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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...

Objectives To evaluate the disk diffusion technique after 4 and 6 h directly from positive blood culture bottles of Enterobacteriaceae using the rapid antimicrobial susceptibility test (RAST) breakpoints established by The European Committee on Antimicrobial Susceptibility Testing (EUCAST). Methods A total of 61 isolates of Escherichia coli and Klebsiella spp. were selected. The results were assessed using the RAST breakpoints (4–6 h) as well as the standard breakpoints (18 h) from EUCAST. Results The vast majority of the zone diameters of E. coli and Klebsiella spp. were optimally readable after 6 h of incubation. RAST at 6 h presented best results of categorical agreement (CA) and errors (CA = 94.4%, minor errors [mE] = 4.3%, major errors [ME] = 0.8% and very major errors [VME] = 0.4%) compared to RAST at 4 h (CA = 84.3%, mE = 13.0%, ME = 3.2% and VME = 0.4%). The proportion of results in the area of technical uncertainty decreased over time: from 13.8% at 4 h to 6.8% at 6 h. According to the U.S. Food and Drug Administration and ISO criteria, early readings at 6 h using the RAST breakpoints provided acceptable results (CA > 90%), whereas accuracy of results at 4 h was unacceptable (CA Conclusion These data indicate that the early readings at 6 h using the RAST breakpoints for all antibiotics tested in this study (except amikacin) may be used in the clinical microbiology laboratory to anticipate the antimicrobial susceptibility test results of blood cultures. Early readings at 4 h (RAST breakpoints) may also be used, but not for all antibiotics.

Tillage activities play a crucial role in impacting soil physical and chemical properties, which in turn alter soil biochemical activities and microbial community structure. In this study, responses of soil biochemical activities and microbial community structure to short‐term (NTS, 10 years) no‐till (NT) systems were studied in comparison with conventional till (CT) at four different locations (Garretson, Crooks, Beresford and Mitchell) in South Dakota, USA. Data showed that the NTL resulted in increased soil labile and microbial biomass carbon (C) and nitrogen (N) compared with the CT treatment at the Garretson, Crooks and Beresford sites. At the Crooks and Beresford sites, soils under NTL and NTS had significantly increased the β‐glucosidase, urease, arylamidase, acid and alkaline phosphatase and arylsulphatase enzyme activities compared with those under CT treatment. The β‐glucosidase, urease, acid phosphatase and arylsulphatase enzyme activities showed significant correlations with the microbial biomass content of the soils. Phospholipid fatty acid (PLFA) analysis showed increased PLFA content in NTL soils compared with the CT. The content of total bacterial, actinobacterial, Gram‐positive bacterial, total fungal, arbuscular mycorrhizal fungal (AMF) and saprophyte PLFAs was consistently increased in the NTL and NTS compared with the CT soils at the Garretson site. These differences were more pronounced between NTL and CT systems than between NTS and CT systems in most of the studied sites. The findings suggest that usage of NT for a longer duration is highly beneficial to soil labile C and N pool retention and enzyme activities, and provides less disturbance to soil microbial activities and their functions, which in turn regulates nutrient transformation. Our results also suggest that converting CT soils into NT can improve some soil health indicators even over a short duration, and hence adopting NT can enhance soil microbial and plant growth. HIGHLIGHTS: NTS and NTL systems increased soil labile C and N and microbial biomass as compared to CT Total fungi biomass was significantly enhanced under NT compared with CT Short‐term NT significantly increased β‐glucosidase activity at Crooks and Beresford sites compared to CT Compared to the CT system, NT significantly increased soil biological health

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...

The objective of this study was to evaluate the short-term dynamics of chemical species of sulfate and the main basic cations in the soil solution affected by the application of different s...

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.

