Silvio Tulio Spera

Efeitos de sistemas de produção de grãos envolvendo pastagens sob plantio direto nos atributos físicos de solo e na produtividade

Ley forming modifier soil structure, which, in turn, effects soil physical characteristics in the upper layer. The objective of this study was to evaluate soil physical attributes and grain yield in a typical dystrophic Red Latosol (Typic Haplorthox) located in Passo Fundo county (RS), Brazil, after eight years of mixed production cultivation (1993 to 2000). The effects of production systems integrating grain production with winter annual and perennial pastures under no-tillage were assessed. Four mixed production systems were evaluated: system I (wheat/soybean, white oat/soybean, and common vetch/corn); system II (wheat/soybean, white oat/soybean, and grazed black oat + grazed common vetch/corn); system III [perennial cool season pastures (fescue + white clover + red clover + birdsfoot trefoil)]; and system IV [perennial warm season pastures (bahiagrass + black oat + rye grass + white clover + red clover + birdsfoot trefoil)]. System V (alfalfa as hay crop) was established in an adjacent area in 1994. The areas under systems III, IV, and V returned to system I after the 1996 summer. The treatments were arranged in a randomized complete block design, with four replicates. As a control, physical soil parameter were evaluated in samples of a subtropical forest fragment adjacent to the experiment. Soil bulk density values were lower in the top layer (0-5 cm) than in the deeper layer (10-15 cm), while the reverse was observed for the total porosity and macroporosity. Systems I, II, III, and IV showed higher bulk density values and lower total porosity and macroporosity values in the surface layer (0-5 cm). System V and subtropical forest presented low bulk density and high total porosity and macroporosity values compared to the other treatments. It was observed no differences between physical attributes of integrated and non-integrated crop and livestock systems. No significant correlation was verified between crop yields and physical soil attributes, with exception of the soil macroporosity under soybean in the 0-5 cm layer.

Efeito de pastagens de inverno e de verão em características físicas de solo sob plantio direto

Soil physical characteristics were evaluated, after seven years (1995 to 2001), on a typical Dystrophic Red Latosol located in Coxilha, State of Rio Grande do Sul, Brazil. Six systems integrating crop production with livestock and a subtropical forest were evaluated. Both winter and summer crops were seeded under no-tillage. Cropping systems and soil of different sampling depths were compared using the contrast procedure. In the I and II sistems and in the forest, the soil density and the resistance to penetration increased in the top layer (0-0,05m) concerning the deeper layer (0,10-0,15m). In the II system, total porosity and microporosity decreased in the surface. In the subtropical forest, the some was observed in relation to total porosity and microporosity. The forest showed decrease on soil density and resistance to penetration, compared to most crop systems studied, from 0-0,05m layer to 0,100,15m layer. Soil degradation in the systems could not be considered severe.

Características físicas de um latossolo vermelho-escuro no Cerrado de Planaltina, DF, submetido à ação do fogo

Os principais efeitos do fogo como manejo de solo estao relacionados a alteracoes biologicas e quimicas do solo. A queima pode ainda alterar a umidade do solo em razao de mudancas na taxa de infiltracao, na taxa de transpiracao, na porosidade e na repelencia do solo a agua. O objetivo deste trabalho foi avaliar as caracteristicas fisicas de um Latossolo Vermelho-Escuro muito argiloso, plano, fase campo cerrado, submetido a acao do fogo, apos ser utilizado durante 20 anos em pastagem nativa sem queima. Uma area de 1,25 ha foi submetida a acao bienal do fogo, e uma area adjacente, do mesmo tamanho, foi mantida protegida da acao do fogo. Apos seis anos, nao houve variacoes marcantes nas caracteristicas fisicas do solo induzidas pelo fogo, exceto no aumento da umidade do solo nas parcelas nao queimadas. Nas parcelas onde se aplicou o fogo, observou-se tendencia para o aumento da microporosidade, que pode ser atribuida a compactacao promovida pelo impacto das gotas de chuva no solo desnudado pelo fogo. Conclui-se, entretanto, que a queima bienal nao foi suficiente para provocar degradacao no periodo estudado.

Rendimento de grãos de soja em função de diferentes sistemas de manejo de solo e de rotação de culturas

