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On the coastal plain of Rio Grande do Sul State, Brazil, the soil salinity is strictly related to the quality of irrigation water sources connected to the Atlantic Ocean, especially the Patos Lagun...

The insertion of the animal component into the crop production system can alter the nutrient dynamics and, consequently, the soil fertility status over time. This change occurs differently according to the arrangement adopted, depending on both, the intensity and frequency of animal grazing, as well as the crop rotation system. This study was carried out aiming to evaluate the effect of sheep grazing intensity and frequency during the winter period and the crop rotation in the summer period on the (i) temporal evolution and vertical distribution of soil chemical properties, and (ii) on the nutrient (phosphorus – P, potassium – K, calcium – Ca, and magnesium – Mg) budget. The experiment was established in 2003, in a subtropical Acrisol in southern Brazil, arranged in a randomized block design with split plots. The treatments were two grazing intensities (moderate and low), two stocking methods (continuous and rotational), subdivided into two crop rotation systems (monoculture - soybean/soybean and crop rotation soybean/maize). Temporal variation of soil pH, exchangeable aluminum (Al), Ca and Mg, available P and K, base saturation, Al saturation, and cation exchange capacity (CEC) were evaluated in samples collected in 2003, 2010, 2015 and 2017, corresponding to 0, 7, 12 and 14-years after the beginning of the experiment. The vertical distribution (0–5, 5–10, 10–20, 20–30 and 30–40 cm) of these chemical properties were also evaluated 14-years after the beginning of the experiment (2017). The nutrient budget in the soil was calculated based on the initial and final available/exchangeable contents in the 0–10 cm soil layer and the inputs (fertilizers) and outputs (exportation by grain and meat) of nutrients. >95% of P, K, Ca and Mg were exported by grains and

The conversion of Pampa Biome soils into no-till system for grain production requires acidity correction, at least to fully neutralize exchangeable aluminum (Al). The aim of the study is to...

No-tillage (NT) systems have arisen as a promising alternative to traditional rice cultivation in flooded soils, such as pre-germinated (PG) and conventional tillage (CT) systems. However, how NT affects soil properties and grain yield is not completely understood, especially over the long term. The objective of this study was to evaluate the long-term impact of three tillage systems (CT, NT and PG) on soil chemical, physical and biological attributes and the influence of these attributes on rice yield over time in a lowland soil of the Brazilian subtropical region. The rice grain yield was evaluated for 16 growing seasons, and the soil properties were evaluated from 17 to 21 years after the beginning of the experiment. After 14 growing seasons, rice yield was greater (3.4%) under the NT system compared to under the CT system. The increase in rice yield over time resulted in 67% greater soil organic matter (OM) content, exchangeable Ca and Mg and consequently cation exchange capacity (CEC) under the NT system compared to the CT and PG systems. In addition, soil bulk density and microbial C and N were 15%, 40% and 75% greater, respectively, under the NT system than under the CT system in the surface soil layer. The lack of soil disturbance associated with the high input of crop residues and flooding soil conditions favored the chemical, physical and biological soil properties through soil OM content, improving rice yields after 14 yr of NT adoption in relation to CT adoption.

Climate models project greater weather variability over the coming decades. High yielding systems that can maintain stable crop yields under variable environmental scenarios are critical to enhance food security. However, the effect of adding a trophic level (i.e. herbivores) on the long-term stability of agricultural systems is not well understood. We used a 16-year dataset from an integrated soybean-beef cattle experiment to measure the impacts of grazing on the stability of key crop, pasture, animal and whole-system outcomes. Treatments consisted of four grazing intensities (10, 20, 30 and 40 cm sward height) on mixed black oat (Avena strigosa) and Italian ryegrass (Lolium multiflorum) pastures and an ungrazed control. Stability of both human-digestible protein production and profitability increased at moderate to light grazing intensities, while over-intensification or absence of grazing decreased system stability. Grazing did not affect subsequent soybean yields but reduced the chance of crop failure and financial loss in unfavorable years. At both lighter and heavier grazing intensities, tradeoffs occurred between the stability of herbage production and animal live weight gains. We show that ecological intensification of specialized soybean systems using livestock integration can increase system stability and profitability, but the probability of win–win outcomes depends on management.

Studies that evaluate the crop responses to the soil modifications intermediated by gypsumapplication are relatively abundant, but most of them are performed in highlands. Such studies are still scarce in lowlands. The objective of our study was to evaluate soil acidity and phosphorus (P) and potassium (K) availability, as well as crop (irrigated rice and soybean) yields, as a function of different rates of gypsum application in lowland. The experiments were conducted in a Planosol (Triunfo, Rio Grande do Sul, Brazil). The treatments consisted of six gypsum rates (0.00, 0.25, 0.50, 1.00, 2.00 and 4.00 t ha-1) and the experimental design was in randomized blocks with four replications. The soil was sampled after crop harvests, in the 0–5, 5–10, 10–20 and 20–40 cm layers. The soil pH (in water), the potential acidity (H+Al) and the available P (Mehlich 1) were not affected by gypsum application. After the irrigated rice cropping and in the soil layer of 0–5 cm, the available K (Mehlich 1) contents was impacted by the gypsum application, with increase in content for rates up to 1.00 t ha-1 and decrease in content for higher rates (2.00 and 4.00 t ha-1). After the soybean cropping, the available K content was not affected by gypsum application. The gypsum application did not impact irrigated rice and soybean yields in the evaluated season, which did not present water deficit.

