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Brazil is the worlds largest sugarcane producer and is committed to promoting sugarcane production in the following years. However, sugarcane expansion can degrade soil physical quality and related soil functions due to management practices such as conventional tillage and random machinery traffic. Conversely, conservation tillage practices such as reduced tillage and the adoption of traffic-free seedbed zones have been investigated as management practices that can improve soil structure and, consequently, its functional capacity. The hypotheses of this study are that i) sugarcane expansion under conventional tillage on pasture areas degrades soil structure and reduces the related soil functions and ii) the adoption of reduced tillage and traffic-free seedbed zones instead of conventional tillage improves soil structure and consequently the related soil functions. The overall objective of this study was to evaluate the effects of a typical land-use change sequence (native vegetation pasture sugarcane) on soil functions for sugarcane expansion and the adoption of different tillage practices in its cultivation. To meet this objective, this study has assessed i) the effects of a typical land-use change sequence for sugarcane expansion on soil physical quality and water dynamics in contrasting soil textures, ii) soil water availability and air flux indicators in two soils with contrasting textures under conventional and reduced tillage practices associated with random and without machinery traffic, iii) the effects of conventional and reduced tillage practices with random and without machinery traffic on soil structure, and iv) the impacts of agricultural traffic control on soil physical properties and related functions under contrasting soil textures. The findings showed that conversion from native vegetation to extensive pasture induced severe degradation in soil physical quality. On the other hand, conversion from pasture to sugarcane did not cause additional degradation on soil structure and soil water dynamics. In general, conventional tillage and reduced tillage under random traffic showed similar soil structure and soil water availability and air fluxes. However, the adoption of reduced tillage and traffic-free seedbed zones improved soil structure regardless of assessment scales (i.e., micro and macro scales) and it also preserved soil water availability and air fluxes. In addition, agricultural traffic control supported soil physical functionality and soil physical quality at the seedbed position and it did not reduce soil physical functionality related to uncontrolled traffic at the sugarcane inter-row position. Lastly, this study identified that adopting reduced tillage and traffic-free seedbed zones are two of the most important pillars for reducing soil compaction in sugarcane fields and, consequently, can contribute positively to provide natures contribution to people. O Brasil é o maior produtor mundial de cana-de-açúcar e está empenhado em promover a produção de cana-de-açúcar nos próximos anos. Contudo, a expansão da cana-de-açúcar pode degradar a qualidade física do solo e suas funções relacionadas, devido a práticas de manejo como o preparo convencional e o tráfego agrícola aleatório. Inversamente, práticas conservacionaistas, tais como o plantio direto e a adoção de zonas livre de tráfego tem sido investigadas como práticas de manejo que podem melhorar a estrutura do solo e, consequentemente, a capacidade do solo em realizar suas funções. As hipóteses deste estudo são que i) a expansão da cana de açúcar manejada com preparo convencional sobre áreas de pastagem extensiva degrada a estrutura do solo reduzindo as suas funções e ii) a adoção do preparo reduzido e zonas livre de tráfego ao invés do preparo convencional melhora a estrutura do solo e, consequentemente, as suas funções. O objetivo geral desta tese foi avaliar os efeitos de uma típica sequência de mudança de uso da terra (vegetação nativa - pastagem - cana-de-açúcar) para a expansão da cana de açúcar nas funções do solo e a adoção de diferentes práticas de manejo no seu cultivo. Para atingir este objetivo, este estudo avaliou i) os efeitos de uma típica sequência de mudança de uso da terra para a expansão da cana-de-açúcar na qualidade física do solo e dinâmica da água em solos com texturas contrastantes, ii) indicadores de disponibilidade de água e fluxos de ar no solo em dois solos com texturas contrastantes sobre preparo convencional e preparo reduzido associado com e sem adoção de zonas livre de tráfego, iii) os efeitos do preparo convencional e preparo reduzido com e sem adoção de zonas livre de tráfego na