Physical Properties of Soil Structures Identified by the Profil Cultural under Two Soil Management Systems

Soil structure plays an important role in water retention, infiltration capacity, porosity, and penetration resistance. The aim of this study was to evaluate the unsaturated hydraulic conductivity and physical properties of Oxisol soils (bulk density and macro-, micro-, and total porosity) in the structures identified using the profil cultural method in areas under two different management practices (perennial pasture and sugarcane). Three pits were dug in each plot to find out how homogeneous morphological structural units (HMSU) were organized [...]

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title: Soil compaction-N interactions in barley: root growth and tissue composition
abstract: A controlled environment study investigated the interactions between soil compaction and N availability on the growth and root tissue composition of young barley plants. Plants were grown for 14 days in a mixture of sand and calcined clay (fired clay granules) at two levels of compaction (low and high; dry bulk densities of 0.94 and 1.08 g cm −3 respectively) and two levels of N supply (high, resulting in N sufficient plants and low giving plants deficient in N). High compaction reduced total root length by 23%, leaf area by 21% and altered biomass partitioning (reduced leaf area ratio and increased root weight ratio), but had no effect on total biomass production over the time-course of the experiment. By contrast low N supply, reduced root biomass by 42% and shoot biomass by 47%, but had less effect on shoot morphology than compaction. There was no significant interaction between compaction and N supply on growth and biomass partitioning, although towards the end of the experiment, the rate of N uptake per unit root dry weight was reduced by about 50% by high compaction when N supplies were low, but not when they were high. Compaction altered the concentration of some root tissue components independently of N supply. For example, high compaction reduced the concentration of cellulose plus hemi-cellulose by 30% and increased the mineral content by 38%, whilst N supply had no effect. The concentration of several other components was altered by compaction and N supply in the same direction. Both high compaction and low N supply increased the lignin concentration whilst reducing the concentration of organic N compounds and nitrate, thereby increasing the C:N and lignin:N ratios. Compaction and low N supply increased C:N by a factor of 1.3 and 1.8 respectively, whilst the lignin:N ratio was increased by 1.7 and 2.1 respectively. Thus, both compaction and low N availability altered root tissue composition in a way that might reduce the rate of root degradation by soil microbes. The implications of these findings for modelling nutrient cycling are briefly discussed.

title: Long-term rotation and tillage effects on soil structure and crop yield
abstract: Tillage and rotation are fundamental factors influencing soil quality and thus the sustainability of cropping systems. Many studies have focused on the effects of either tillage or rotation, but few have quantified the long term integrated effects of both. We studied the issue using a 30-year old long-term rotation and tillage treatment experiment on a Canadian silt loam soil. Topsoil measurements were carried out for three different rotations: R1, (C–C–C–C) continuous corn (Zea mays L.), R6, (C–C–O(RC), B(RC)) corn, corn, oats (Avena fatua L.) and spring barley (Hordeum vulgare L.) and R8, (C–C–S–S) corn, corn, soybean (Glycine max L.), soybean. A red clover (Trifolium pretense L.) cover crop was under seeded in oats and spring barley in R6. In 2010, first year corn was grown in R6 and R8. The tillage treatments included no tillage, NT and mouldboard ploughing, MP. Topsoil structural quality was visually evaluated in early June and mid October. Minimal disturbed soil cores collected in early June were used for X-ray CT scanning and to quantify water content and porosity. Soil friability was determined on the soil samples using a drop shatter test. Crop yield was determined and correlated to the soil quality estimates. We found significant effect of both rotation and tillage on visual soil structure at both times of assessment. Poor soil structure was found for NT except when combined with a diverse crop rotation (R6). The soil core pore characteristics data also displayed a significant effect of tillage but only a weak insignificant effect of rotation. The drop shatter results were in accordance with the visual assessment data. Crop yield correlated significantly with the visual soil structure scores. We conclude that a diverse crop rotation was needed for an optimal performance of NT for the studied soil.