Faccio Carvalho, Paulo César de. Federal University of Rio Grande do Sul. Integrated Crop-Livestock Systems Research Group. Porto Alegre, Brazil. Savian, Jean Víctor. Instituto Nacional de Investigación Agropecuaria (INIA). Estación Experimental INIA Treinta y Tres. Treinta y Tres, Uruguay. Della Chiesa, Tomás. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Della Chiesa, Tomás. CONICET – Universidad de Buenos Aires. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Souza, William de. Federal University of Rio Grande do Sul. Integrated Crop-Livestock Systems Research Group. Porto Alegre, Brazil. Terra, José Alfredo. Instituto Nacional de Investigación Agropecuaria (INIA). Estación Experimental INIA Treinta y Tres. Treinta y Tres, Uruguay. Pinto, Priscila. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Pinto, Priscila. CONICET – Universidad de Buenos Aires. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Posselt Martins, Amanda. Federal University of Rio Grande do Sul. Integrated Crop-Livestock Systems Research Group. Porto Alegre, Brazil. Villarino, Sebastián Horacio. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias. Unidad Integrada Balcarce. Balcarce, Buenos Aires, Argentina. Villarino, Sebastián Horacio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce (EEA Balcarce), Buenos Aires, Argentina. Trindade, Júlio Kuhn da. Department of Agricultural Research and Diagnosis. Secretariat of Agriculture. Livestock and Rural Development of Rio Grande do Sul. Brazil. Albuquerque Nunes, Pedro Arthur de. Federal University of Rio Grande do Sul. Integrated Crop-Livestock Systems Research Group. Porto Alegre, Brazil. Piñeiro, Gervasio. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Piñeiro, Gervasio. CONICET – Universidad de Buenos Aires. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Piñeiro, Gervasio. Universidad de la República. Facultad de Agronomía. Uruguay. The Rio de la Plata region comprises central Argentina, Uruguay, and southern Brazil. Modern agriculture developed around 1900 with recent decades being characterized by the advance of cropping areas over native grasslands. Highly specialized agriculture has decoupled crop and livestock production but has succeeded in intensifying yields. However, significant losses of ecosystemservices have been reported. Thus, questions have been raised on the sustainability of this pathway. A glance at world regions that have experienced similar trends suggests that an urgent course correction is needed. A major concern has been the lack of diversity in regions with highly specialized agriculture, promoting renewed interest in integrated crop-livestock systems (ICLS), not only because ICLS are more diverse than specialized systems, but also because they are rare examples of reconciliation between agroecosystem intensification and environmental quality. Consequently, this paper discusses alternatives to redesign multifunctional landscapes based on ICLS. Recent data provide evidence that recoupling crop and animal production increases the resilience of nutrient cycling functions and economic indicators to external stressors, enabling these systems to face climate-market uncertainty and reconcile food production with the provision of diverse ecosystem services.\nFinally, these concepts are exemplified in case studies where this perspective has been successfully applied. il., grafs.

In the last decades, population growth worldwide boosts agricultural demand for food production. This huge driver rendered global food production more and more specialized, so agricultural landscapes became uniform and monotonic. The loss of diversity is a strong evidence of how modern agricultural landscapes have been disconnecting from nature. Evidence of environmental side-effects from this pathway are abundant in literature. Now, society is pressing towards changing practices aiming for healthy diets and sustainable food production systems. This raises the question: how to reconnect nature and agriculture in the context of future food production? In this review we propose a reconnection process based on the principles of ecological intensification or sustainable intensification. The integrated crop-livestock systems (ICLS) are the most consolidated technological pathway for reconciling crop production with natural processes. These systems are diverse and can partially mimic natural ecosystems exploring the synergies of natural biological processes, while achieving high levels of food production. ICLS promote soil improvements and mitigate greenhouse gas (GHG) emissions, reducing the agricultural share of global warming and climate change. Besides, these systems are more efficient in the use of nutrients and can optimize the use of other inputs such as pesticides. We present evidence of soil health and biogeochemical cycle restoration in addition to system stability improvement, and assume those symptoms as evidence of mixing crops and livestock fostering reconnection with natural processes.