In subtropical lowlands, the introduction of soybean and livestock in rotation are an alternative to rice monoculture. Due to the nutrient cycling process improved by animal grazing in winter fertilized pastures, soybean may not respond to mineral fertilization under a no-till integrated crop&ndash, livestock system (ICLS). Thus, the objectives of this study were to evaluate (i) the soybean yield response to different fertilization levels of phosphorus (P) and potassium (K) and (ii) the relationship between soybean yield and soil chemical properties sampled in different soil layers, in a no-till ICLS in subtropical lowlands. Two field studies were conducted in a system that included a soybean-flooded rice rotation integrated with cattle grazing during the winter season. During the 2015/2016 cropping season, five levels of P and K fertilization were applied to the soil. During the 2017/2018 cropping season, the relationships between soybean yield and soil chemical properties were evaluated under no fertilization treatment. Soybean yield under an ICLS did not respond to P and K fertilization, even when the soil P level was below the critical threshold. The associations between soybean yield and soil chemical properties were greatest in the 10&ndash, 20 cm soil layer as compared with the 0&ndash, 10 cm soil layer, especially for available P, followed by pH and soil organic matter (SOM). The crop rotation and ICLS adoption under no-till reduced the soybean reliance for mineral fertilization prior to cropping. Results of this study inform producers of possible fertilization adjustments, in which supplementing mineral fertilizer for soybean may not be necessary.

Managing for resilience in agriculture will be required to overcome future challenges such as growing food demand, climatic uncertainty, scarce raw materials and economic instability. Identifying resilience-enhancing practices is therefore fundamental for developing sustainable agroecosystems. We aimed to assess the resilience of two agricultural systems with different levels of diversification in southern Brazil: a specialized soybean (Glycine max) system and an integrated soybean-beef cattle system. We assessed the robustness and the adaptive capacity of these systems when facing climate hazards and price volatility. The study was based on a long-term trial that has been carried out since 2001, composed of an annual rotation of no-till soybean production during the summer and grazing of mixed black oat (Avena strigosa) and Italian ryegrass (Lolium multiflorum) pasture in the winter. Treatments consisted of four grazing intensities in the integrated crop-livestock system (ICLS), defined by sward heights: 10, 20, 30 and 40 cm plus an ungrazed control representing the specialized cropping system (CS). The experiment was carried out using a randomized complete block design with three replicates. We analysed system results over five years using two methods: i) a downside risk analysis to estimate the expected losses of yield and gross value added; and ii) the Ecological Network Analysis, which was applied to each treatment and year, for the assessment of the resilience of nitrogen (N-Ɍflow) and phosphorus (P-Ɍflow) flows. Both methods showed that co-located crop-livestock production in an ICLS was more resilient than the specialized soybean system and had improved nutrient cycling and resource-use efficiency. The effects of grazing management on system resilience depended on the output: beef yields were more stable under lower grazing intensities, but the risk of falling below a target economic threshold was inversely proportional to grazing intensity and null when the highest grazing intensity was adopted. The ecological network analysis did not reveal differences in resilience of nutrient flows among grazing management treatments. Our study suggests that Ɍflow (N or P) is a useful proxy for assessing the robustness and adaptability of agroecosystems. Our comprehensive resilience analysis of nutrient and economic flows provides evidence that system diversification through the integration of grazing animals into specialized cropping systems is a good strategy towards the sustainable intensification of agriculture. It would be relevant, however, to consider further studies comparing more complex system configurations and levels of diversification.

Lowland soils represent 4 to 6% of the earth's surface, covering an area of 7 to 9 million km2. Most of these areas can be used for flooded rice cultivation, as a paddy field. These soils commonly have low fertility due to the traditional flooded rice cultivation systems, which are based on intensive soil tillage and rice monocropping. On the other hand, soil conservation management systems, such as no-tillage and integrated crop-livestock systems (ICLS) may increase the soil fertility and consequently improve rice yield. In lowlands, these practices are contributing to sustainable soil management. Therefore, our study aimed to evaluate soil fertility properties by measuring soil organic matter (SOM) and soil available phosphorus (P) and potassium (K) contents, five years after the adoption of different paddy-farming systems in an Albaqualf soil. The long-term ICLS experiment is located in Cristal county, Rio Grande do Sul State, in Southern Brazil. The systems consisted of two ICLS under no-tillage (NT), in comparison to the traditional system (S1) of flooded rice cultivation under soil disturbance, rice monocropping, and winter fallow. The ICLS systems were based in: rice cultivation in summer season and pasture (annual ryegrass) with cattle grazing in winter season (S2), and crop rotation (rice and soybean) in summer season and livestock production in winter season (S3). In 2013, at the beginning of the experiment, and after five years (2018), soil samples were collected in the 0–10 and 10–20 cm layers, and then the SOM, and available P and K contents were analyzed. Regarding the rice yield, S2 and S3 always had higher rice yields than S1. The S2 and S3 showed increases in yields of 8.9 and 16.4% in relation to S1, with average yields of 11.3 and 12.1 Mg ha-1, respectively. In addition to S3 having the highest rice yields, it also had high soybean yields for lowland environment in the period evaluated, with an average of 3.8 Mg ha-1. After five years, S2 and S3 increased SOM contents by 27% and 50%, respectively, in the 0–20 cm soil layer. Similar behavior was verified in available P, with decrease of 4.6 mg dm-3 in S1 and increase of 16.0 mg dm-3 in the S3 compared to the initial evaluation. The available K content was higher in S3 (79.3 mg dm-3), followed by S2 (68.1 mg dm-3) and S1 (59.5 mg dm-3) on average of two years evaluated, in the 0–10 cm soil layer. Therefore, the results shows that NT adoption, combined with crop rotation and ICLS, improve soil fertility attributes, which results in high rice yields over time, reaching the sustainable intensification of lowlands.