estrutura do solo, e iv) os impactos do controle de tráfego agrícola nas propriedades físicas e funções do solo relacionadas sob contrastantes texturas do solo. Os resultados mostraram que a conversão da vegetação nativa para pastagem extensiva induziu severa degradação na qualidade física do solo. Por outro lado, a conversão da pastagem para cana-de- açúcar não causou degradação adicional na estrutura do solo e na dinâmica da água do solo. De modo geral, o preparo convencional e preparo reduzido sob tráfego aleatório mostraram similaridade na estrutura do solo, disponibilidade de água e fluxos de ar no solo. No entanto, a adoção do preparo reduzido associado a zonas livre de tráfego melhorou a estrutura do solo independentemente das escalas de avaliação (ou seja, micro e macro escalas), bem como preservou a disponibilidade de água e os fluxos de ar no solo. Além disso, o controle de tráfego agrícola manteve a funcionalidade física do solo e a qualidade física do solo na linha de cultivo e não reduziu a qualidade física do solo em relação ao tráfego aleatório na entre-linha de cultivo da cana-de- açúcar. Por último, este estudo identificou que a adoção do preparo reduzido e zonas livre de tráfego são dois dos pilares mais importantes para reduzir a compactação do solo no cultivo de cana-de-açúcar e, consequentemente, contribuir positivamente para a provisão de serviços ecossistêmicos relacionados a qualidade física do solo.

Removing sugarcane straw to increase bioenergy production can generate significant income to the industry. However, straw contributes to the regulation of soil functions and consequently supports the provision of ecosystem services, such as water flow regulation. Thus, straw removal may hinder the provision of these services, especially in mechanized sugarcane production systems, which have soil compaction problems due to machinery traffic. In this study, we assess a six-year experiment in Brazil with four rates of straw removal: 0 Mg ha−1 (TR), 5 Mg ha−1 (HR), 10 Mg ha−1 (LR), and 15 Mg ha−1 (NR) remaining straw. Using attributes, such as soil bulk density, porosity, water infiltration, runoff, saturated hydraulic conductivity and available water-holding capacity, as indicators of key soil functions, we calculated a soil-related ecosystem service (ES) index for water flow regulation provision. The ES index revealed that water flow regulation was low regardless of the straw management (0.56, 0.63, 0.64 and 0.60 for TR, HR, LR and NR, respectively). It can be a consequence of soil compaction caused by machinery traffic throughout the successive cycle, whose straw was unable to mitigate this issue. Thus, by the end of the sugarcane cycle (sixth ratoon), straw removal had little effect on soil physical and hydraulic indicators, and consequently had little impact on the provision of the soil-related ES associated with water flow regulation. Nevertheless, straw management should be planned to consider other functions and soil-related ES benefited by straw retention.

Soil compaction is a result of soil compression, and this effect depends on the pressure applied and the soil structure. Nevertheless, studies regarding the effects of long-term tillage systems on strengthening of particle bonds are scarce. Thus, we aimed to study the soil bond strengthening due to the age-hardening phenomenon using the soil load support capacity model of an Oxisol managed under different tillage systems in Southern Brazil. Soil samples were collected from three soil layers (0.0–0.10 m; 0.10–0.20 m and 0.20–0.30 m) and five soil tillage systems of conventional tillage; minimum tillage with chiselling performed every year or every three years; and no-tillage for 11 or 24 years. Age-hardening was investigated using the soil load support capacity model. Soil cores were equilibrated at four matric potentials (−6, −33, −100 and −500 kPa) and submitted to uniaxial compression tests to obtain preconsolidation pressure. The soil load support capacity models were affected by the tillage systems. The long-term no-tillage presented the highest soil load support capacity for the same bulk density and water content in all layers, demonstrating greater resistance to additional compaction. Higher preconsolidation pressure values in long-term no-tillage at the same soil bulk density and water content were attributed to the age-hardening phenomena, which increased the number and strength of bonds among soil particles, leading to higher soil cohesion. Longer time under no-tillage improves the soil structure and soil load support capacity. Thus, soil mobilization strongly affected the soil structure by breaking particle bonds leading to the greater compaction.