title: Capacity and intensity soil aeration properties affected by granulometry, moisture, and structure in no-tillage soils
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title: Conceptual framework for capacity and intensity physical soil properties affected by short and long-term (14 years) continuous no-tillage and controlled traffic
abstract: Recent studies have shown harmful effects of soil compaction in no-tillage system (NTS), but there are indications that soil structure improves with time of NTS adoption. We formulated the hypothesis that topsoils of NTS initially have worse soil physical conditions than those under conventional systems, but these conditions gradually improve with time also down to deeper depth, even when the soil is wheeled by farm machinery. Our objective was to evaluate the effect of a long-term no-tillage system and machine traffic on soil mechanical and hydraulic properties. The treatments and soil conditions consisted of five periods since the last conventional tillage (or age of NTS) in a Hapludox: 0.2,1.5, 3.5, 5 and 14 years, with and without traffic; named recent tillage, and initial, intermediate, transition and stabilized NTS phases. Soil samples were collected from soil layers 0-7, 7-14 and 14-21 cm depth to determine soil porosity, precompression stress, compressibility coefficient, saturated hydraulic conductivity, air permeability, water retention curve, bulk density and organic carbon. Conventional tillage of soil previously under no tillage significantly affected soil capacity properties, resulting in high macroporosity and deformation susceptibility, low bulk density and precompression stress. Intensity properties were affected initially by an increased soil pore obstruction, negatively affecting air permeability and saturated hydraulic conductivity, from 0 to 21 cm soil depth. However, after five years of no-tillage there was an increase in microporosity and, although small, in soil organic carbon, especially in the 0-7 cm soil layer; thus, soil water retention and soil intensity properties (like soil water and air permeability) were also improved, regardless of farm machinery traffic. Over time, soil reconsolidation occurred, which resulted in reduction of the compressibility coefficient and degree of compactness, mainly in the upper layers (07 and 7-14 cm). However, in the deepest layer with the least disturbance, the degree-of-compactness and bulk density increased. The evolution of physical properties and processes (from recent tillage to stabilized NTS phase) for no-tilled soil is proposed for controlled and uncontrolled traffic systems as a framework based on field data for capacity and intensity soil properties. The process of creating aggregates is represented, at first, by an increased number of contact points before they are re-loosened and strengthened at the same time by a rearrangement of particles, reducing aggregate bulk density but increasing soil strength at the same time. The framework is divided into 4 phases: initial (1.5 years), intermediary (3.5 years), transitional (5 years), and stabilized (14 years) conditions.

title: Entropy and sustainability
abstract: Soil–plant systems exchange both energy and matter with their surroundings and are consequently open systems thermodynamically. They should therefore tend towards a steady state described by non-equilibrium thermodynamics and characterized by minimum production of entropy. The theory surrounding the principle of minimum entropy production provides a good analogue of the behaviour of natural and agricultural ecosystems subjected to perturbations. Entropy-increasing processes are those that degrade complex, ordered structures of large molecular weight to small molecules such as CO2, NH3 and H2O. Processes such as photosynthesis that build small molecules into larger ones lessen entropy. These ordering processes are permitted by thermodynamic work performed when heat is transferred from the sun. They depend critically on the capacity of the system for self-organization, which is identified with its biological potential. Several of the small molecules are environmentally undesirable in excess. This, together with the theoretical considerations above, suggests that minimum production of entropy should be a criterion of sustainability. It implies that agricultural systems should be allowed to become steady states where possible and that maintaining the biological potential is essential. An ‘audit of small molecules’ is suggested as a way of assessing sustainability.

title: Soil bulk density and porosity of homogeneous morphological units identified by the Cropping Profile Method in clayey Oxisols in Brazil
abstract: Soil structure is important to root development and crop yield. The objective of this study was to test the Cropping Profile Method in Brazilian soils, in order to evaluate the soil structure in the field. Grouped different structures determined by the Cropping Profile Method were compared to laboratory determinations for soil bulk density, total porosity and mercury porosity. The study was conducted in clayey Oxisols submitted to different uses and management including annual crops, orchards and natural forests in the State of Parana, southern Brazil. Homogeneous morphological units (HMUs) were determined in trenches using the Cropping Profile Method, and the different structures were grouped as: (a) non-compacted; (b) compacted; (c) in-process-of-compacting. Results of field evaluation were compatible with those obtained in the laboratory. More compacted and in-process-of-compacting structures corresponded to soil bulk density values of 1.42 and 1.33 Mg m −3 , which were significantly higher than the 1.18 Mg m −3 value obtained for soil bulk density in non-compacted HMU. The total porosity of compacted HMU and in-process-of-compacting HMU was 0.49 and 0.52 m 3  m −3 , respectively. These were significantly lower than the value obtained for the non-compacted HMU (0.60 m 3  m −3 ). The Cropping Profile Method is useful mainly in field research works when it is important to verify the effect of management practices on soil structure.

