivers Guapi-Macacu Caceribu are located east of the basin of the Bay of Guanabara, in Rio de Janeiro and their watercourses supply water to more than two million people. Their water resources are considered of good quality, but factors such as the removal of riparian vegetation, inappropriate use of land, rectification and siltation of rivers, erosion, urban sprawl, lack of treatment of sewage and the establishment of industries, including the Rio de Janeiro's Complex Petrochemical Rio de Janeiro (COMPERJ) modify the water quality and the storage capacity of these basins. The occurrence of continuous spatial and temporal changes of use and land cover in catchment areas of rivers Guapi-Macacu Caceribu and without the support of adequate funding has caused changes in the structure of the landscape of the region and may bring undesirable consequences for the environment as for the activities of man. Thus, it is necessary to gather information and meet this dynamic process of use and coverage to support the planning of actions in the short, medium and long term, to adequate land use and improving environmental quality in river basins question. Thus, this study aimed to map the spatial-temporal use and land cover in a period previous to the installation of COMPERJ, for the years 1997 and 2007 to record the current scenario and create a starting point for monitoring region's future post-deployment of this enterprise. Mappings were performed for space-time (1997-2007) of use and land coverage using images from Landsat satellite, aerial photographs, survey of secondary data and field work. In addition, this study also aimed to analyze the effect of atmospheric correction on the multitemporal images of the region, using the method of subtraction of the gray levels in the environment ENVI 4.5. The results indicated that this method was not effective in reducing the atmospheric effects of images, and have continued to have a significant influence on the spectral response of the targets. The analysis of the dynamics of land use, the results showed that in 10 years, in terms of absolute values, changes in land cover were occasional and not very responsive. However, individually, changes occurred in some classes of use, among which can be highlighted, for example: The class vegetation in the intermediate stage of regeneration has only reduction in area (12.5 ha), which turned into pasture. Distributed throughout the study region were observed areas of suppression of vegetation in initial stage of regeneration, and noticed an increase in concentration saw Soarinho. These areas began to be occupied by pasture (275 ha), exposed soil (3 ha), water (4.8 ha) and urbanized area of low density (22.7 ha). On the other hand, there was also an increase of vegetation in initial stage of regeneration observed in the vicinity of the Mountain area, north of Macacu and southern Caceribu that was once pasture and agriculture. Was also a small increase in area of mangrove class (127.48 ha) of the APA Guapimirim. The agriculture class, the observed changes relate mainly to the areas of temporary crops. The standing crops due to its sparse distribution on the ground and are made up of small plots and/or located in the shaded, could not be identified clearly in the images. There was so much increased (701.71 ha) and reduction in class agriculture. The areas that have changed their grazing area to agricultural area totaled 891.4 ha and the reverse conversion totaled 178.4 ha. The pasture was a class that suffered the greatest reduction in area (1934.01 ha). However, it should be noted that some areas suffer seasonal changes between the pasture and agriculture, thus changing the use observed in the use class grazing were probably due to soil management and the seasonal farming activities. Moreover, in 2007 it was observed that one of the areas of pasture in 1997 became exposed soil, which is related to increased mining activities in the city of Niteroi, and partly turned into lots for development. The class exposed soil showed a significant increase in area, but that does not qualify on the change of land use, because this class were inserted the areas prepared for farming or grazing reform, which eventually may present as exposed soil. Classes urbanized area and urbanized area of low density experienced expansion in the period between 1997 and 2007, there was intensification of settlements and new areas were added from the conversion of areas previously occupied by pasture and vegetation at an early stage of regeneration. There was an increase in this period of new urban lots, predominantly in the river basin Caceribu, where there is an increasing trend of urbanization due to the installation of the Petrochemical Complex of Rio de Janeiro.Together these classes showed an increase of 504.69 ha, predominantly observed along the roads. The processes of urbanization are occurring mainly in the municipalities of Itaborai and Sao Goncalo. The class water showed an increase in area of 104.11 ha. The greatest change observed with regard to dam the beverage industry Schincariol in Waterfalls Macacu built to retain water. Part of the new areas of water are in areas occupied by mining, especially near the rivers Caceribu. It also observed an increase of small lakes in rural areas have been trained in fish farming and/or leisure activities. With respect to classes of use and coverage included in protected areas, the results indicated that there was more regeneration than removal of natural vegetation between 1997 and 2007. The best-preserved natural vegetation found in areas protected by conservation areas which inhibit the clearing of the remaining areas of Atlantic and help to maintain the quality and quantity of water in river, but does not prevent that they are progressively degraded, a factor that can be accentuated with the installation of COMPERJ.

