H. Debiasi

Critical limits of soil penetration resistance in a rhodic Eutrudox

Soil penetration resistance is an important indicator of soil physical quality and the critical limit of 2 MPa has been widely used to characterize the soil physical quality, in both no-tillage and conventional systems. The aim of this study was to quantify the influence of different tillage and cropping systems on the soil penetration resistance in a Rhodic Eutrudox. The experiment was carried out in a 5 × 2 factorial, completely randomized block design (tillage systems vs cropping systems), with four replications. The tillage systems consisted of: conventional tillage disk harrow; minimum tillage with annual chiseling; minimum tillage with chiseling every three years; no-tillage for 11 consecutive years; and no-tillage for 24 consecutive years. The factor cropping systems was represented by: crop rotation and crop succession. The soil penetration resistance (SPR) was determined in 20 soil samples per treatment and layer (0.0-0.10; 0.10-0.20 and 0.20-0.30 m) for each soil matric potential: -6, -10, -33, -100, -500 kPa. The SPR was determined at a volumetric soil water content equivalent to the fraction of plant-available water of 0.7. There were no differences of soil penetration resistance between the two cropping systems. Differences in soil penetration resistance among tillage systems were related to the matric potential at which the samples were equilibrated. The critical SPR limit of 2 MPa normally used for conventional tillage should be maintained. However, this value of 2 MPa is inappropriate for the physical quality characterization of Rhodic Eutrudox under no-tillage and/or minimum tillage with chiseling. Regardless of the cropping systems, the critical SPR limit should be raised to 3 MPa for minimum tillage with chiseling and to 3.5 MPa for no-tillage.

Correction of resistance to penetration by pedofunctions and a reference soil water content

The soil penetration resistance is an important indicator of soil compaction and is strongly influenced by soil water content. The objective of this study was to develop mathematical models to normalize soil penetration resistance (SPR), using a reference value of gravimetric soil water content (U). For this purpose, SPR was determined with an impact penetrometer, in an experiment on a Dystroferric Red Latossol (Rhodic Eutrudox), at six levels of soil compaction, induced by mechanical chiseling and additional compaction by the traffic of a harvester (four, eight, 10, and 20 passes); in addition to a control treatment under no-tillage, without chiseling or additional compaction. To broaden the range of U values, SPR was evaluated in different periods. Undisturbed soil cores were sampled to quantify the soil bulk density (BD). Pedotransfer functions were generated correlating the values of U and BD to the SPR values. By these functions, the SPR was adequately corrected for all U and BD data ranges. The method requires only SPR and U as input variables in the models. However, different pedofunctions are needed according to the soil layer evaluated. After adjusting the pedotransfer functions, the differences in the soil compaction levels among the treatments, previously masked by variations of U, became detectable.

Soil penetration resistance in a rhodic eutrudox affected by machinery traffic and soil water content

Soil compaction caused by machinery traffic reduces crop yields. This study aimed to evaluate the effects of intensive traffic, and the soil water content, on the soil penetration resistance (PR) of a Rhodic Eutrudox (Distroferric Red Latosol, Brazilian Classification), managed under no-tillage (NT). The experiment consisted of six treatments: NT with recent chiseling, NT without additional compaction, and NT with additional compaction by 4, 8, 10 and 20 passes of a harvester with a weight of 100 kN (70 kN on the front axle). Undisturbed soil samples were collected at 5.5-10.5 cm and 13.5-18.5 cm depth to quantify the soil bulk density (BD). The PR was assessed in four periods, using an impact penetrometer, inserted in the soil to a depth of 46 cm. The effect of traffic intensities on the PR was small when this variable was assessed with the soil in the plastic consistency. Differences in PR among treatments increased as the soil water content decreased. The increase in the values of PR and BD was higher in the first passes, but the increase in the number of traffics resulted in deeper soil compaction. The machinery traffic effects on PR are better characterized in the friable soil consistency.