An integrated crop-livestock system (ICLS) under no-till may be an effective tool to promote soil organic carbon (SOC) accumulation. However, it is not yet clear how pasture management affects SOC accumulation. In this study, we assessed the effect of grazing intensity (10, 20, 30, and 40 cm of sward height and no grazing) on SOC and coefficients of soil organic matter dynamics and used them in a simulation of SOC sequestration in a 0-20 cm soil layer. The overall study was conducted on a subtropical rhodic hapludox from southern Brazil managed as a no-till integrated soybean-beef cattle system for 13 yr. SOC sequestration rates ranged from 0.097 Mg ha?1 yr?1 with a pasture sward height of 10 cm to 0.308 Mg ha?1 yr?1 with one of 40 cm. Simulations revealed a higher potential of the soil for C sequestration with a moderate (30 cm) or low (40 cm) grazing intensity. Although the ICLS under no-till led to a positive carbon balance irrespective of grazing intensity, the simulation of temporal evolution of SOC stocks over time revealed a higher potential for SOC accumulation with the less intensive grazing treatments than with the more intensive ones.

Diversified farming systems is a challenge in lowland soils around the world. In Southern Brazil, integrated crop-livestock systems (ICLS) have been used for grain crops and livestock production under no-till. However, their impacts on soil K dynamics are still poorly explored. The aim of this study was to quantify the K forms in the soil and the K budget after 66 months of different flooded rice production systems under no-till ICLS in a subtropical paddy field. Four production systems were established in 2013: (i) flooded rice monocropping under conventional tillage (CT) and winter fallow (R-CT); (ii) no-tillage (NT) flooded rice monocropping with ryegrass pasture in winter (R-ICLS); (iii) NT flooded rice and soybean rotation in the summer and ryegrass pasture in winter (RS-ICLS), and (iv) NT flooded rice, soybean, maize and stapf grass rotation in the summer period and ryegrass and clover pasture in the winter (RSM-ICLS). In 2018, soil samples were taken at the 0–10, 10–20 and 20–30 cm soil layers. Exchangeable potassium (K), non-exchangeable K, structural K, and total K were evaluated. Exchangeable K was not affected by the treatments. The higher the difference between inputs and outputs of K in the systems evaluated, the higher was the content of structural and total K in the soil. However, the K budget in the system was not sufficient to fully explain the variation in the non-exchangeable K content in the soil. Comparing the systems with the same frequency of flooded rice cultivation, the difference between inputs and outputs of K was about 2.3 times higher in the R-ICLS system (830 kg ha−1 of K) compared to R-CT (366 kg ha−1), which increase in 70 % the concentration of non-exchangeable K in the 0–30 cm soil layer (622 and 361 mg kg−1 in the R-ICLS and R-CT, respectively). In the systems where flooded rice rotates with rainfed crops (RS-ICLS and RSM-ICLS), the drying cycles resulted in K fixation with higher energy, turning the surplus of K added via fertilization into structural forms. These results indicate that lowland soils cultivated with K fertilization rates greater than the export of K can result in a fixation of K, decreasing its availability in the short-medium term. Moreover, it strongly emphasizes that adequate K fertilization in lowland soils with 2:1 clayminerals should focus on the reposition of exported K in order to prevent temporary fixation of K by fixation on structural forms.

International audience; AbstractCommercial-scale integrated crop-livestock systems intensify land use by combining complementary agricultural enterprises and leveraging synergistic ecosystem services to achieve both productive and environmental outcomes. Although widely implemented in southern Brazil as an annual beef/soybean rotation, tradeoffs such as competing soil water use between pasture and crop phases may result from seasonal grazing in this system. We compared soil water and plant physiological variables in the crop phase of an integrated annual beef-soybean system managed with no-till and best grazing practices with those of an ungrazed cover crop control as part of a long-term experiment in southern Brazil. A mixed black oat (Avena strigosa Schreb.) and Italian ryegrass (Lolium multiflorum Lam.) pasture was either grazed by beef cattle to 20-cm sward height or left as an ungrazed cover crop in the winter, and direct-planted to soybean (Glycine max [L.] Merr.) in the summer. Although soybean yields did not differ between grazed and ungrazed treatments, soil matric potential was on average 25% lower across depths and growth stages in plots that had been grazed during winter. Soybeans in grazed plots also exhibited up to 34% lower light-use efficiency and a 2-week slower time to physiological maturation than soybeans in plots that had not been previously grazed. These results describe for the first time the differential crop growing conditions and crop physiological responses created after 16 years of integration with grazing animals. As integrated crop-livestock systems grow in importance in commercial production settings, this research can inform adaptive management practices to ensure the sustainability of these systems into the future and under a variety of environmental conditions.