343. Yield of Cassava Roots Intercropped with Corn and Cowpea in an Organic System

• Authors:
  • Feltran, J. C.
  • De Castro, C. M.
  • De Almeida, D. L.
  • Valle, Teresa L.
  • Duarte Ribeiro, R. De L.
  • Pries Devide, A. C.
• Source: Bragantia
• Volume: 68
• Issue: 1
• Year: 2009
• Summary: Organic systems were evaluated for cassava root production directed to human comsumption in natura, at Seropedica-RJ. Treatments consisted of: cassava ('IAC 576-70') in single cropping and its intercropping with corn ('Eldorado'), cowpea ('Maua') or corn plus cowpea. The organic management was standardized and the experimental area was submitted to artificial irrigation during the period of stay of maize in the system. "Green" (immature) corn ears were harvested at the "point" required for fresh marketing and the shoot placed on the ground. The cowpea was included to function as green manure being Cut at flowering with residues left on the soil Surface. Corn and cowpea were sown between cassava rows, in an alternate design, following the first weeding of the main crop (cassava). The cultivar IAC 576-70 showed suitability with respect to organic management, yielding approximatelu 31 Mg ha(-1) of marketable roots. No significant differences were detected between cassava single cropping and any of the intercropping tested systems. Thus, corn crop has considerable potential for additional income to the growers. Yield of 'Eldorado' corn averaged 18.125 ears ha(-1) correspponding to 5,1 Mg ha-1. Residues coming from cowpea cutting brought about an input close to 12 Mg ha(-1), which meant an expressive contribution in nutrient elements, especially nitrogen (about 44 kg N ha(-1)). The legume crop, in addition, completely covered cassava inter-rows demonstrating its potential for controlling erosion and weeds. The triple intercropping becomes advantageous considering that corn harvesting would justify irrigation and that inclusion of cowpea meant benefitial effects to the system and did not interfere on cassava yield.

344. Use Potential and Structural Quality of Two Soils Under Sugarcane Production in Goianesia, Goias State, Brazil

• Authors:
  • Curi, N.
  • de Oliveira, G. C.
  • Severiano, E. da C.
  • Dias, M. de S.,Jr.
• Source: Revista Brasileira de Ciência do Solo
• Volume: 33
• Issue: 1
• Year: 2009
• Summary: With the expansion of the sugar/alcohol sector, the native vegetation was removed from soils with few limitations as well as with great risks for intensive cultivation and the areas incorporated in the production process. Therefore, the adoption of management systems that maintain the soil structure may be a key for the maintenance of the quality and sustainability of sugarcane production systems. The objective of this study was therefore to evaluate the use potential for sugarcane and structural quality of a Dystrophic Haplic Cambisol (CXvbd) (Inceptisol) and Dystrophic Red-Yellow Latosol (LVAd) (Oxisol), in the county of Goianesia, Goias State. The soils of each area were classified for their use capacity. Disturbed soil samples were collected at depths corresponding to the surface and subsurface diagnostic horizons, for chemical and physical-hydric characterization. Undisturbed samples were collected (from the layers 0-0.05, 0.1-0.15 and 0.3-0.4 m) to determine soil porosity, water retention curves, the least limiting water range and preconsolidation pressure. The evaluation of soils by the land use capacity system indicated that CXvbd belongs to class IVe and LVAd to IIIs. Results of the analysis of the chemical and physical-hydric attributes of the CXvbd indicated that a continuous sugar-cane cultivation, despite the classification as IVe in the use potential system, was due to the adoption of agricultural terraces, aside from the fact that the degrees of soil revolving was lower and of soil cover higher, when sugarcane was harvested green The water availability for plants was highest for CXvbd, which tends to be advantageous for crops. In the study conditions, the LVAd was most susceptible to compaction, which requires limitations of machinery traffic.