Produtividade de soja e milho após coberturas de inverno e descompactação mecânica do solo

The objective of this work was to evaluate the effect of soil winter covers and soil mechanical loosening on soybean and corn yield, in no-tillage system. Two experiments were carried oud in Rio Grande do Sul state, Brazil, in a compacted Argissolo Vermelho (Haplic Acrisol), in the 2005/2006 and 2006/2007 crop seasons. The first experiment was carried out in a complete block design, with a split plot arrangement. The treatments were two theoretical working depths of a driller chisel-type furrow opener (0.06 and 0.12 m, split plot), and three soil winter covers (main plot): fallow, black oat (Avena strigosa), and black oat+common vetch (Vicia sativa). In 2006, the soil cover black oat+common vetch was replaced by oilseed radish (Raphanus sativus). In the second experiment, in a complete block design, the soil was chiseled and treatments consisted of black oat or oilseed radish as winter cover crops. Cover crops reduced soil superficial (0-0,06 m) compaction compared to fallow and, in the 2005/2006-crop season, under low water availability, provided higher soybean and corn yields. In the 2006/2007-crop season, when water availability was higher, the same did not happen. Increasing working depths of the chisel-type furrow opener did not affect soybean or corn yields. Soil chiseling reduced soybean and corn yields in comparison to the continuous no-tillage system.

Resistência mecânica do solo e força de tração em hastes sulcadoras de semeadoras-adubadoras em sistema de integração lavoura-pecuária

A integracao lavoura-pecuaria, realizada mediante a implantacao de pastagens no inverno e a semeadura de milho ou soja no verao, constitui-se numa alternativa para a diversificacao de atividades e ampliacao dos lucros. Animais em pastejo, principalmente em areas agricolas manejadas sob semeadura direta, podem resultar na compactacao adicional do solo, diagnosticada geralmente pelo aumento de resistencia do solo a penetracao (RP). Com o objetivo de avaliar a correlacao entre RP e forca de tracao (FT) medida em hastes sulcadoras de semeadoras-adubadoras, nos anos de 2004 e 2005, foi conduzido um experimento em Sao Miguel das Missoes - RS, em Latossolo Vermelho (0.540 kg kg-1 de argila). Os tratamentos consistiram em quatro intensidades de pastejo, que resultaram em alturas de pastagem de 10; 20; 30 e 40 cm, e de testemunha sem pastejo, organizados em DBC, com tres repeticoes. Avaliou-se a RP, no final do periodo de pastejo, e na semeadura da soja, obteve-se a FT exigida nas hastes sulcadoras de semeadoras-adubadoras. A RP e a FT aumentaram com o incremento na intensidade de pastejo. A correlacao entre essas variaveis foi significativa, comprovando que e possivel avaliar o estado de compactacao do solo por meio da medicao da FT requerida pelas hastes sulcadoras de semeadoras-adubadoras.

Demanda de tração, mobilização de solo na linha de semeadura e rendimento da soja, em plantio direto

The objective of this work was to evaluate the relationship between the draft power (FT) in the fertilizer furrow-opener and the volume of mobilized soil in the sowing line as affected by the amount of residues, tractor traffic and furrow‑opening working depth, and its influence on soybean agronomic performance. Treatments consisted of six residue dosages (DR), two fertilizer furrow‑opener working depths (PT) and two soil traffic conditions - with and without tractor traffic - carried out in a randomized block design, in a split‑split‑plot scheme. The treatments were applied with or without irrigation under no-tillage on a Rhodic Paleudult soil. The different PT and tractor traffic conditions influenced FT significantly. Regardless of the irrigation conditions, DR treatments did not affect soybean grain yield and shoot dry matter weight. In the absence of irrigation, soybean productivity increased by 180 kg ha -1 when PT was changed from 0,064 to 0,10 m, which indicates fertilizer furrow-opener at greater depths as a viable practice to decrease the effects of drought on crop.

Yield of soybean, pasture and wood in integrated crop-livestock-forest system in Northwestern Paraná state, Brazil.