O objetivo do presente trabalho foi avaliar sistemas de manejo de solo e de rotacao de culturas sobre o rendimento de graos e componentes do rendimento de soja durante seis anos. Foram comparados quatro sistemas de manejo de solo - 1) plantio direto, 2) cultivo minimo, no inverno e semeadura direta, no verao, 3) preparo convencional de solo com arado de discos, no inverno e semeadura direta, no verao e 4) preparo convencional de solo com arado de aivecas, no inverno e semeadura direta, no verao - e tres sistemas de rotacao de culturas: sistema I (trigo/soja), sistema II (trigo/soja e ervilhaca/milho ou sorgo) e sistema III (trigo/soja, ervilhaca/milho ou sorgo e aveia branca/soja). O delineamento experimental foi de blocos ao acaso, com parcelas subdivididas e tres repeticoes. O rendimento de graos e o peso de 1.000 graos de soja cultivada sob plantio direto e sob cultivo minimo foi superior ao de soja cultivada sob preparo convencional de solo com arado de discos e com arado de aivecas. A maior estatura de plantas de soja ocorreu no plantio direto. O rendimento de graos de soja cultivada apos trigo, no sistema II, foi superior ao de soja cultivada apos aveia branca e apos trigo, no sistema III, e apos trigo, no sistema I. O menor rendimento de graos, peso de graos por planta de soja e peso de 1.000 graos ocorreu quando em monocultura (trigo/soja).

Efeito de práticas culturais na conversão e no balanço energéticos

Desenvolveu-se de 1997 a 2003, em Passo Fundo (RS), um experimento constituido de quatro sistemas de manejo de solo (plantio direto, cultivo minimo, preparo convencional de solo com arado de discos e preparo convencional de solo com arado de aivecas) e de tres sistemas de rotacao de culturas: sistema I (trigo/soja); sistema II (trigo/soja e ervilhaca/milho ou sorgo) e sistema III (trigo/soja, ervilhaca/milho ou sorgo e aveia branca/soja). O delineamento experimental foi o de blocos ao acaso, com parcelas subdivididas e tres repeticoes. A parcela principal foi constituida pelos sistemas de manejo de solo, e as subparcelas, pelos sistemas de rotacao de culturas. Neste trabalho, apresentam-se a conversao energetica (energia disponivel/energia consumida) e o balanco energetico (energia disponivel - energia consumida) no periodo de 7 anos. No sistema plantio direto houve conversao e balanco energeticos (72,44 e 190.766 MJ ha-1) superiores ao cultivo minimo (64,06 e 167.349 MJ ha-1), aos preparos convencionais de solo com arado de discos (54,35 e 134.982 MJ ha-1) e com arado de aivecas (52,02 e 128.159 MJ ha-1) respectivamente. O trigo em rotacao de culturas foi mais eficiente energeticamente do que a monocultura desse cereal. Na cultura de milho foi observada maior eficiencia energetica.

Desempenho agronômico de trigo cultivado para grãos e duplo propósito em sistemas de integração lavoura-pecuária

O objetivo deste trabalho foi avaliar a produtividade e os componentes de producao de trigo cultivado para graos e duplo proposito em sistemas de integracao lavoura-pecuaria (ILP), em plantio direto. A produtividade de graos dos dois tipos de trigo e os componentes de producao do trigo para producao de graos foram avaliados nos anos agricolas de 2003 a 2008, em um Latossolo Vermelho distrofico tipico, em Coxilha, RS, nos sistemas de rotacao: 1, trigo/soja e ervilhaca/milho; 2, trigo/soja e pastagem de aveia-preta/milho; 3, trigo/soja e pastagem de aveia-preta/soja; 4, trigo/soja e ervilha/milho; 5, trigo/soja, triticale de duplo proposito/soja e ervilhaca/soja; e 6, trigo/soja, aveia-branca de duplo proposito/soja e trigo de duplo proposito/soja. Utilizou-se o delineamento de blocos ao acaso, com quatro repeticoes. Nao houve diferenca entre as medias dos componentes de producao (numero de espigas, numero de graos por espiga e massa de graos) do trigo para producao de graos, nos diferentes sistemas ILP. Os sistemas 2, 3, 4 e 5 proporcionaram maior produtividade do trigo para graos em comparacao ao 6. Nao ha diferenca significativa na produtividade de graos, na massa hectolitrica e na massa de mil graos, entre os trigos cultivados para producao de graos e para duplo proposito.

Efeito de sistemas de manejo de solo e de rotação de culturas na fertilidade do solo, após vinte anos

ABSTRACT SOIL TILLAGE AND CROP ROTATION SYSTEMS ON SOIL FERTILITYATTRIBUTES AFTER TWENTY YEARS Long term field studies on crop rotation and soil tillage systems under Brazilian conditions are scarce. Soilfertility characteristics were assessed after twenty years (1985 to 2005) on a typical dystrophic Red Latosol locatedin Passo Fundo, in Rio Grande do Sul, the southernmost state of Brazil. Four soil tillage systems (STS) – 1) no-tillage, 2) minimum tillage, 3) conventional tillage using disk plow followed by disk harrow, and 4) conventionaltillage using moldboard plow followed by disk harrow – and three crop rotation systems (CRS): I (wheat/soybean),II (wheat/soybean and common vetch/corn), and III (wheat/soybean, common vetch/corn, and white oat/soybean)were evaluated, including as check a fragment of subtropical forest (FST). A randomized complete block design,with split-plots and three replicates, was used. The main field plots (4 x 90 m) in a total of 12, were the soil tillagesystems, whereas the subplots (4 x 10 m), in a total of 72 comprised the crop rotation systems. Values of soil pH,soil organic carbon, extractable P, and exchangeable K were affected by soil tillage systems (STSs). Higher levelsof soil organic matter and contents of soil carbon, extractable P, and exchangeable K were observed in the 0-0,05m layer for the no-tillage system. No statistical differences were found in soil organic matter levels between no-tillage and tropical forest, in any soil layer. Values of soil organic matter, P, and K were higher in the 0-0,05 mlayer, when compared to the ones observed in the 0,15-0,20 m layer, in no-tillage and II and III CRSs. Values ofpH, Ca, P, and K observed in all STSs and CRSs were higher than in the tropical forest area.