Brazil is the world&rsquo, s largest sugarcane producer with projections for expanding the current area by 30% in the coming years, mainly in areas previously occupied by pastures. We assess soil water changes induced by land-use change (LUC) for sugarcane expansion in the central-south region of Brazil. For that purpose, soil samples were collected in a typical LUC sequence (native vegetation&ndash, pasture&ndash, sugarcane) in two contrasting soil textures (i.e., sandy and clayey). Soil hydro-physical properties such as pores size distribution, bulk density, soil water content, water tension, and drainage time at field capacity, plant-available water, and S-index were analyzed. Our data showed that long-term LUC from native vegetation to extensive pasture induced severe degradation in soil physical quality and soil water dynamics. However, conventional tillage used during conversion from pasture to sugarcane did not cause additional degradation on soil structure and soil water dynamics. Over time, sugarcane cultivation slightly impaired soil water and physical conditions, but only in the 10&ndash, 20 cm layer in both soils. Therefore, we highlight that sustainable management practices to enhance soil physical quality and water dynamics in sugarcane fields are needed to prevent limiting conditions to plant growth and contribute to delivering other ecosystem services.

In agricultural crops, the use of swine and poultry waste as organic fertilizers results in gains in the productivity and reduction of production costs, but it may also change the physical properties and mechanical behavior of the soil, either increasing or reducing its quality. This study aimed to investigate the influence of applying increasing doses of liquid swine manure (160 m³ ha-1 year-1, 320 m³ ha-1 year-1 and 480 m³ ha-1 year-1) and poultry litter (6 Mg ha-1 year-1, 12 Mg ha-1 year-1 and 18 Mg ha-1 year-1), along four years, on the physical-mechanical properties and organic carbon content of a very clayey Rhodic Eutrudox. The application of liquid swine manure and poultry litter increased the surface soil organic carbon contents. The soil density decreased, whereas the total porosity and macroporosity increased, with the addition of liquid swine manure and poultry litter. There were no significant changes in the soil susceptibility to compaction. RESUMO A adubação orgânica das culturas agrícolas com resíduos oriundos da suinocultura e da avicultura resulta em ganhos de produtividade e redução nos custos de produção, porém, pode alterar as propriedades físicas e o comportamento mecânico do solo, aumentando ou reduzindo a sua qualidade. Objetivou-se investigar a influência da aplicação superficial de doses crescentes de dejetos líquidos de suínos (160 m³ ha-1 ano-1, 320 m³ ha-1 ano-1 e 480 m³ ha-1 ano-1) e de cama de aviário (6 Mg ha-1 ano-1, 12 Mg ha-1 ano-1 e 18 Mg ha-1 ano-1), ao longo de quatro anos, sobre as propriedades físico-mecânicas e carbono orgânico de um Latossolo Vermelho muito argiloso. As aplicações de dejeto líquido de suínos e de cama de aves aumentaram os teores superficiais de carbono orgânico do solo. A densidade do solo reduziu-se, enquanto a porosidade total e a macroporosidade aumentaram, em função das adições de dejeto líquido de suínos e de cama de aves. Não houve alterações significativas na suscetibilidade do solo à compactação.