The integrated crop- livestock-forest system can enhance the production of soybeans, meat and wood in regions characterized by sandy soils and warm climate. The aim of this study was to evaluate the yield of soybean, Urochloa ruziziensis grass and eucalyptus in an integrated system during the first four years after the establishment of eucalyptus in the northwestern region of Parana state, Brazil. The experiment was established in October 2009, using soybean (summer) -U. ruziziensis (autumn/winter) succession between single rows of Corymbia maculata (eucalyptus species). The spacing between tree rows and eucalyptus plants in the row were 14 and 4.2 m, respectively. Adjacent plots had the same soybean-U. ruziziensis succession, but without eucalyptus. The spatial variability of soybean grain yields and grass shoot dry matter production was evaluated with and without trees, and the data was analyzed using geostatistics, with the results expressed as spatial variability maps. The tree component did not significantly affect soybean yield in the first two growing seasons. In the 3rd and 4th growing season (2011/12 and 2012/13), the interference of eucalyptus reduced the soybean grain yield by 2.9 and 27.0%, respectively, and the effect was stronger close to the tree rows. In July 2012, the tree component reduced the shoot dry matter productivity of U. ruziziensis by 29.2%. At 19 and 35 months after eucalyptus planting, the cumulative wood volume production was 0.73 and 5.17 m3 ha-1, respectively.

Plant density and mineral nitrogen fertilization influencing yield, yield components and concentration of oil and protein in soybean grains

There are few studies on the interaction between soybean plant density and nitrogen fertilization. This research aimed to assess the effect of mineral nitrogen associated to different plant densities on yield, yield components and oil and protein concentrations of soybean grains. Two experiments were conducted in the 2013/2014 and 2014/2015 growing seasons, with randomized complete block design, in a split plots scheme, with six replications. Four sowing densities (150, 300, 440 and 560 thousand viable seeds∙ha-1) were allocated in the plots, and two nitrogen levels (0 and 45 kg N∙ha-1, applied at V2, using ammonium sulfate) were allocated in the subplots.

Parâmetros solo-máquina em função de doses de resíduos vegetais e profundidades de deposição de adubo em semeadura direta

O trafego continuo e inadequado de maquinas em solos sob semeadura direta tem provocado alteracoes dos atributos fisicos e mecânicos dos solos, influenciando, dessa forma, na produtividade das culturas. O experimento foi conduzido na Estacao Experimental Agronomica da Universidade Federal do Rio Grande do Sul, no municipio de Eldorado do Sul - RS, num Argissolo Vermelho distrofico tipico, com o objetivo de quantificar a forca de tracao e obter informacoes sobre os atributos fisicos do solo, em semeadura direta sobre residuos de aveia-preta e ervilhaca parcialmente decomposta. O delineamento experimental utilizado foi em blocos casualizados, com parcelas subsubdivididas, sendo, nas parcelas principais, doses de residuos da cultura de inverno (0; 1,3; 2,6; 3,2; 3,8 e 5,1 Mg ha-1) de palha de aveia-preta consorciada com ervilhaca, nas subparcelas profundidades de atuacao da haste sulcadora de adubo (0,06 e 0,12 m) e nas subsubparcelas trafegos dos rodados do trator e colhedora. Os atributos fisicos do solo foram afetados pelo trafego dos rodados da maquina. A forca de tracao foi influenciada pela profundidade de atuacao das hastes sulcadoras e o trafego dos rodados.

Changes in a Rhodic Hapludox under no-tillage and urban waste compost in the northwest of Rio Grande do Sul, Brazil

The use of urban waste compost as nutrient source in agriculture has been a subject of investigation in Brazil and elsewhere, although the effects on soil physical and chemical properties and processes are still poorly known. The aim of this study was to evaluate the effect of application of urban waste compost and mineral fertilizer on soil aggregate stability and organic carbon and total nitrogen content of a Rhodic Hapludox under no-tillage in the northwestern region of Rio Grande do Sul, Brazil, in the 2009/2010 and 2010/2011 growing seasons. The experiment was arranged in a 2 × 6 (seasons and fertilization) factorial in a randomized complete block design with four replications. The factor time consisted of two growing seasons (sunflower in 2009/10 and maize in 2010/11) and the factor fertilization of five rates of urban waste compost (0, 25, 50, 75 and 100 m3 ha-1), and mineral fertilizer. Soil samples were collected from the 0.0-0.10 m layer to determine aggregate stability (mean weight and geometric diameter), soil organic carbon (SOC) and total nitrogen (TN). Rates of up to 75 m3 ha-1 of urban waste compost, after two years of application to no-tillage maize and sunflower, improved aggregation compared to mineral fertilization in a Rhodic Hapludox. After the second crop, the SOC and TN contents increased linearly with the levels of urban waste compost.