The presence of animal grazing at different intensities in integrated crop livestock systems (ICLS) may affect the forms and the balance of K in the soil, especially after many years. The objective of this study was to evaluate different K forms and their balance for 17 years with ICLS. ICLS experimental area used no-till practices with different grazing intensities of cattle in winter pasture (black oat + annual ryegrass) and soybean production in the summer season. The experiment started in May 2001 at a location with a Rhodic Hapludox (Oxisol). The treatments consisted of varied grazing intensities: intensive grazing (IG) at 10 cm of pasture height, moderate grazing (MG) at 20 cm of pasture height, and a no grazing (NG) treatment. The experimental design was a randomized block design with three replicates. Soil samples were collected in 2001, 2007, 2012 and 2017 in 0−5, 5−10, 10−15 and 15−20 cm of soil layers. Desorption of K was measured using the Mehlich-1 method and the results were fitted to first-order kinetic equations to obtain readily and potentially available K content. Total K was determined by X-ray fluorescence, and the unavailable K by the difference between the total K and potentially available K. Long-term no-till ICLS resulted in an increase in more readily available K forms in the soil surface. The increase was especially prominent in the no-grazing treatment due to the greater amount of K left in the plant residues. Regardless of grazing intensity, soybean cultivation was the controlling component of the soil nutrient budget, representing 98.6 % of the total amount of K exported. Animal outputs represent only 1.4 % of total K exported and are therefore the recycling component of the system. Although meat production in ICLS represents only a very small fraction of the amount of K exported from the system, K tends to become less available in the grazed treatments in the long-term.

No-till, crop diversity and integrated crop-livestock systems are proposed managements to increase agriculture sustainability in the rice paddies of the Southern Brazilian lowlands and avoid degradation in the region. Since soil is considered a key medium in which management modifications can be measured, our study aimed to evaluate soil-quality impacts by measuring carbon and nitrogen stocks and microbial activity 18 months after the adoption of different paddy-farming systems in an Albaqualf soil of Southern Brazil. The treatments consisted of 5 paddy-farming systems with a range of vegetation diversity (both in time and space) and grazing seasons. In addition, a reference area (i.e., native forest) was sampled for comparison. We verified that soil quality was affected over the short term through the adoption of no-till, crop diversity, and integrated grazing practices. However, during the study period, only the system with low anthropic and/or mechanical intervention and high plant diversity differed from the traditional paddy land-use approach in Brazil in terms of soil-quality effects. This system achieved a carbon management index of 49 (approximately half that of the native forest) and had the highest enzymatic activity (similar to native forest). These outcomes were primarily due to an increase in the particulate organic matter fraction of the soil carbon stock (4.6 Mg ha-1 more than in rice monocropping). To evaluate changes in soil quality over the long term, additional studies are required.

The water availability is the main limiting factor of global rice production under flood irrigation. In this context, water suppression during the rice growing cycle (intermittent irrigation) arises as an alternative to traditional continuous irrigation. However, the intermittent irrigation may affect the dynamics of soil solution chemical attributes, the water use and the rice yield. Thus, our study aims to evaluate the electrochemical characteristics and nutrient availability in soil solution during the growing cycle, the plant response and the water use efficiency of irrigated rice under different flood irrigation management methods. For this, a field experiment was conducted in Southern Brazil, with three treatments: 1) continuous irrigation; 2) one water suppression (between V6–V8); and 3) two water suppressions (between V6–V8 and V8–V10). Regarding soil solution electrochemistry, the pH and redox potential (EH) were affected by the water suppression, increasing and decreasing due to soil reoxidation, respectively. The electrical conductivity (EC) decreased during the rice growing cycle, accompanying the plant development. The nutrients (except the potassium) were affected by water suppression, diminishing their availability. However, when the water layer was reestablished, there were no differences on soil solution electrochemistry among the irrigation methods. Regarding rice response, no differences were observed and the amounts produced were, in average, 9.9 and 13.4 Mg ha−1 of grains and shoot dry matter, respectively. The same occurred for the water amount utilized and water use efficiency (WUE) and the values observed were, in average, 9094 m3 ha−1 and 1.1 kg m−3, respectively. More studies regarding different flood irrigation management methods are necessary to encourage the adoption of intermittent irrigation by rice farmers of Southern Brazil and increase the sustainability of rice production.