title: Developments in the “profil cultural” method for an improved assessment of soil structure under no-till
abstract: In France, agronomists have studied the effects of cropping systems on soil structure using a field method that is based on a visual description of the soil structure. This "profil cultural" method was designed as a field diagnostic tool to identify the effects of tillage and compaction on soil structure dynamics. It is of great benefit to agronomists seeking to improve crop management and preserve soil structure and fertility. However, the "profil cultural" method was developed and has mainly been used in conventional tillage systems with regular ploughing. As there has been an increase in the use of various forms of reduced, minimum and no-tillage systems in many parts of the world, it is necessary to re-evaluate this method's ability to describe and interpret soil structure dynamics in no-till or reduced tillage. In these situations, changes in soil structure over time are mainly driven by compaction and by regeneration through natural agents (climatic conditions, root growth and macrofauna), therefore it is important to evaluate the effects of these natural processes on soil structure dynamics. These concerns have led to adaptations and amendments to the initial method based on field observations and experimental work in different cropping systems, soil types and climatic conditions. The description of crack types has been improved and a criterion of biological activity based on the visual examination of clods has been introduced. To test this modified method, a comparison with the initial method was undertaken and its ability to make diagnoses tested in five experiments in France, Brazil and Argentina. The adapted method allowed an improved assessment of the impact of cropping systems on soil functioning when natural processes were integrated into the description.

title: Relating visual evaluation of soil structure to other physical properties in soils of contrasting texture and management
abstract: The sustainability of agricultural systems depends on the evaluation and monitoring of soil use and tillage in order to mitigate soil degradation. The visual evaluation of soil structure (VESS) was developed to provide a quick, simple and easily understood test to enable researchers, farmers and consultants to score soil quality. In this paper we test the hypothesis that soil structural quality, as specified by VESS (Sq), is sensitive enough to identify differences in structure, resulting from soil management, in and between layers of topsoil. The Sq score ranges from 1 (good) to 5 (poor soil structure). Improvements have already been made to this method, but we wished to test the validity of Sq results compared with other indicators of soil physical quality. Our aims were (1) to evaluate the usefulness of VESS to compare layering of topsoil structure under different soil management and (2) to identify which soil physical properties Sq most closely relates to. We chose to work on soils of contrasting texture in response to criticism that the test works well only on medium-textured soils. In our first experiment, we assessed Scottish soil from native forest that had never been cropped and from arable soils just after harvest so where there was a visible difference between soil tracked or not tracked during harvesting operations. Soil qualities measured were soil resistance to penetration (SR), bulk density (Bd) and air permeability (Ka). In our second experiment we compared the least limiting water range (LLWR) with VESS in a Brazilian Oxisol under no-tillage. VESS showed the differences between the treatments and layers of topsoil. Sq increased with SR and Bd but decreased with air permeability. Results for LLWR showed that for Sq ≥ 3.5, the LLWR was zero, indicating soil physical condition highly restrictive to plants. Harvest is a time of significant soil compaction and the VESS test detected compaction even where it was not visible at the surface and as such may prove useful in diagnosing and remediating compaction and assessing suitability for minimum tillage.