Efeito de integração entre lavoura e pecuária, sob plantio direto, em alguns atributos físicos do solo após dez anos

Even though raising cattle at crop fields can increase soil compaction, there is scarce information on this problem. This study aimed to evaluate some physical characteristics of soil in a typical Dystrophic Red Latosol (typical dystrophic Hapludox) in the county of Coxilha, State of Rio Grande do Sul, Brazil, after ten years of establishment of six ley farm production systems. The treatments were arranged in blocks with four replications. We also evaluated the fertility of the soil of a subtropical forest fragment adjacent to the experiment. Both winter and summer crops were established under no-tillage. Cropping systems and soil of different sampling depths were compared using the orthogonal contrast procedure. We compared the systems and values of the physical characteristics of soil in each system in the layers of 0.0-0.05 m or 0-0.02 m and also 0.10-0.15 m. Soil bulk density and penetration resistance were lower in the layer of 0-0.05 m or 0-0.02 m. The subtropical forest showed highest soil bulk density and soil penetration resistance and lowest total porosity and macroporosity than most systems studied. The soils under different ley farm production systems, despite showing signs of degradation, did not reach levels considered critical to the development of crops. The system wheat/soybean and black oat + vetch + rye grass/pearl millet pasture (IV) presented the worst physical attributes to plant development.

Atributos físicos do solo em sistemas de manejo de solo e de rotação de culturas

Evaluation and quantification of soil use impact on its physical quality are important to achieve sustainable cropping systems. Soil physical attributes were assessed after twenty years of implementation (1985 to 2005) on a typical Dystrophic Red Latosol (Rodic Hapludox) located in Passo Fundo, Rio Grande do Sul State, Brazil. Four soil tillage systems were evaluated: 1) no-tillage; 2) minimum tillage; 3) conventional tillage using a disk plow plus disk harrow, and 4) conventional tillage using a moldboard plow plus disk harrow. Three crop rotation systems were evaluated: I (wheat/soybean), II (wheat/soybean and common vetch/corn or sorghum), and III (wheat/soybean, common vetch/corn or sorghum and white oats/soybean). A randomized complete block design, with split-plots and three replicates, was used. The main plots were formed by the soil tillage systems, while split-plots were composed by crop rotation systems. As control, soil samples were collected in a subtropical forest fragment adjacent to the experiment. Soil tillage systems and crop rotation systems influenced soil physical parameters when compared to the samples collected in a fragment of subtropical forest. During four years (2001 to 2005) the physical attributes were altered among different soil tillage management. The no-tillage system (PD) presented higher soil bulk density and microporosity in comparison to the other systems, mainly in 0.10 to 0.15 m layer, characterizing high soil compaction levels. Crop systems did not promote favorable changes in physical attributes independent of the type of soil management.

Caracterização, potencial agrícola e perspectivas de manejo de solos leves no Brasil

Light soils occupy 8% of the Brazilian territory and are especially expressive in the new and last agricultural frontier in Brazil: the Matopiba region – in the states of Maranhão, Tocantins, Piauí, and Bahia –, where they represent 20% of the area. These soils fit into the textural classes of sand and loamy sand or sandy loam, down to 0.75-m soil depth or deeper, and they are mainly represented by Neossolos Quartzarênicos (Quartzipsamments) and, partly, by Latossolos (Oxisols) and Argissolos (Ultisols). The understanding of soil functioning depends on the establishment of distinguishing criteria for: organic matter dynamics; content and mineralogy of the clay fraction; coarse sand and total sand contents, in relation to those of fine sand; mean diameter of the sand fraction; and water retention capacity. These criteria can contribute for the zoning and for the conservation and fertility management of light soils, as well as for the estimation of their agricultural potential. Integrated production systems, such as crop-livestock and crop-livestock-forestry integration, besides no-tillage with crop rotation, mixed forestry planting with legumes, and the use of green manure and cover crops are relevant for the proper management of these soils. The objective of this review was to characterize light soils and to highlight the main challenges regarding their agricultural potential and their conservation and fertility managements, in face of the expansion and consolidation of the new Brazilian agricultural frontier.