345. Timing, location and crop species influence the magnitude of amelioration of aluminum toxicity by magnesium.

• Authors:
  • Rufty, T.
  • Smyth, T. J.
  • Novais, R. F.
  • Correa, T. F. C.
  • Silva, I. R.
  • Silva, E. F.
  • Gebrim, F. O.
  • Nunes, F. N.
• Source: Revista Brasileira de Ciência do Solo
• Volume: 33
• Issue: 1
• Year: 2009
• Summary: The protective effect of cations, especially Ca and Mg, against aluminium (Al) rhizotoxicity was extensively investigated in the last decades. The mechanisms by which the process occurs are however only beginning to be elucidated. Six experiments were carried out to characterize the protective effect of Mg application in relation to timing, location and crop specificity: Experiment 1 - Protective effect of Mg compared to Ca; Experiment 2 - Protective effect of Mg on distinct root classes of 15 soyabean genotypes; Experiment 3 - Effect of timing of Mg supply on the response of soyabean cultivars to Al; Experiment 4 - Investigating whether the Mg protective effect is apoplastic or simplastic using a split-root system; Experiment 5 - Protective effect of Mg supplied in solution or foliar spraying; and Experiment 6 - Protective effect of Mg on Al rhizotoxicity in other crops. It was found that the addition of 50 mmol litre -1 Mg to solutions containing toxic Al increased Al tolerance in 15 soyabean cultivars. This caused soyabean cultivars known as Al-sensitive to behave as if they were tolerant. The protective action of Mg seems to require constant Mg supply in the external medium. Supplying Mg up to 6 h after root exposition to Al was sufficient to maintain normal soyabean root growth, but root growth was not recovered by Mg addition 12 h after Al treatments. Magnesium application to half of the root system not exposed to Al was not sufficient to prevent Al toxicity on the other half exposed to Al without Mg in rooting medium, indicating the existence of an external protection mechanism of Mg. Foliar spraying with Mg also failed to decrease Al toxicity, indicating a possible apoplastic role of Mg. The protective effect of Mg appeared to be soyabean-specific since Mg supply did not substantially improve root elongation in sorghum, wheat, maize, cotton, rice, or snap bean when grown in the presence of toxic Al concentrations.

346. Livestock-crop integration effects on physical attributes of a soil under no-till.; Integracao lavoura e pecuaria e os atributos fisicos de solo manejado sob sistema plantio direto.

• Authors:
  • Fontaneli, R. S.
  • Santos, H. P. dos
  • Spera, S. T.
  • Tomm, G. O.
• Source: Revista Brasileira de Ciência do Solo
• Volume: 33
• Issue: 1
• Year: 2009
• Summary: Soil physical characteristics were evaluated of a typical dystrophic Red Latosol (Typic Haplorthox) located in Passo Fundo, State of Rio Grande do Sul, Brazil, after ten years (1993 to 2003) under mixed production systems. The effects of production systems integrating grain production with winter annual and perennial forages under no-tillage were assessed. Five mixed cropping systems were evaluated: (i) wheat/soyabean, white oat/soyabean, and common vetch ( Vicia sativa)/maize; (ii) wheat/soyabean, white oat/soyabean, and annual forages (black oat ( Avena nuda) + common vetch)/maize; (iii) perennial cool season forages (fescue ( Festuca) + white clover ( Trifolium repens) + red clover ( T. pratense) + birdsfoot trefoil ( Lotus corniculatus)); and (iv) perennial warm season forages (bahiagrass ( Paspalum notatum) + black oat + ryegrass ( L. perenne) + white clover + red clover + birdsfoot trefoil). System V lucerne as hay crop was established in an adjacent area in 1994. Half of the areas under the systems III, IV, and V returned to system I after the summer of 1996 (southern hemisphere). The crops, both summer and winter, were grown under no-till. The treatments were arranged in a randomized complete block design, with four replications. Soil core samples were also collected in a subtropical forest fragment adjacent to the experimental area. The variations in soil bulk density, total porosity, microporosity and macroporosity due to grain production systems with forages were not severe enough to cause soil degradation. The soil bulk density in the production systems with perennial forages was lower and total porosity and macroporosity, in the 0-2 cm layer, higher than in the production systems of grain or of grain with annual forages.

347. Relationships between size of eroded sediments, runoff velocity, surface roughness created by tillage, and size of aggregates in a soil submmited to different managements.