title: Soil structure and its influence on microbial biomass in different soil and crop management systems
abstract: A B S T R A C T Methods for assessment of soil structure in the field are useful for determining the sensitivity of soil to different management systems. Soil and crop management have a fundamental role in the maintenance and improvement of soil quality, as they have a direct influence its structure and on microbiota habitats. The aim of this study was to qualify and quantify homogeneous morphological units (HMUs) in a dystroferric Red Latosol, in a 22-year experiment with treatments consisting of a no-tillage planting system (NT), no-tillage with chiseling every 3 years (NTC) and conventional tillage (CT), using crop rotation (CR) [with five different crop species in 3 years] and succession systems (CS) [only two crop species]. The NT and NTC treatments presented HMUs with a continuous and cohesive structure and increased visible porosity at the surface, and continuous and cohesive units with lower porosity below this layer. The surface layer of the NT treatment presented free units made up of small and medium sized clods, and below this layer, compact, continuous units with little porosity. The soil management systems with crop rotation presented less compact units and roots with fewer morphological deformities than in the treatments with succession systems. Significantly higher levels of carbon and nitrogen microbial biomass (CMB and NMB) were observed in the HMUs in NT and NTC systems under both crop rotation and succession systems, and these had higher visible porosity than the units found in the CT system. On average, HMUs in the NT and NTC treatments presented 20% more CMB and 51% more NMB than in the CT treatment. NMB was the parameter most highly affected by the soil management. At depths of 0– 20 cm, total organic carbon (TOC), was higher by an average of 21% than in the NT and NTC treatments. Total nitrogen (TN) was also affected by the soil management, increasing by an average of 50% in the NT and NTC treatments. This demonstrates how the tillage of the soil exposes the organic matter in the aggregates to oxidation and nitrogen mineralization.

title: A compartmental model to simulate temporal changes in soil structure under two cropping systems with annual mouldboard ploughing in a silt loam
abstract: A practical model of the soil structure dynamics in ploughed fields can be a powerful aid to farmers attempting to optimise their management practices. This paper describes a compartmental model that simulates the changes over several years in an indicator of the effects of cropping systems on soil structure. This indicator, the proportion of severely compacted clods in the ploughed layer, was measured in two plots at the INRA Experimental Centre at Grignon (Yvelines, France), where two cropping systems produced very different compaction conditions in a silt loam. The ploughed layer was considered to be a set of elementary compartments delimited by the wheel tracks and actions of tillage tools. The percentage of severely compacted clods in each elementary volume changed with time due to transfer between compartments during mouldboard ploughing, compaction and fragmentation. The proportion of severely compacted clods changed exponentially until it reached a plateau, after about 8 years. The equilibrium values of the indicator were very similar to those measured in the experimental plots. The model was very sensitive to the rate at which severely compacted clods were lost, probably because the vertical distribution of these clods in the soil profile was not taken into account in this compartmental model. The model in its present state can be used to compare the effects on soil structure of various technical changes.

title: Evaluation of soil structure in the framework of an overall soil quality rating
abstract: Soil structure is an important aspect of agricultural soil quality, and its preservation and improvement are key to sustaining soil functions. Methods of overall soil quality assessment which include visual soil structure information can be useful tools for monitoring and managing the global soil resource. The aim of the paper is: (i) to demonstrate the role of visual quantification of soil structure within the procedure of the overall soil quality assessment by the Muencheberg Soil Quality Rating (M-SQR), (ii) to quantify the magnitude and variability of soil structure and overall M-SQR on a number of agricultural research sites and (iii) to analyse the correlations of soil quality rating results with crop yields. We analysed visual soil structure and overall soil quality on a range of 20 experimental sites in seven countries. To assess visual soil structure we utilised the Visual Soil Assessment (VSA) and Visual Evaluation of Soil Structure (VESS) methods. Results showed the feasibility and reliability of both VSA and VESS methods and the overall soil quality M-SQR rating approach to give scores and classes which characterised the soil potential for cropping. The structure status of soil can be reliably assessed by these procedures. In soils with clay contents > 30% unfavourable soil structure could not be reliably recognised by measurements of the dry bulk density, but significantly by evaluation of visual soil structure. Structure scores were clearly associated with the drainage status of soil. More than 70% of the variability of crop yields at a given intensity of input may be explained by the overall M-SQR-score which includes information on soil texture, relief and climate in addition to soil structure. We conclude that methods of visual soil assessment are useful diagnostic tools for monitoring and controlling agricultural soil quality over different scales, ranging from within-fields to global. Controlling the drainage status of land and action of machinery at appropriate drainage states are pre-conditions for preserving a suitable soil structure.