International audience; AbstractIntegrated crop-livestock systems (ICLS) can be an alternative to increase the productivity of agroecosystems by enhancing nutrient cycling via grazing animals. Despite the holistic approach that bears the designing of ICLS, fertilization practices are proceeded in a conventional crop basis, disregarding nutrient fluxes at the appropriate spatial and temporal dynamics. We argue that fertilization practices in ICLS must follow the same integrated approach. To test this, we compared a conventional crop fertilization strategy versus a system fertilization approach applied to two production systems being a conventional cropping system and ICLS. The conventional cropping system consisted of a soybean crop succeeded by a non-grazed Italian ryegrass cover crop. The ICLS model consisted of a soybean-Italian ryegrass rotation grazed by sheep. In the conventional crop fertilization strategy phosphorus and potassium were applied at soybean sowing and nitrogen at the Italian ryegrass establishment. The system fertilization consisted of the application of all nutrients during the Italian ryegrass establishment. Accordingly, treatments were fertilization strategies in a factorial framework with production systems randomly distributed in a complete block design with four replicates. Results indicated for the first time greater daily herbage accumulation rate (24%; P < 0.01) and total herbage production (18%; P < 0.05) in the system fertilization compared with conventional crop fertilization. Consequently, system fertilization allowed for greater stocking rates in the pasture phase (17%; P < 0.05). The ICLS presented greater equivalent soybean yield (P < 0.001), energy production (P < 0.01), and system productivity (P < 0.05) compared with the cropping system, regardless of fertilization strategies. Soybean yield was not affected by fertilization strategies or grazing. In conclusion, the adoption of system fertilization strategy and crop-livestock integration enhance the production without jeopardizing soybean grain yields, so that land use is optimized by a greater energy production per unit of nutrient applied.

The use of hybrid genotypes is a good alternative for increasing the flooded rice yield. However, there is a need for validation of the fertilizer management under different edaphoclimatic conditions and its greater profitability. This study aimed to evaluate the grain yield and profitability of rice hybrids in relation to N doses and fertilization with P and K. Five hybrid cultivars and the conventional IRGA 424 CL cultivar combined with four N doses (0, 100, 150 and 200 kg ha-1) were evaluated, all with fixed doses of 90 kg ha-1 of P2O5 and 150 kg ha-1 of K2O, besides an additional treatment without the addition of fertilizers. The N application increases, on average, by 10 and 35 % the flooded rice yield in years with favorable and unfavorable climatic conditions, respectively. Regardless of the year and genotype, the highest yields are obtained with doses of N between 106 and 200 kg ha-1, with the most profitable dose being the 150 kg ha-1 one (22 % higher than for the absence of N). The hybrids produce an average of 20 % more grains than the IRGA 424 CL cultivar, increasing the profitability by 18 %. In soil with adequate P and K availability, there is no increase in yield due to the application of these nutrients. However, in deficient soil, the fertilization with P and K increases the grain yield by 21 %. RESUMO O uso de genótipos híbridos é uma boa alternativa para aumentar a produtividade do arroz irrigado. Há, no entanto, a necessidade de validação do manejo da adubação em diferentes condições edafoclimáticas e de sua maior rentabilidade. Objetivou-se avaliar a produtividade de grãos e a rentabilidade de híbridos de arroz relacionadas a doses de N e à adubação com P e K. Avaliaram-se cinco cultivares híbridas e a cultivar convencional IRGA 424 CL combinadas com quatro doses de N (0; 100; 150; e 200 kg ha-1), todas com doses fixas de 90 kg ha-1 de P2O5 e 150 kg ha-1 de K2O, além de um tratamento adicional, sem o uso de fertilizantes. A aplicação de N incrementa, em média, em 10 e 35 % a produtividade do arroz irrigado em anos com condições climáticas favoráveis e desfavoráveis, respectivamente. Independentemente do ano e genótipo, as maiores produtividades são obtidas com doses de N entre 106 e 200 kg ha-1, sendo a dose de maior rentabilidade a de 150 kg ha-1 (22 % superior à ausência de aplicação de N). Os híbridos produzem 20 % a mais de grãos, em média, que a cultivar IRGA 424 CL, incrementando a rentabilidade em 18 %. Em solo com disponibilidade de P e K adequada, não há incrementos em produtividade pela aplicação desses nutrientes. Porém, em solo deficiente, a fertilização com P e K incrementa em 21 % a produtividade de grãos.