• Authors:
  • da S. Volk, L. B.
  • Cogo, N. P.
  • Volk, L. B. da S.
• Source: Revista Brasileira de Ciência do Solo
• Volume: 33
• Issue: 5
• Year: 2009
• Summary: This work was accomplished with the purpose of establishing quantitative relationships between the D 50 index of the size distribution of the soil-eroded sediments, the runoff velocity, the SR index of the tillage-induced soil surface roughness, and the mean weight diameter (MWD) of the soil aggregates, in a soil submitted to different forms of management. The study was developed in the field, at the Agricultural Experimentation Station of the Federal University of Rio Grande do Sul (EEA/UFRGS), in Eldorado do Sul (RS), Brazil, by applying simulated rainfall on an Ultisol with a sandy clay loam texture in the surface layer and 0.115 m m -1 average slope steepness. This soil had been put into agricultural use by different manners (continuous and discontinued cultivation), with different crop sequences (winter and summer, grass and legume crop species, planted in rows, using no-tillage), for a 7.5 year period (starting at the original condition of native pasture). Seven erosion tests were performed in the study, each one of them at 63.5 mm h -1 rainfall intensity and 1.5 h duration, using the rotating-boom rainfall simulator and 3.5*11.0 m experimental plots. The referred erosion tests were performed in the following soil surface physical conditions: (a) non-mobilized soil, with complete and no cover by crop residues, and (b) soil successively mobilized by the passage of a light disc-harrow (five times, one at a time), with no cover. It was observed that the crop sequences provided values of the MWD index significantly different each other, which reflected in significantly different values of the SR index and, as consequence, of the runoff velocity and the D 50 index, with the sequences with none or less time of discontinued cultivation (in the last period of the research) having produced the best results. In the non-mobilized, completely mulch-covered soil, with a firm and smooth surface, the mulch of crop residues was the dominant factor either in reducing the runoff velocity or in trapping the eventually detached soil particles of larger size, which led to very small values of the D 50 index. In the non-mobilized, uncovered soil, where runoff reached its highest velocities, the size of the eroded sediments was determined by the consolidation of the soil surface and by the values of the MWD index, being the smaller for the greater values of the two last variables mentioned. Yet in the soil successively mobilized by the one at a time passage of a light disc-harrow and bare, with a loose and rough surface, the roughness of the soil surface created by tillage was the dominant factor either in reducing the runoff velocity or in trapping the detached soil particles of larger size, which increased the percentage of eroded sediments

348. Surface liming and zinc availability in a long-term experiment under no-till system.

• Authors:
  • Fonseca, A. F. da
  • Alleoni, L. R. F.
  • Caires, E. F.
  • Churka, S.
• Source: Communications in Soil Science and Plant Analysis
• Volume: 40
• Issue: 17/18
• Year: 2009
• Summary: No-till (NT) system with crop rotation is one of the most effective strategies to improve agricultural sustainability in tropical and subtropical regions. To control soil acidity in NT, lime is broadcast on the surface without incorporation. The increase in soil pH due to surface liming may decrease zinc (Zn) availability and its uptake by crops. A field experiment was performed in Paran State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate Zn bioavailability in a NT system after surface liming and re-liming. Dolomitic lime was surface applied on the main plots in July 1993 at the rates of 0, 2, 4, and 6 Mg ha -1. In June 2000, the main plots were divided in two subplots to study of the effect of surface re-liming at the rates of 0 and 3 Mg ha -1. The cropping sequence was soybean [ Glycine max (L.) Merrill] (2001-2 and 2002-3), wheat ( Triticum aestivum L.) (2003), soybean (2003-4), corn ( Zea mays L.) (2004-5), and soybean (2005-6). Soil samples were collected at the following depths: 0-0.05, 0.05-0.10, and 0.10-0.20 m, 10 years after surface liming and 3 years after surface re-liming. Soil Zn levels were extracted by four extractants: (i) 0.005 mol L -1 diethylenetriaminepentaacetic acid (DTPA)+0.1 mol L -1 triethanolamine (TEA)+0.01 mol L -1 calcium chloride (CaCl 2) solution at pH 7.3 (DTPA-TEA), (ii) 0.1 mol L -1 hydrochloric acid (HCl) solution, (iii) Mehlich 1 solution, and (iv) Mehlich 3 solution. Zinc concentrations in leaves and grains of soybean, wheat, and corn were also determined. Soil pH (0.01 mol L -1 CaCl 2 suspension) varied from 4.4 to 6.1, at the 0- to 0.05-m depth, from 4.2 to 5.3 at the 0.05- to 0.10-m depth, and from 4.2 to 4.8 at the 0.10- to 0.20-m depth, after liming and re-liming. Zinc concentrations evaluated by DTPA-TEA, 0.1 mol L -1 HCl, Mehlich 1, and Mehlich 3 solutions were not changed as a result of lime rate application. Re-liming increased Zn concentrations extracted by 0.1 mol L -1 HCl at 0-0.05 m deep and by DTPA-TEA at 0.05-0.10 m deep. Surface-applied lime promoted a decrease in Zn concentrations of the crops, mainly in grains, because of increased soil pH at the surface layers. Regardless of the liming treatments, levels of Zn were sufficient to soybean, wheat, and corn nutrition under NT.