title: Modelling structural changes in tilled topsoil over time as a function of cropping systems
abstract: The optimization of tillage practices requires the evaluation of the long-term effects of cropping on changes in soil structure. A model is presented that simulates changes in soil structure in the tilled horizons of cultivated fields. The indicator of soil structure that we have modelled is based on a morphological description of the structure and the assessment of the percentage of severely compacted zones and clods showing no visible porosity in the tilled layer of a soil profile. The model takes into account the spatial variation of the structure induced by traffic and tillage. Severely compacted zones are created under wheel tracks, they are cut and transferred during ploughing, and they are fragmented into fine soil during secondary tillage. The model was evaluated over 7 years in a field trial on loamy soil in three experimental plots, where the crop sequences and field operations induced contrasted changes in the percentage of severely compacted zones and clods. The model satisfactorily reproduced the changes with time of the indicator, and the correspondence between simulated and observed values was fairly good (r= 0.82, model efficiency = 0.61). However, some variations from one year to the next were poorly predicted. The sensitivity analysis did not suggest modification to the parameter values but showed that the performance of the model could be improved if the fragmentation (due to weather and tillage) were more precisely described in the model. Nevertheless the present version of the model and the corresponding simulation program (SISOL) can be used to compare the effects of different technical choices on the evolution of soil structure.

title: Apport de l'électrodialyse à l'étude de l'influence de l'organisation du sol sur la disponibilité des éléments minéraux dans les sols tropicaux
abstract: Mineral elements were separated by electrodialysis from soil suspensions or clods of porous or nonporous samples taken in cultivated ferrallitic soils. These separations showed the influence of the organization of the soil on the mobility of some elements, calcium especially and magnesium to a lesser degree. These results indicated that the availability of mineral elements might be overestimated in compacted soils especially, when assessed solely on soil suspensions.

title: SOIL AGGREGATION UNDER DIFFERENT MANAGEMENT SYSTEMS
abstract: Considering that the soil aggregation reflects the interaction of chemical, physical and biological soil factors, the aim of this study was evaluate alterations in aggregation, in an Oxisol under no-tillage (NT) and conventional tillage (CT), since over 20 years, using as reference a native forest soil in natural state. After analysis of the soil profile (cultural profile) in areas under forest management, samples were collected from the layers 0-5, 5-10, 10-20 and 20-40 cm, with six repetitions. These samples were analyzed for the aggregate stability index (ASI), mean weighted diameter (MWD), mean geometric diameter (MGD) in the classes > 8, 8-4, 4-2, 2-1, 1-0.5, 0.5-0.25, and < 0.25 mm, and for physical properties (soil texture, water dispersible clay (WDC), flocculation index (FI) and bulk density (Bd)) and chemical properties (total organic carbon - COT, total nitrogen - N, exchangeable calcium - Ca2+, and pH). The results indicated that more intense soil preparation (M < NT < PC) resulted in a decrease in soil stability, confirmed by all stability indicators analyzed: MWD, MGD, ASI, aggregate class distribution, WDC and FI, indicating the validity of these indicators in aggregation analyses of the studied soil.