The objective of this work was to evaluate the impact of grazing intensities after 11 years of an integrated crop-livestock system, under no-tillage, on soil moisture and soybean physiological parameters during a summer season affected by drought. The experiment was established in 2001 on a Rhodic Hapludox. Treatments consisted in the succession of soybean (summer) and a mixed pasture of black oat + Italian ryegrass (winter), under different beef-cattle grazing intensities: intensive grazing, with 0.10-m pasture height; moderate grazing, with 0.20-m pasture height; and no grazing. During the soybean cycle, in the 2011/2012 crop season, rainfall was 40% of the climatological normal. The soil moisture was within the limits of available water both under moderate grazing and no grazing, at 0.00-0.50-m soil depth, but, under intensive grazing, it was below the permanent wilting point, especially up to the grazing height of 0.20 m. Intensive grazing affected negatively the plant physiology parameters, reaching peaks of -2.5 MPa and +6°C for leaf water potential and leaf-air temperature difference, respectively. Moderate grazing or the absence of grazing, during the winter season, results in similar physiological responses, contributing to soybean plant homeostasis. Resumo: O objetivo deste trabalho foi avaliar o impacto de intensidades de pastejo após 11 anos de um sistema de integração lavoura-pecuária, em plantio direto, na umidade do solo e em parâmetros fisiológicos da soja durante uma safra de verão afetada por seca. O experimento foi iniciado em 2001, em um Latossolo Vermelho. Os tratamentos consistiram na sucessão de soja (verão) e pastagem mista de aveia-preta + azevém (inverno), com diferentes intensidades de pastejo por bovino de corte: pastejo intensivo, com altura de pastejo de 0,10 m; pastejo moderado, com altura de pastejo de 0,20 m; e sem pastejo. No ciclo da soja, na safra 2011/2012, a precipitação foi de 40% da normal climatológica. A umidade do solo ficou dentro dos limites de água disponível, tanto em pastejo moderado quanto sem pastejo, na camada de 0,00-0,50 m, mas, em pastejo intensivo, a umidade do solo foi menor que o ponto de murcha permanente, especialmente até 0,20 m de altura de pastejo. O pastejo intensivo afetou negativamente os parâmetros fisiológicos da soja, que atingiu picos de -2.5 MPa e +6°C para potencial de água na folha e diferença entre temperatura do ar e da folha, respectivamente. O pastejo moderado ou a ausência de pastejo, durante o inverno, acarreta respostas fisiológicas similares, o que contribui para a homeostase da soja.

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.

Integrated crop-livestock systems (ICLS) conducted under no-tillage have been shown to favour the accumulation of carbon (C) and nitrogen (N) in soil. In that systems, however, C and N accumulation in soil might depend on pasture management and the type of crop rotation used. The objective of this study was to evaluate the impact of two stocking methods (continuous and rotational) and two sheep grazing intensities (moderate and low) on winter pasture and the effect of summer crop rotation (soybean and/or maize) on crop yield and C and N stocks in an Acrisol after 14-yr under experimental conditions. The evaluated ICLS was set up for grain yield in the summer crop phase and for sheep meat production in the winter pasture phase. Pasture production, soybean and corn yield were evaluated throughout the experimental period. After 14-yr, the soil was sampled at the 0–5, 5–10, 10–20 and 20−30 cm layers to evaluate the content and stock of C and N. Higher C and N contents in soil superficial layers (0–5 and 5–10 cm) were observed under low grazing intensity in winter and soybean monoculture in summer. The C and N stocks in 0−30 cm soil layer ranged between 39 and 45 Mg C ha−1 and 4 and 5 Mg N ha−1, respectively. C and N stocks in the soil were significantly related to N added through the residues of pasture and summer crop. This positive relationship is possibly explained by the higher efficiency of microbes in using crop residues enriched in N with posterior stabilization of microbial residues through organo-mineral association in the soil. The higher content and stocks of C and N associated with low intensity grazing favoured a higher maize yield (40%) compared to moderate grazing intensity in the 2015/2016 season. According to our results, the accumulation of C and N in the soil under ICLS involving low grazing intensity in the winter and soybean monoculture in the summer was related to the N added/recycled by the soybean and by the hibernal pasture.

Integrated crop-livestock systems (ICLS) can be an option for agricultural sustainability in subtropics. Despite numerous studies evaluating ICLS, there have been limited investigations of aluminum (Al) dynamics in such systems. In this context, this study was conducted in 2001–2010 on Rhodic Hapludox soil with the objective of assessing the impacts of time and grazing on soil acidity and Al fractions (solid phase) and species (liquid phase) in ICLS (soybean-beef cattle) managed with a long-term no-till system. The crop succession consisted of soybean cultivation during summer and a mix of black oat + Italian ryegrass during winter. Treatments consisted of different grazing managements during the winter season: intensive grazing, moderate grazing, and no-grazing. For this study, sampling was performed prior to the first and after nine grazing seasons. Lime was applied to the surface of the entire study area immediately after the first grazing season. We demonstrated differences in the Al forms in the soil solid and liquid phases over time and with different managements. The ICLS with intensive grazing or moderate grazing during the winter season led to a lower availability of total Al in the soil solution and a higher base saturation and lower Al saturation in the soil solid phase compared to non-grazed areas. However, the soil pH is similar between grazed and non-grazed. Despite such differentiated dynamics, the carbon accumulated in the soil with a long-term no-till management guarantees that the preponderant Al form is linked to organic compounds, maintaining the content of phytotoxic species and the Al3+ activity below the critical limit for plant growth.