Crop residues may buffer part of compressive stress applied over the soil surface. Thus, indiscriminate crop residue removal would magnify soil compaction in highly mechanized cultivation systems, such as sugarcane in Brazil. Nevertheless, the effect of different amounts of sugarcane crop residue (straw) on soil compaction mitigation still needs to be tested. We conducted a laboratory study to quantify the effects of sugarcane straw rates on soil compaction indicators in response to external applied stress. The experiment involved remolded soil cores with four initial bulk densities: 1.25, 1.35, 1.45 and 1.55 Mg m−3, and five amounts of straw were left on soil surface, equivalent to 0, 5, 10, 15 and 20 Mg ha−1. The soil cores were subjected to uniaxial compression test and seven successive vertical static loads (25, 50, 100, 200, 400, 800 and 1600 kPa) were applied over the soil surface using a pneumatic consolidometer. Soil displacement was measured after each applied load. Based on these values, apparent precompression stress (σp), apparent compression index (CI) and final bulk density were calculated as indications of soil deformation. Because, soil inherent properties should not change, we call the changes due to straw layer addition "apparent" in this study. Our results revealed that large amounts (>10 Mg ha−1) of straw increased subtly apparent soil load bearing capacity (i.e., increased up to 15 kPa in apparent σp; 7%). The bulk density change rate (soil deformation) decreased due to presence of straw under low stress ( 400 kPa) levels in loose soil. On the other hand, compaction was slightly reduced in compacted soil, with corresponding reduction on apparent CI values. Nevertheless, despite this buffer effect provided straw, we noticed that increases in surface straw amount are likely insufficient to reduce the risk of compaction (little gain in apparent load-bearing capacity), but a reduction of about 5% on the soil deformation (as apparent σp is overcome) could occurs in compacted soils. We advocate that benefits of leaving sugarcane straw covering the soil go beyond the direct “damper” effect, because straw is source of carbon, which is fundamental for enhancing soil structure stability and biological activity, and thus, reducing soil compaction risks or even alleviating soil compaction restrictions to plant growth. Finally, we encourage future studies to test the straw effects under machinery traffic in field conditions, which could involve the additional effect of shear stress over the tyre-straw-soil interface.

Soil strength is not only affected by water content and bulk density, but also by the age-hardening phenomena, which plays a key role in increasing the soil strength as a function of time. It has been demonstrated that soil penetration resistance in no-tillage is higher when compared with other tillage systems at the same bulk density and water content. The objectives of this study was to investigate the effects of the age-hardening phenomena on soil penetration resistance in a long-term soil management system, running since 1988 in a very clayey Oxisol, in southern Brazil. Soil samples were collected from three soil layers (0.0–0.10 m; 0.10–0.20 m and 0.20–0.30 m) and five soil tillage systems: conventional tillage; minimum tillage with chiselling performed every year or every three years; and no-tillage for 11 or 24 years. Age-hardening was investigated using soil penetration resistance analysis and modelling. We used the area under the soil resistance to penetration curve to compare the age-hardening phenomena under the different tillage systems. For the same bulk density and water content, the soil resistance to penetration increased with time under no-tillage or without soil chiselling. For the same bulk density, no differences were found for macroporosity and microporosity among the tillage systems. Higher soil penetration resistance values in long-term no-tillage at the same soil bulk density and water content were attributed to the age-hardening phenomena, which increased the number and strength of bonds among soil particles, leading to higher soil cohesion. It is necessary to establish critical limits of soil penetration resistance as a function of the soil tillage system, and the time without soil chiselling or under no-tillage system.

