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Abstract: Information systems used in farming systems are characterized by high complexity. They should be composed of inter-related economic and biological components capable of working in a dynamic and continuous manner, receiving data and producing results within an organized production process. Taking this complexity into account, in this study we propose a novel conceptual macromodel with a system approach of the agricultural and livestock production environment to be adopted as information system in order to support the decision making process. This model is capable of representing the innumerable aspects of a farm production system aiming to help farm producers understand and manage their production system. To better understand the general model and its nuances, several submodels (input models) were built based on adaptation of pre-existing research, among which we mention: meteorological, pasture, animal, crop–livestock integration, crop, soil, pasture-animal, and pasture-soil submodels. The combination of these submodels originates and configures the farm production system structure. Among the main outputs of the proposed model are the economic results, based on agricultural and livestock productivity, the environmental impact assessment, and the analysis of operational risk. A qualitative approach was used with an exploratory descriptive design to carry out this research, based on literature review, interviews, and meetings with experts to refine and validate the proposed model. The refinement of the conceptual model was based on the Delphi method, which allowed the collection of data and peculiarities of the object under study, guided its development to achieve the goals of this research, and allowed the register of several issues for further studies. The validation of the model, also using a qualitative approach, was performed employing conceptual, face, and subsystem validation procedures, also applying the Delphi method. This way, we aimed to identify the weak and strong points of our conceptual model, its main shortcomings and limitations, and the variables that should be optimized, in theoretical and practical perspectives, so that this model can be improved. [Copyright &y& Elsevier]

Questions: (i) How does a strategic deferment influence both shoot and root biomass in South American Campos natural grassland after a long time of contrasting livestock grazing intensities? (ii) How do functional strategies of plants to tolerate or avoid grazing affect patterns of aboveground and belowground biomass? Location: A natural Campos grassland in the Central Depression of Rio Grande do Sul State, Southern Brazil (latitude 30°05′27″ S, longitude 51°40′18″ W, and altitude 46 m). Methods: We studied the effects of deferments (spring or autumn) at moderate and severe livestock grazing intensities (maintained by adjusting contrasting forage allowances during 25 years) on the cover of dominant species, and aboveground and belowground biomass. The experiment was arranged in a completely randomized design with three replications of grazing exclusions, applied simultaneously at moderate and severe grazing intensities. Measurements of above‐ and belowground biomass and the coverage of the five dominant species were performed before and after grazing exclusion periods. Results: Under severe grazing intensity, erect‐growing grasses were replaced by prostrate species, which were able at least to maintain the belowground biomass found at moderate grazing intensity. In response to deferments, severe grazing intensity changed toward a significant increase in aboveground biomass and in the coverage of plants with erect growing habit. However, total belowground biomass remained unaffected by exclusions in both grazing intensities. The relation of root:shoot biomass was lower under moderate grazing intensity, and showed a negative response to deferment treatments at severe grazing intensity. Conclusion: Long‐term contrasting grazing intensities applied in South American Campos grasslands determine several changes in above‐ and belowground relationships. Prevalence of prostrate plants under severe grazing is associated with a high partitioning capacity of assimilates toward the subterranean biomass, higher than in the tall species predominant under moderate grazing. The fast recovery of aboveground biomass, the maintenance of the underground biomass and the increase of tall grasses in response to deferments reveals the high resilience capacity of this ecosystem after a long‐term period of overgrazing. [ABSTRACT FROM AUTHOR]

Grazing intensity manipulation can affect structure and botanical composition of the pasture. The objective of this research was to evaluate the effects of different forage allowances and different seasonal sequences of forage allowance (FA) on the species population dynamics in the rangelands of Campos Sulinos. The botanical composition evaluations were made in January 12th and July 17th, using BOTANAL method. Treatments were of different FA (kg DM 100kg-1 of live weight day-1): 8, 12, 16 all around the year; and different sequences of FA: 8 on spring and 12 at the rest of year (8-12); 12 on spring and 8 at the rest of year (12-8) and 16 on spring and 12 at the rest of year (16-12). The statistical design used was randomized blocks with two replications. The forage allowance led to changes in botanical and structural composition of vegetation. It can be inferred that the forage allowance variation on the vegetation had higher impact on smaller forage allowances . [ABSTRACT FROM AUTHOR]

Grass species grown in South American natural grasslands present different growth strategies related to variations in specific leaf area (SLA), leaf dry matter content (LDMC) and possible nitrogen (N) allocation. Nitrogen fertilisation can have effects on physiological processes such as CO2 assimilation; however, these responses can change depending on the growth strategy adopted by each species. The aim of the present study is to determine the effects of N fertilisation on SLA, LDMC and CO2 assimilation in eight C4 grass species: Axonopus affinis , Paspalum pumilum , P. notatum , P. urvillei , P. plicatulum , Andropogon lateralis , Saccharum angustifolium and Aristida laevis. These species were cultivated in pots filled with soil subjected to two conditions of N availability: nil (control) and 200 mg N kg–1 soil. The SLA of Axonopus affinis was 5.4 times higher than that of Aristida laevis. Axonopus affinis and P. pumilum recorded the lowest LDMC, their leaves showed 53% lower LDMC than observed for Aristida laevis , on average. Resource-capture species showed variation in leaf area with N addition to values 20% higher than the control, whereas species characterised by a resource-conservation growth strategy recorded variation in leaf area with N addition to values only 8% higher than the control. With N addition, the CO2 assimilation of resource-capture species represented variation (increase) nine times that of resource-conservation species compared with their respective controls. Resource-capture species have greater CO2 capture potential than resource-conservation species, mainly a result of N addition. The capacity for CO2 assimilation and response to nitrogen fertilisation by grasses from South American natural grasslands depends on the species present. Grasslands with species of high specific leaf area (SLA) and low leaf dry matter content (LDMC) have higher response potential to nitrogen fertilisation, with increase of 20% in leaf area and also have a potential 13 times higher for CO2 sequestration than grasslands with species with low SLA and high LDMC. [ABSTRACT FROM AUTHOR]