The use of gypsum to improve the root environment in tropical soils in the southeastern and central-western regions of Brazil is a widespread practice with well-established recommendation criteria. However, only recently gypsum began to be used on subtropical soils in South of Brazil, so available knowledge of its effect on crop yield is incipient and mainly for soils under no-till (NT) systems. Avaiable studies span a wide range of responses, from a substantial increase to a slight reduction in crop yield. Also, the specific conditions leading to a favorable effect of gypsum application on crop yield are yet to be accurately identified. The primary objectives of this study were to examine previously reported results to assess the likelihood of a crop response to gypsum and to develop useful recommendation criteria for gypsum application to subtropical soils under NT in Brazil. For this purpose, we examined the results of a total of 73 growing seasons, reported in 20 different scientific publications that assessed grain yield as a function of gypsum rates. Four different scenarios were examined, by the occurrence or not of high subsurface acidity (viz., Al saturation >20 % and/or exchangeable Ca 3 cmolc dm-3) failed to increase crop yield, irrespective of the soil water status. Under these conditions, high gypsum rates (6-15 Mg ha−1) may even reduce grain yield, possibly by inducing K and Mg deficiency. On the other hand, applying gypsum to soils with high subsurface acidity increased yield by 16 % in corn (87 % of cases) and by 19 % in winter cereals (83 % of cases), whether or not the soil was water-deficient. By contrast, soybean yield was only increased by gypsum applied in the simultaneous presence of high soil subsurface acidity and water deficiency (average increase 27 %, 100 % of cases).

An integrated crop-livestock system (ICLS), with summer grain cropping and winter grazing of cover crops, is an option for agricultural management in subtropical areas. Despite numerous studies evaluating ICLS, there have been limited investigations of soil acidity and lime application dynamics in such systems. Because grain producers resist introducing livestock into cultivation areas due to fear of negative impacts of grazing on soybean yields and lime movement thorough the soil profile, the objective of this research is to evaluate the impacts of surface lime reapplication on the amelioration of soil acidity attributes and the yield of soybean in a long-term integrated soybean-beef cattle system under no-till under varying grazing intensities. An experiment was established in 2001 for an ICLS on a Rhodic Hapludox soil. Crop succession consisted of soybean ( Glycine max ) cultivation during summer and a mix of black-oat ( Avena strigosa ) + Italian ryegrass ( Lolium multiflorum ) during winter. Treatments consisted of varying grazing intensities during winter: intensive grazing, moderate grazing, and no-grazing. Lime was applied to the surface of the entire area at the beginning of the experiment, and a reapplication was performed nine years later (May of 2010) in a sub-parcel scheme (with and without lime reapplication). Soil acidity attributes (pH, base saturation and aluminum saturation) were evaluated at 12, 18, 24, and 30 months after lime reapplication, and the soybean yields of the 2010/11, 2011/12, and 2012/13 seasons were measured. As previously observed for the first surface lime application performed in the same trial area, the present study demonstrated that ICLS, regardless of grazing intensity, did not inhibit soil improvement in deeper layers after surface lime reapplication. In fact, the presence of animals helps to ameliorate soil acidity in deeper layers, compared to non-grazed areas. The soybean yield was not correlated with the soil acidity attributes and was affected by lime reapplication only under intensive grazing and drought conditions. However, when summer rainfall was lower than the expected climatological normal, soybean yields were higher in non-grazed areas.

Under integrated crop–livestock production system (ICLS), the animal acts as a catalyzer, modifying and accelerating fluxes by ingesting forage nutrients (grazing) and returning them to the soil as urine and dung in a continuous process whose magnitude and direction depend on grazing intensity. Thus, ICLS may change soil acidification processes and rates. The objective of this research was to verify the influence of grazing intensities on soil acidification through measurements of the soil chemical attributes in the soil profile and the efficiency of basic cation use in a soybean–beef cattle integration system nine years after surface liming under long-term no-till conditions in southern Brazil. An experiment established in 2001 in a Rhodic Hapludox with soybean (summer) and a mix of black oat + Italian ryegrass (winter) succession was used. Treatments consisted of different grazing intensities during the winter season: intensive grazing (IG), moderate grazing (MG), and no-grazing (NG). The experiment was set up in a randomized complete blocks design with three replicates. To evaluate soil chemical attributes, soil was sampled up to 40 cm, in May 2010, nine years after lime application. To quantify basic cations budgets and efficiencies, the inputs and outputs of calcium, magnesium, and potassium, as well as their initial and final exchangeable soil stocks were evaluated. Areas under grazed treatments, regardless of the intensity (IG or MG), presented lower soil acidification. Calcium and magnesium budgets were negative under NG and positive under MG. Potassium budgets were always negative, regardless of the management system, due to soybean grain harvest exportation and non-productive outputs. The soybean–beef cattle integrated system, with either IG or MG, was more efficient in calcium and magnesium utilization to produce protein; however, grazing does not affect potassium use efficiency.