Assessment and monitoring impacts of agricultural systems on soil quality are imperative to establish best management practices and sustainable land use for mitigating climate change, conserving biodiversity and achieving food and energy security. The SMAF has successfully been tested as an objective tool to quantify land use and management effects on soil quality, including under some Brazilian soil conditions. Nevertheless, the SMAF potential to properly address soil quality changes under contrasting soil and climate conditions, and integrated farming systems must still must be investigated. Thus, a field study was conducted to apply the SMAF guidelines as a strategy for assessing land use (native vegetation, pasture, sugarcane, no-tillage, and integrated crop-livestock systems) effects on soil quality in southern Brazil. Soil samples were taken in three layers (0.0–0.10, 0.10–0.20, 0.20–0.30 m) of clay Ferralsol (traditional agricultural region), Sandy loam Ferralsol and Arenosol (new agricultural frontiers), in the state of Parana, Brazil. The soil quality indicators investigated were: chemical attributes (pH, phosphorus and potassium), physical (bulk density) and biological (soil organic carbon). Using the SMAF scoring curves, the measured values were transformed (0 to 1 range) and an overall soil quality index (SQI) was calculated. Our findings revealed that long-term conversion from native vegetation to agricultural land uses (i.e., pasture, no-tillage/integrated crop-livestock system, or sugarcane) reduced soil quality assessed by SMAF scores, compromising the soil’s capacity to perform its functions. Nevertheless, conservationist systems, e.g. the no-tillage, associated or not with the integrated crop-livestock system are promising alternative to enhances soil quality by increasing C content and soil chemical fertility compared to degraded pasture or conventional sugarcane cultivation. However, soil physical changes should be monitored to alleviate soil compaction in no-tillage cropping systems. In conclusion, this study provided important insights about soil quality changes induced by land use and diversified cropping systems. In that direction, new studies including a large number of sites, soil types and cropping systems are needed for validating our conclusions in a regional scale, enabling to support decision-making towards more sustainable expansion and intensification of agriculture in Brazil.

Sustainability of crop production systems depends on the preservation of soil physical quality over time. This study aimed to determine long-term effects of soil tillage and cropping systems on physical attributes and hydraulic properties of an Oxisol in Southern Brazil, emphasising management practices to preserve or improve the soil structure quality under no-tillage system. The experiment was conducted in randomized block design, using a 5 × 2 factorial arrangement (tillage × cropping systems), with four replications. The five tillage systems consisted of conventional tillage (CT); minimum tillage, chiselled soil every year (MTC1); minimum tillage, chiselled soil every three years (MTC3); continuous no-tillage for 11 years (NT11); and continuous no-tillage for 24 years (NT24). The two cropping systems consisted of annual crop sequence with wheat in the winter and soybean in the summer, designated as crop succession (CS); and a 4-year crop rotation (CR) with white lupine-maize—black oat-soybean—wheat-soybean—wheat-soybean in winter–summer, respectively. Undisturbed soil cores were collected from 0–0.10; 0.10–0.20 and 0.20–0.30 m of soil depth, to determine the soil bulk density (BD), total porosity, macroporosity, microporosity, pore size distribution and classes, soil water retention curve, infiltration rate and field-saturated hydraulic conductivity. There was no interaction between tillage and cropping systems, and no effects of cropping systems on soil physical and hydraulic properties. Regardless the cropping system, chiselling effects on soil physical properties persisted for less than 22 months, and were restricted to below 0.20 m soil depth. The CT resulted in soil pulverization at 0–0.10 m depth, leading to lower BD and higher macroporosity compared to the other soil tillage systems. At layers below 0.10 m, CT increased the BD and reduced the macroporosity to critical levels for crop growth. Continuous use of no-tillage improved soil physical quality mainly at deeper layers, and provided higher plant available water retention in the soil at matric potentials ranging from −10 to −200 kPa in relation to CT and MTC1. The adoption of NT improves soil physical quality and plant available water over time, and periodic soil chiselling aiming to disrupt compacted layers should be avoided because of its effects on reducing soil compaction level are short-lived.

