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This paper aims to discuss the impact of the introduction of pastures and grazing animals in agricultural systems. For the purposes of this manuscript, we focus on within-farm integrated crop-livestock systems (ICLS), typical of Southern Brazil. These ICLS are designed to create and enhance the synergisms and emergent properties have arisen from agricultural areas where livestock activities are integrated with crops. We show that the introduction of the crop component will affect less the preceding condition than the introduction of the livestock component. While the introduction of crops in pastoral systems represents increasing diversity of the plant component, the introduction of animals would represent the entry of new flows and interactions within the system. Thus, given the new complexity levels achieved from the introduction of grazing, the probability of arising emergent properties is theoretically much higher. However, grazing management is vital in determining the success or failure of such initiative. The grazing intensity practiced during the pasture phase would affect the canopy structure and the forage availability to animals. In adequate and moderate grazing intensities, it is possible to affirm that livestock combined with crops (ICLS) has a potential positive impact. As important as the improvements that grazing animals can generate to the soil-plant components, the economic resilience remarkably increases when pasture rotations are introduced compared with purely agriculture systems, particularly in climate-risk situations. Thus, the integration of the pastoral component can enhance the sustainable intensification of food production, but it modifies simple, pure agricultural systems into more complex and knowledge-demanding production systems.

INTRODUÇÃOO sistema integrado de produção agropecuária em plantio direto (SIPA-PD) é uma alternativa para a recuperação de áreas degradadas em regiões de clima tropical e subtropical, como o Brasil. Essa recupera- ABSTRACT RESUMOção do solo é possível em função da diversidade de culturas e animais que podem ser utilizados nesse sistema. Entretanto, o manejo de animais nas áreas deve ser realizado de maneira adequada, evitando, assim, os efeitos negativos que o pisoteio pode causar ao solo (Hallett et al. 2003, Souza et al. 2010). A presença de animais em áreas de lavoura pode alterar a estrutura física do solo, sendo que a intensidade de pastejo contribui para esse resultado. Este trabalho objetivou avaliar os atributos físicos do solo e a produtividade de soja e braquiária, em sistema integrado de produção agropecuária, sob plantio direto. Os tratamentos foram distribuídos em blocos casualizados, com três repetições, e consistiram de diferentes alturas de manejo do pasto (0,25 m, 0,35 m e 0,45 m) e uma área sem pastejo. Foi determinada a biomassa seca da parte aérea e raiz da soja e braquiária e a produtividade da soja. Amostras de solo foram coletadas nas camadas de 0-5 cm, 5-10 cm e 10-20 cm de profundidade, sendo determinados os seguintes atributos físicos: densidade, porosidade total, macroporosidade, microporosidade, resistência à penetração e diâmetro médio ponderado de agregados. As intensidades de pastejo não interferiram na densidade do solo em nenhuma das camadas. Houve redução da porosidade total após o segundo ciclo de pastejo, na camada de 0-5 cm. O diâmetro médio ponderado de agregados foi menor nas áreas pastejadas nas camadas de 0-5 cm e 10-20 cm e verificou-se aumento da resistência mecânica à penetração em todas as camadas, principalmente para o pastejo a 0,25 m de altura. A quantidade de biomassa seca total (soja + braquiária) e biomassa seca da parte aérea da braquiária foram menores nas áreas pastejadas, no entanto, a produtividade da soja não foi influenciada pelos ciclos de pastejo. PALAVRAS-CHAVE:Glycine max L.; Urochloa ruziziensis; agregação do solo; porosidade do solo.Influence of the integrated crop-livestock system on soil and soybean and brachiaria yieldThe presence of animals in farming areas can affect soil physical structures depending on grazing intensity. This study aimed to evaluate soil physical attributes, as well as soybean and brachiaria yield, under no-tillage, in an integrated crop-livestock system. Treatments were arranged in a complete randomized blocks design, with three replications, and consisted of different grazing heights (0.25 m, 0.35 m and 0.45 m) and a no-grazing area. The shoot and root dry biomass of soybean and brachiaria and soybean yield were evaluated. Soil samples were collected from 0-5 cm, 5-10 cm and 10-20 cm depth layers and the following soil physical attributes were determined: bulk density, total porosity, macroporosity, microporosity, penetration resistance and mean weight diameter of aggregates. Grazing intensities did not affect soil bulk den...

The objective of this work was to evaluate the soil physical and biological properties in an integrated crop-livestock system (ICLS), with or without cattle grazing, in different seasons. The experiment was carried out in the Cerrado biome, in Brazil, in a Rhodic Eutrudox. The treatments consisted of grazing areas (Urochloa ruziziensis) at 0.25, 0.35, and 0.45 m heights (with soybean cultivation after grazing) and of nongrazed areas. The ICLS had no negative effects on soil bulk density, total porosity, macroporosity, and microporosity. After ICLS implementation, the values of soil bulk density decreased, and those of soil macroporosity increased, in the grazed and nongrazed areas. However, after three years, bulk density and macroporosity were reestablished to values similar to those before ICLS implementation. Soil penetration resistance was higher in the ICLS, mainly at 0.00-0.05 m soil depth. After four years, ICLS promoted the increase of microbial biomass C and N and the reduction of the metabolic quotient. The microbial biomass carbon and the metabolic quotient were related to the weighted mean diameter. ICLS benefits to soil physical and biological properties are associated with adequate ICLS implementation, adequate grazing height (0.35 m), and maintenance of soil cover.

Soil mechanical resistance, aeration, and water availability directly affect plant root growth. The objective of this work was to identify the contribution of mechanical and hydric stresses on maize root elongation, by modeling root growth while taking the dynamics of these stresses in an Oxisol into consideration. The maize crop was cultivated under four compaction levels (soil chiseling, no-tillage system, areas trafficked by a tractor, and trafficked by a harvester), and we present a new model, which allows to distinguish between mechanical and hydric stresses. Root length density profiles, soil bulk density, and soil water retention curves were determined for four compaction levels up to 50 cm in depth. Furthermore, grain yield and shoot biomass of maize were quantified. The new model described the mechanical and hydric stresses during maize growth with field data for the first time in maize crop. Simulations of root length density in 1D and 2D showed adequate agreement with the values measured under field conditions. Simulation makes it possible to identify the interaction between the soil physical conditions and maize root growth. Compared to the no-tillage system, grain yield was reduced due to compaction caused by harvester traffic and by soil chiseling. The root growth was reduced by the occurrence of mechanical and hydric stresses during the crop cycle, the principal stresses were mechanical in origin for areas with agricultural traffic, and water based in areas with soil chiseling. Including mechanical and hydric stresses in root growth models can help to predict future scenarios, and coupling soil biophysical models with weather, soil, and crop responses will help to improve agricultural management.

-The objective of this work was to determine whether compaction by tractor traffic in areas managed under controlled traffic can be limiting to corn crop, under different tillage systems, in a Typic Paleudult of medium texture. Two experiments were carried out, one in the field over two crop seasons and another in a greenhouse. The treatments consisted of minimum tillage with chiselling; no-tillage subjected to one, three, or six passes of a tractor weighing 3.8 Mg; and an area without traffic. Evaluations were performed for soil physicohydraulic parameters (soil bulk density, penetration resistance, and water retention curve), root and shoot growth, and grain yield. The agricultural traffic increased bulk density, soil penetration resistance, and water content at field capacity. The highest values for soil penetration resistance (1,600 kPa) and bulk density (1.67 g cm ) in the trafficked soil were not limiting to corn development and increased grain yield for both crop seasons. Tractor traffic of up to six passes is beneficial to corn cultivation, and it increases water availability and corn grain yield.

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