title: Simple field method for determining unsaturated hydraulic conductivity
abstract: A new method is proposed for determining in situ unsaturated hydraulic conductivities from unsaturated infiltration measurements made at several tensions on the same infiltration surface. Wooding's equation for steady-state unconfined infiltration rates is used in calculating hydraulic conductivities. Hydraulic conductivities calculated with the new method are consistent with unit gradient laboratory measurements of saturated and unsaturated hydraulic conductivity. This simple field method is potentially valuable because it is faster than unit gradient laboratory methods, and it is less disruptive of pore continuity than other field infiltration techniques. R OF SOIL WATER INFILTRATION and SUbSUrface water movement are important to researchers developing soil management practices to minimize potential groundwater contamination from land applied chemicals. A simple and rapid field technique of determining field unsaturated hydraulic conductivity would be useful in achieving this objective. Field and laboratory techniques for measurement of unsaturated hydraulic properties of soil were described by Green et al. (1986) and by Klute and Dirksen (1986), respectively. Solution of unsaturated flow problems generally requires experimental determination of the relationship between hydraulic conductivity and water potential or water content. Field methods used to obtain these relationships include the instantaneous profile method, steady-flux methods (with sprinkler irrigation or artificial crusts), sorptivity measurements, and use of tension infiltrometers (Clothier and White, 1981; Ankeny et al., 1988, 1989; Elrick et al., 1988a; White and Perroux, 1987, 1989; Smettem and Clothier, 1989). Because instantaneous profile and steady-flux techniques require laborious installation of tensiometers or neutron probe access tubes, sample numbers and the extensiveness of a site characterization can be limited. Sorptivity is an unsaturated soil parameter sometimes measured in the field (Green et al., 1986). Although sorptivity measurements are fast and simple, these measurements usually require that initial water content be known. White and Perroux (1989) have proposed a laboratory method for calculating unsaturated hydraulic conductivity from sorptivity measurements. Their method, however, requires air drying the sample between measurements at different tensions, which increases experimental time and may cause wetting/drying effects on soil structure. The Guelph infiltrometer (Soilmoisture Equipment Corp., Santa Barbara, CA) compares infiltration rates for difM.D. Ankeny, Daniel B. Stephens & Assoc., 4415 Hawkins NE, Albuquerque, NM 87109; M. Ahmed, Bangladesh Univ. of Engineering and Technology, Dhaka-1000, Bangladesh; T.C. Kaspar, National Soil Tilth Lab., Ames, IA 50011; and R. Horton, Dep. of Agronomy, Iowa State Univ., Ames, IA 50011.   Corresponding author.  (1991). ferent radii surface disks and does not require driving a ring. Different soil surface areas, however, are being compared, which may introduce spatial variability associated with the different soil surfaces. A field method to measure in situ hydraulic conductivity at low water tensions is needed for studies of macroporosity and water flow in agricultural soils. The desired criteria for such a method are: 1. Only steady-state infiltration rate measurements are needed. Knowledge of the initial water potential or content should not be required. 2. Soil pore structure should not be disturbed by driving a ring into soil to obtain one-dimensional flow. This way, larger pores are not truncated or collapsed and infiltration through larger pores is less likely to be underestimated. 3. Measurements should be taken on the same soil surface. Measurements taken by using different radii (e.g., Elrick et al. 1988a) are more dependent on the assumption of soil homogeneity. 4. Calculation of hydraulic conductivities should be straightforward. We present a simple scheme for determination of in situ hydraulic conductivity that meets these criteria.

title: Visual soil structure quality assessment on Oxisols under no-tillage system
abstract: Methods for evaluation the soil structure quality based on field evaluations are useful to determine strategies for soil management, with the advantage of requirement the use of little equipment and the possibility of immediate interpretation. A new methodology was recently developed to temperate soils for this purpose, called Visual Soil Structure Assessment (Ball et al., 2007). It was tested the hypothesis that it is possible to apply and advance in the interpretation of the results from use of Visual Soils Structure Assessment in cultivated Oxisols. Therefore the goal of this study was to apply, evaluate and enhance the potential of the methodology developed by Ball et al. (2007) in two Oxisols under long-term, no-till in Parana State, Brazil, as well as in a soil under native forest, used as reference of soil structural quality. The proposed implementation and progress in terms of structural quality for the distinct layers provided an assessment of soil physical quality more practical and detailed. This is useful to support the selection of appropriate techniques for mechanical and biological management systems in order to achieve the physical quality of soil suitable for crop development. Visual scores of soil structure quality proposed by Ball et al. (2007) can be applied to Brazilian Oxisols cultivated under no-tillage system.

title: Influência da posição relativa à linha de cultivo sobre a densidade do solo em dois sistemas de manejo do solo
abstract: Bulk density is a soil parameter that can be easily measured, associated to other intrinsic soil properties such as texture and organic matter. Pore size distribution, soil resistance to root penetration, and available water are also related with bulk density. When comparing tillage systems, bulk density is frequently used. However, tillage and plant effects on bulk density variability have not been addressed. Bulk density variability is caused by traffic, wetting and drying processes, as well as root system activity. The overall objective of this research was to evaluate bulk density distribution in two tillage systems in a soil cropped with corn. The study was conducted on a heavy clay Oxisol under no-till and conventional tillage. Sampling was carried out on a transect that crossed the corn rows, taken at two positions (row and interrow). To assess the tillage and position effects on bulk density, t tests were used. Spectral analysis was performed to evaluate whether bulk density variability was systematic. The results indicated that bulk density was influenced by position regardless of the tillage system. Bulk density variability was systematic and it was related to position.