349. Evaluation of the structure of a eutroferric red nitosol under no-tillage, conventional tillage and forest.; Estrutura de um nitossolo vermelho latossolico eutroferrico sob sistema plantio direto, preparo convencional e floresta.

• Authors:
  • Ralisch, R.
  • Nakashima, P.
  • Gasparetto, N. V. L.
  • Domingos, M. M. M.
  • Tavares Filho, J.
• Source: Revista Brasileira de Ciência do Solo
• Volume: 33
• Issue: 6
• Year: 2009
• Summary: Structural changes caused by management systems to soil can result in compaction and may change crop root development. With the aim to evaluate the effects of the farming systems on the soil structure by qualitative (cultural profile) and quantitative (soil density) methodologies, a field study was carried out in Maringa, state of Parana, Brazil (23degrees29′S, 51degrees59′W). A conventional tillage system with crop succession of corn ( Zea mays L.) and soybean ( Glycine max) and a no-till system with crop rotation of wheat ( Triticum spp.), corn ( Zea mays L.), common bean ( Phaseolus vulgaris), black oats ( Avena strigosa), and soybean ( Glycine max) established for more than 20 years were evaluated. An area under natural forest near the experimental field was evaluated as reference. After the description of the cultural (soil) profile, deformed samples were collected from the homogeneous soil volumes: two samples under forest, two samples in the no-till system and three samples in the conventional system. The physical and morphologic analyses of the soil structures of the layers 0-20 and 20-40 cm showed: (a) the two different tillage system promoted distinct depths of anthropic horizons; (b) the soil structure affected root distribution; (c) soil compaction under conventional system occurred in vertical and horizontal directions (d) soil structure was best under the no-till system; (e) the cultural profile methodology is efficient in soil morphology evaluations.

350. Soil nitrous oxide emissions in long-term cover crops-based rotations under subtropical climate

• Authors:
  • Beber Vieira, F. C.
  • Zanatta, J. A.
  • Piccolo, M. d. C.
  • Costa, F. d. S.
  • Bayer, C.
  • Gomes, J.
  • Six, J.
• Source: Soil & Tillage Research
• Volume: 106
• Issue: 1
• Year: 2009
• Summary: It has been shown that cover crops can enhance soil nitrous oxide (N(2)O) emissions, but the magnitude of increase depends on the quantity and quality of the crop residues. Therefore, this study aimed to evaluate the effect of long-term (19 and 21 years) no-till maize crop rotations including grass [black oat (Avena strigosa Schreb)] and legume cover crops [vetch (Vigna sativa L), cowpea (Vigna unguiculata L. Walp), pigeon pea (Cajanus cajan L. Millsp.) and lablab (Dolichos lablab)] on annual soil N(2)O emissions in a subtropical Acrisol in Southern Brazil. Greater soil N(2)O emissions were observed in the first 45 days after the cover crop residue management in all crop rotations, varying from -20.2 +/- 1.9 to 163.9 +/- 24.3 mu g N m(-2) h(-1). Legume-based crop rotations had the largest cumulative emissions in this period, which were directly related to the quantity of N (r(2) = 0.60, p = 0.13)and inversely related to the lignin:N ratio(r(2) = 0.89,p = 0.01) of the cover crop residues. After this period, the mean fluxes were smaller and were closely related to the total soil N stocks (r(2) = 0.96, p = 0.002). The annual soil N(2)O emission represented 0.39-0.75% of the total N added by the legume cover crops. Management-control led soil variables such as mineral N (NO(3)(-) and NH(4)(+)) and dissolved organic C influenced more the N(2)O fluxes than environmental-related variables as water-filled pore space and air and soil temperature. Consequently, the synchronization between N mineralization and N uptake by plants seems to be the main challenge to reduce N(2)O emissions while maintaining the environmental and agronomic services provided by legume cover crops in agricultural systems. (C) 2009 Elsevier B.V. All rights reserved.