Many investigations have focused in defining soil quality indicator components. However, for understanding better the impact of soil tillage systems on soil quality, a broader approach is demanded, with simultaneous soil attributes evaluations, by using multivariate analysis. The objective of this experiment was to evaluate the long-term effect of two tillage systems on the soil C and N stocks in comparison to those of native grassland and to identify the most suitable soil attributes for characterizing soil quality. The experiment was established in 1988 at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, Southern Brazil. Treatments consisted of two tillage systems (no-tillage and conventional tillage) and a reference area under native grassland. Soil analysis was performed up to 20 cm. Soil organic matter, C and N, physical fractionation was performed and carbon management index calculated. Microbial biomass C and N was determined as well as soil aggregate stability. From soil aggregation, soil average diameters and mass were grouped, and classes determined to calculate mean weight diameter. After 18 years, conventionally tilled soil showed lower total C and N stocks in comparison to no-tilled soil, which did not differ from native grassland soil. Soil C stocks ranged from 44.3 to 34.1 Mg ha−1 for the native grassland and conventional tillage system and total nitrogen ranged from 5.2 to 4.1 Mg ha−1 for the native grassland and no-tillage system, in the 0–20 cm layer. Among the tested soil quality indicators, the microbial biomass-C, total and particulate C stocks, particulate C and N stocks, and mean weight diameter were the indexes that best indicated soil tillage system effects, and they are therefore recommended for future use in evaluating soil quality.

Managing grazing stocks in integrated crop–livestock (ICL) systems under no-tillage is a key variable for reaching equilibrium in soil C and N budgets. Understanding how different plant and animal residues affect soil C and N stocks in these systems goes beyond soil dynamics since these elements are crucial for the functioning of the soil–plant–atmosphere system. The objective of this research was to determine soil C and N fractions, stocks, budgets and the carbon management index as affected by nine years of ICL with grazing intensities under no-tillage conditions. The experiment established in May 2001 in a Rhodic Hapludult (Oxisol) of southern Brazil was composed of black oat ( Avena sativa ) plus ryegrass ( Lolium multiflorum ) pasture in winter and soybean ( Glycine max ) crop in summer. Treatments were regulated by grazing pressures to maintain forage at 10, 20, 30 and 40 cm high (G10, G20, G30 and G40, respectively). Non-grazed (NG) treatment was the control. Changes in soil C and N stocks and fractions (particulate and mineral-associated) were assessed in the ninth year of the experiment. Moderate and light grazing intensities (G20, G30 and G40) resulted in similar increases in total organic C, particulate organic C, total N, and particulate organic N compared with NG treatment. Soil C additions ranged from 0.54 to 8.68 Mg ha −1 from NG to the other grazing treatments. The G10 led to a soil N loss of 1.17 Mg ha −1 due to soil organic matter degradation. The carbon management index (CMI) values, compared with native forest (NF) as a reference, indicated soil quality loss and degradation under high grazing intensity (G10). For a positive contribution to the soil system, ICL must be managed with moderate grazing intensities and adjustment of N additions through N fixation or fertilization.

Irrigated rice in the state of Rio Grande do Sul (Brazil) has shown significant growth in yield in recent years due to improved management practices, especially in regard to fertilizer use. However, the response curves that led to the current fertilizer recommendations do not consider integrated systems prevailing in rice-producing regions that have adopted the practice of integrated crop-livestock systems. The aim of the present study was to evaluate the effectiveness of current fertilizer recommendations for irrigated rice in lowland soils in Rio Grande do Sul under integrated crop-livestock systems for different periods of time. The experiments were performed in the 2012/2013 growing season on four farms in the state with different forage species under cattle grazing. In these areas, fertilizer recommendations were made based on previous soil analyses, and treatments consisted of fractions of the currently recommended application rates. At the end of the crop cycle, the percentages of maximum technical efficiency (PMTE) and maximum economic efficiency (PMEE) of NPK fertilizers, and increases in yield and net income provided by PMEE were determined. Rice yield increased and fertilizer response decreased over time in a rice-beef cattle integrated system. The highest incomes with fertilization of irrigated rice occurred at lower application rates than those recommended by soil analysis.

Sustainable intensification of land-use practices has never been more important to ensure food security for a growing world population. When combined under thoughtful management, cover cropping and crop-livestock integration under no-till systems can benefit from unexpected synergies due to their unique features of plant-animal diversification and complex agroecosystem functions. Mimicking the nutrient coupling/decoupling processes of natural ecosystems by diversifying plant and animal components of no-till integrated crop-livestock operations is an essential feature of the design of agroecological systems that support self-regulating feedbacks and lend resilience while increasing productivity and ecosystem service provision. Focusing on grazing animals as drivers of agroecosystem change, we highlight the benefits of grazed cover crops in rotation with cash crops for primary and secondary production and for soil physical, chemical, and biological parameters. However, careful management of grazing intensity is imperative; overgrazing drives soil deterioration, while light to moderate grazing enhances overall system functioning and allows for the generation of emergent properties.