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.

O objetivo desta pesquisa foi avaliar como o manejo da adubação nitrogenada em cobertura no milho e os volumes de irrigação afetam a dinâmica do nitrogênio no perfil do solo e o rendimento de grãos de milho. Para isso, foi avaliada uma área experimental que vem sendo cultivada em sistema plantio direto há 22 anos. Os tratamentos constaram da combinação de manejos de nitrogênio em cobertura (testemunha sem nitrogênio em cobertura, dose única de 300 kg ha-1 e essa dose parcelada em duas vezes) e volumes de irrigação (20 e 100 mm). As amostragens de solo foram realizadas dez dias após a primeira adubação de N em cobertura e dez dias após a segunda adubação de nitrogênio em cobertura. Independentemente do volume, a irrigação promoveu o aumento nos teores de nitrato nas camadas subsuperficiais (20-30 e 30-40 cm) após a aplicação das doses de nitrogênio em cobertura. O parcelamento da adubação nitrogenada foi uma alternativa eficiente para diminuir os teores de nitrato nas camadas subsuperficiais do solo, para ambos os volumes de irrigação. Entretanto, isso não se refletiu em ganho de produtividade e em retorno econômico quando comparado à aplicação única de nitrogênio em cobertura, independentemente do volume de irrigação.

Long-term integrated crop-livestock system enables constant and more efficient nutrient cycling because animal, pasture and crop residues release nutrients at different rates. Therefore, appropriate management of these systems is needed to maximize benefits from nutrient cycling. The objective of this study was to evaluate how grazing intensity affected the release rates of phosphorus (P) and potassium (K) in pasture, dung and soybean residues in a no-till long-term integrated crop-livestock system. The experiment was established in 2001 on a clayey Oxisol after soybean harvest. Treatments consisted of pasture with sward heights maintained at 1020, 30 and 40 cm by different cattle stocking rates and a non-grazed (NG) treatment. Decomposition and release rates of nutrients in the pasture and dung were determined using litter bags, which were installed at soybean seeding and pasture seeding during two pasture-crop cycles (2009–2011). Lighter grazing intensities resulted in greater P release rate from pasture and dung residues. Pasture and dung residues released K at a very high rate and were not influenced by grazing intensity. The P and K released from soybean residue were not affected by grazing intensity; however, decomposition of soybean leaves was greater than of stems. Greatest rates of total P and K released were from pasture and dung residues under lighter grazing intensities and in the NG areas. Large amounts of P (~25 kg ha−1) and K (~130–180 kg ha−1) were cycled in a complete soybean-beef cattle integrated system and must be considered in the fertilization management.

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.

Soil acidity can impair biological N2 fixation (BNF) and increase soybean (Glycine max L.) reliance on soil N to satisfy its plant N demand. This study aimed to evaluate the effect of liming, fertilization strategy, and grazing on: i) the N supplied via BNF process, ii) partial N-balance, and iii) soybean yield, in an integrated crop-livestock system under a non-tilled sandy and acidic Acrisol. Initial soil conditions were soil pH of 4.0 and Al saturation of 50%. Limestone was applied to rise soil pH to 6.0 and a control area was kept with the initial soil conditions. Soybean was grown in the summer and Italian ryegrass (as a cover crop or grazed by sheep) in the winter. Fertilization strategies consisted in applying P and K prior to soybean or ryegrass. Partial N-balance was calculated by the difference between N derived from BNF and N removed in soybean seeds. Contribution of N from the atmosphere to soybeans was on average 62 and 66% in plots without and with liming, respectively. The fixed-N was 27% greater under low soil acidity due to lime. Partial N-balance was positive in both treatments, but 57% greater in the limed- relative to the non-limed (+58 kg ha−1) soils, resulting in 11% soybean yield increase when lime was added. The most relevant soil chemical properties influencing N fixation were soil pH and Al saturation. Grazing and fertilization strategies had no effect on soil acidity properties, N supply, and soybean evaluations. Further research should explore the long-term effect of grazing, fertilization strategies, and liming.