Estimation of soil load-bearing capacity from mathematical models that relate preconsolidation pressure (σp) to mechanical resistance to penetration (PR) and gravimetric soil water content (U) is important for defining strategies to prevent compaction of agricultural soils. Our objective was therefore to model the σp and compression index (CI) according to the PR (with an impact penetrometer in the field and a static penetrometer inserted at a constant rate in the laboratory) and U in a Rhodic Eutrudox. The experiment consisted of six treatments: no-tillage system (NT); NT with chiseling; and NT with additional compaction by combine traffic (passing 4, 8, 10, and 20 times). Soil bulk density, total porosity, PR (in field and laboratory measurements), U, σp, and CI values were determined in the 5.5-10.5 cm and 13.5-18.5 cm layers. Preconsolidation pressure (σp) and CI were modeled according to PR in different U. The σp increased and the CI decreased linearly with increases in the PR values. The correlations between σp and PR and PR and CI are influenced by U. From these correlations, the soil load-bearing capacity and compaction susceptibility can be estimated by PR readings evaluated in different U. A estimativa da capacidade de suporte de carga do solo a partir de modelos matemáticos que relacionam a pressão de preconsolidação (σp), a resistência mecânica do solo à penetração (RP) e o conteúdo gravimétrico de água do solo (U) é importante na definição de estratégias para prevenção da compactação de solos agrícolas. Portanto, objetivou-se modelar a σp e o índice de compressão (IC) em função da RP (em campo com penetrômetro de impacto e em laboratório com penetrômetro digital de bancada) e do U em um Latossolo Vermelho. O experimento foi composto por seis tratamentos: sistema plantio direto (SPD); SPD com escarificação; e SPD com compactação adicional pelo tráfego de uma colhedora por 4, 8, 10 e 20 passadas. Os valores de densidade do solo, porosidade total, RP (no campo e no laboratório), U, σp e IC foram determinados nas camadas de 5,5-10,5 cm e 13,5-18,5 cm. A modelagem da σp e do IC foi realizada em função da RP em diferentes U. A σp aumentou e o IC diminui linearmente com incremento nos valores de RP. As relações entre σp e RP e IC e RP são influenciadas pelo U. A partir dessas relações, é possível estimar a capacidade de suporte de carga e a suscetibilidade do solo à compactação por meio das leituras de RP, avaliadas em diferentes U.

A utilização de fontes não renováveis, para a produção de adubos minerais, causa grandes impactos ao meio ambiente. A redução desses impactos é favorecida pela crescente busca por novas fontes nutricionais orgânicas, para as culturas. Este trabalho objetivou avaliar a utilização de resíduo de indústria de carnes (RIC) como fonte alternativa de nutrientes para as culturas do girassol e milho. Foram utilizadas cinco doses de RIC (0 m³ ha-1, 25 m³ ha-1, 50 m³ ha-1, 75 m³ ha-1 e 100 m³ ha-1) e um tratamento com adubação mineral. O RIC proporcionou aumento na produtividade de grãos das culturas de girassol e milho. Na cultura do milho, a máxima produtividade foi obtida com a dose de 87 m³ ha-1 de RIC, equivalendo a 92% da produtividade obtida com a adubação mineral. Na cultura do girassol, doses iguais ou superiores a 20 m³ ha-1 de RIC proporcionaram produtividades iguais ou superiores às obtidas com adubação mineral. O RIC apresentou potencial agrícola para uso como fertilizante orgânico, podendo substituir, parcial ou totalmente, a adubação química. The use of non-renewable sources for the production of mineral fertilizers causes major impacts to the environment. The reduction of these impacts favors the increasing search for new organic nutrient sources for crops. This study aimed to evaluate the use of residue from meat industry (RMI) as an alternative source of nutrients for sunflower and maize crops. Five doses of RMI (0 m³ ha-1, 25 m³ ha-1, 50 m³ ha-1, 75 m³ ha-1 and 100 m³ ha-1) and one treatment with mineral fertilization were tested. The RMI provided an increase in grain yield for the sunflower and maize crops. In the maize crop, the highest yield was obtained with the dose of 87 m³ ha-1 of RMI, equivalent to 92% of the yield obtained with mineral fertilization. In the sunflower crop, doses equal to or higher than 20 m³ ha-1 of RMI provided equal or higher yields than those obtained with mineral fertilization. The RMI presented agricultural potential for use as an organic fertilizer and can partially or totally replace chemical fertilization.