In Rio Grande do Sul (RS) State, Brazil, the soils are not prone to salinization due to the large amounts of rainfall, which are sufficient to leach the soluble salts. However, flooded rice crops grown in the coastal plains of RS may be affected by soil salinity, once the soils in this region are formed by marine, fluvial-lacustrine sediments. The use of water for irrigation of crops from sources connected with the Atlantic Ocean, especially Patos Lagoon, can lead to deposition of excessive amounts of sodium in the soil, especially in southern portion, by the proximity to channel linking the lagoon to the sea. This study aimed to map the occurrence of salt-affected soils in the coastal plains of RS State, Brazil. The study was performed in three regions: Internal Coastal Plain (ICP), External Coastal Plain (ECP) to Patos Lagoon and North Shore. 766 georreferenced soil samples were collected and levels of exchangeable sodium, exchangeable sodium percentage (ESP) and electrical conductivity (EC) of saturated extract (ECse) were analyzed. The resulting analytical data of the sampling points were submitted to a descriptive statistic and used to generate maps aiming to depict the continuous spatial variation of each measured variable. Most of soil samples showed indicators of low soil salinity, especially in most of the ICP and North Shore. The soils most affected are concentrated in regions overlapping the paleochannels sub-surface previously identified in the sub-surface of the ECP and in areas closer to links between sources of freshwater and sea. In the ICP, the salinity problem was restricted to only some areas due to the use of saline water from Patos Lagoon.

The distribution of phosphorus in the soil profile as a function of soil tillage, fertilizer management system and cultivation time is strongly related to root distribution. As the dynamics of this process are not well understood, long-term experiments are useful to clarify the cumulative effect through time. The study evaluated an 18-year-old experiment carried out on Rhodic Paleudult soil, located in Rio Grande do Sul state – Brazil, with cover crops (black oat and vetch) in the winter and corn in the summer. In the 0- to 20-cm layer, the amounts of clay, silt and sand were 22, 14, and 64 g kg−1, respectively. This layer had a mean slope of 3%. The mean local annual rainfall is 1440 mm. The climate is subtropical with a warm humid summer (Cfa), according to the Koeppen classification. The treatments consisted of three soil managements (conventional tillage, no tillage and strip tillage) and three application modes (broadcast, row and strip) for triple superphosphate and potassium chloride fertilizers. Data for phosphorus and root distribution in the soil from the 1989/90, 1999/00 and 2006/07 growing seasons were used. Phosphorus stratification occurred through time, irrespective of soil and fertilizer management, mainly in the 0- to 5-cm layer. The tillage and fertilization systems promoted significant differences in the Pi and Pt fractions up to a depth of 20 cm. For the Po fraction, significant differences were found only in the 0- to 5- and 15- to 20-cm layers. Inorganic phosphorus accumulated in the fertilized zone (0–10 cm), with higher intensity in the no-tillage system under row fertilization with values around 150 mg dm−3. Root distribution presented a strong positive relationship with phosphorus distribution, exhibiting redistribution in the soil profile through time. This redistribution was accompanied by increases in organic phosphorus and total organic carbon content. Corn grain yield was not affected by long-term tillage systems.

A ciclagem e balanço de nutrientes em sistemas de integração lavoura-pecuária (ILP) são processos que envolvem o componente solo, a planta e o animal, além da fertilização, em que o manejo dos animais, por alterar as condições bióticas e abióticas do solo, altera a velocidade de decomposição dos resíduos. Objetivou-se avaliar a ciclagem e o balanço de K em sistema ILP sob semeadura direta, em função da intensidade de pastejo por bovinos em pastagem, no inverno, e sua relação com a produtividade de soja, cultivada no verão. O experimento foi iniciado em maio de 2001 em Latossolo Vermelho distroférrico, em área que vinha sendo cultivada em semeadura direta desde 1991. Os tratamentos constaram de intensidades de pastejo contínuo, por bovinos jovens, em mistura de azevém + aveia-preta, representados por alturas do pasto: 10, 20, 30 e 40 cm e sem pastejo (testemunha), distribuídos num delineamento experimental de blocos ao acaso, com três repetições, em que se avaliou um ciclo pastagem/soja (safra 2007/08). Na ciclagem, foram considerados os teores de K na pastagem, na soja e nos animais e, no balanço desse nutriente, na lavoura e no solo, foram considerados os seus teores no solo e as entradas, como fertilizante e saídas, nos grãos de soja e no tecido animal. A ciclagem do K aumentou com o aumento da intensidade de pastejo, e o seu balanço no sistema, apesar de negativo, com maior déficit nas áreas com maior intensidade de pastejo, não influenciou a produtividade da soja. Nutrient cycling and balance in integrated crop-livestock systems (ICL) are processes that involves soil, plant and animal components, beyond fertilization. Animal management, by modifying soil biotic and abiotic conditions, also influences this process as it affects the residue decomposition rate. The objective was to evaluate potassium (K) cycling and balance in an ICL system with grazing (black oat and ryegrass) intensities in the winter, followed by soybean cultivated in the summer. The experiment was conducted as of May of 2001 in an area in the state of Rio Grande do Sul – Brazil, on a Rhodic Hapludox (Oxisol), under no tillage since 1991. The treatments consisted of continuous bovine grazing intensities at a pasture height of 10, 20, 30 and 40 cm, and a control (no-grazing), in a randomized block design, with three replicates. The forage/soybean cycle of 2007/08 was evaluated in this paper. To calculate K cycling, the contents accumulated in pasture, soybean and animals in one pasture-soybean cycle were considered, and the balance, "in the field" and "in the soil", of K inputs (fertilizer) and outputs (soybean grains and animal tissue) and the K remaining in plant and soil, respectively, were calculated. Potassium cycling increased with increasing grazing intensity and the balance, despite negative, with a higher deficit in areas with higher grazing intensity, did not influence soybean yield.