title: Sampling equipament for soil bulk density determination tested in a Kandiudalfic Eutrudox and a Typic Hapludox
abstract: 3 Pos-Graduando em Irrigacao e Drenagem - USP/ESALQ.  In spatial variability studies of soil physical properties the influence of different samplers on the results is seldomly taken into account. The objective of this work was to evaluate the performance of five different types of sampling equipment for soil bulk density determination, in two different soils a Kandiudalfic Eutrudox and a Typic Hapludox, both of Piracicaba, SP, Brazil. Equipment used for soil undisturbed sampling were: (i) Uhland soil sampler; (ii) Kopecky's Ring; (iii) soil core sampler, model "Soil Moisture"; (iv) soil core sampler Bravifer AI-50 and (v) soil core sampler Bravifer AI-100. The sampling was made in 4 grids of 1m2 , each with 25 sampling points, with five replications, resulting 100 samples for each soil. It was concluded that the sampling techniques can influence soil bulk density distributions, mainly in the case of clayey soils (Kandiudalfic Eutrudox). The Kopecky's Ring presented larger soil density values, overestimating this property for the two soils studied. The soil core sampler Bravifer AI-50 presented results closest to the overall average of the Typic Hapludox.

title: Least limiting water range and soybean yield in a long-term, no-till, integrated crop-livestock system under different grazing intensities
abstract: Crop-livestock integrated systems possess some uniqueness in soil and plant hydro-physical properties and processes. To obtain a better understanding of these systems, it is necessary to evaluate them with indices that take into account several attributes. Our study aimed to evaluate the efficiency of the least limiting water range in determining the influence of grazing intensities on soybean yield in an Oxisol managed in a long no-till, integrated soybean-beef cattle system. We evaluated an 11 year trial located in southern Brazil, with soybean summer cropping and black oat + Italian ryegrass winter grazing and different winter grazing intensities, namely intensive, moderate and no grazing. Intensive grazing only results in the most superficial soil layer compaction. Long-term moderate grazing, on the other hand, leads to intermediate compaction, not negatively affecting surface or subsurface soil physical properties. The least limiting water range is an inadequate indicator of soil physical quality in integrated soybean-beef cattle system, provided no direct relations with soybean yields. Under normal rainfall conditions, soybean yield depend mainly on rainfall amount and distribution, rather than on soil quality.

title: Qualidade química e física do solo sob vegetação arbórea nativa e pastagens no Pantanal Sul-Mato-Grossense
abstract: The search for improved productivity of livestock has stimulated deforestation of forested areas in the Pantanal for pasture planting, raising concerns about the sustainability of the natural resources. To study some aspects of land use in the Pantanal of Mato Grosso, Brazil, this study aimed to evaluate the changes in chemical and physical soil properties due to the conversion of native tree vegetation in pasture, and the exposure of native pasture to a continuous grazing system. The environments of the study consisted of three remnants of native vegetation, represented by a semi-deciduous forest (NF) and two Cerrado (CE1 and CE2) areas, three 27, 26 and 11-year-old Brachiaria decumbens pastures, planted to replace FN , CE1 and CE2, respectively, and a native pasture with predominance of Mesosetum chaseae and Axonopus purpusii, under three different grazing systems (continuous and ungrazed for 3 and 19 years). Disturbed and undisturbed soil samples were collected from each study environment, in the layers 0-10 and 10-20 cm, with three replications. The replacement of native tree vegetation by pasture and by continuous grazing of native pasture resulted in a reduction of the soil chemical quality, evidenced primarily by a loss of soil organic matter, particularly in the layer 0-10 cm. Although the soil physical quality also tends to decrease under cultivated and native pasture under continuous grazing, the values of bulk density, total porosity, macroporosity, microporosity, hydraulic conductivity of saturated soil and soil penetration resistance did not reach levels considered critical for root development.