The rational use of N fertilization is essential to increase the recovery efficiency and crop productivity and decrease the cost of production. The objective of this study was to assess forage yield (TDM), tillers population density (TPD) and N use efficiency (NUE) in six Paspalum notatum Flüggé genotypes in response to N fertilization. The experimental design involved randomized blocks on a subdivided plot design. In 2014-2015 the TDM was higher for the C22 and B26 hybrids (P < 0.0001), which were similar to each other, with an average of 6173 kg DM ha-1 yr-1. In 2015-2016 the TDM of the genotypes ranging from 7053 to 13773 kg DM ha-1 yr-1, for pastures fertilized with 0 and 480 kg N ha-1 yr-1, respectively. An interaction was found between Genotype x N fertilization level (P = 0.0155) for TDM in 2016-2017. In the years 2015-2016 and 2016-2017 the C22 hybrid standed out as the genotype with the highest tiller production in response to N fertilization. In the year 2014-2015 NUE was higher (P = 0.0015) in the N fertilization levels N60, being of 15.5 kg DM kg-1 N. In the years 2015-2016 and 2016-2017 the NUE was higher at fertilization level N120 (P < 0.05), being of 21.1 and 31.5 kg DM kg-1 N, respectively. The C22 hybrid was distinct as the genotype with the highest DM yield and superior tillering characteristics. The N fertilization level of 120 kg N ha-1 yr-1 promoted greater NUE in all P. notatum genotypes. [ABSTRACT FROM AUTHOR]

Native pastures are very important food sources for bovine and sheep production in the Pampa biome. Ryegrass introduction and nitrogen fertilization are alternatives aimed at a more sustainable intensification of livestock production. The objective of this study was to evaluate the effects of doses of nitrogen fertilizer in native pasture with ryegrass introduction on soil chemical acidity indicators. The experiment consists of a secondary native pasture under continuous grazing. The area was limed, and three different nitrogen rates (0, 100, and 200 kg ha-1 year-1 of nitrogen) were applied. Basis and aluminum saturation and pH were evaluated in 0-10 and 10-20 cm soil layer. In 0-10 cm soil layer, pH decreases 0.27 units per 100 kg ha-1 year-1 of nitrogen applied. In 10-20 cm soil layer, pH decreases of 5.3 to 4.7 and 4.6 with dose of nitrogen of 100 and 200 kg ha-1 year-1, respectively. Long-term nitrogen fertilization in native pasture with ryegrass introduction resulted in soil acidification until 20 cm soil depth. [ABSTRACT FROM AUTHOR]

Moderate grazing intensity is considered the basic requirement to enhance ecosystem function in grasslands. Yet, deterioration by overgrazing is common in many biomes, including Campos grasslands in South America. Understanding how grazing management can lead to recovery of ecosystem function is essential to design and implement effective strategies for sustainable use of this resource. In a long‐term field experiment carried out in Southern Brazil, we studied the effects of temporal grazing exclusions (spring or fall) at moderate and severe livestock grazing intensities (maintained by adjusting contrasting forage allowances) on the species richness, botanical composition, forage mass, sward height, and photosynthetic active radiation intercepted. The experiment was arranged in a completely randomized design with three replications of grazing exclusions, applied simultaneously at moderate and severe grazing intensities. Moderate grazing intensity showed a bimodal structure of shorter and taller canopies, and high species richness. Severe grazing created a shorter and homogeneous sward structure characterized by less standing biomass and species loss. In response to grazing exclusions, sward height, standing biomass, and light interception recovered almost to the levels of moderate grazing. Further, within 2 years grass species richness increased and botanical composition changed toward grasses with erect habit prevailing in moderate grazing intensity. Our study confirms that (1) moderate grazing intensities allow the coexistence of high number of species and (2) spring grazing exclusions of long‐term overgrazed grasslands can lead to a quick start to recover the grass species richness, primary productivity, and species composition like that prevailing in well‐managed grasslands. [ABSTRACT FROM AUTHOR]

Profitability and environmental benefits of beef cattle raised on natural pasture or combined with soybean in tropical biomes need to be better evaluated. The objective of this research was to simulate and evaluate three common pastured beef grazing systems in southern Brazil, estimating profitability and the environmental impacts of carbon footprint (CF) measured as kg of CO 2 equivalent per kg of body weight produced (BWP), water footprint (kg of water used/kg of BWP) and energy footprint (MJ of energy used/kg of BWP) using the Integrated Farm System Model version 4.2. Simulations were run for Angus beef cattle raised on natural pasture (NP), natural pasture with low levels of grain supplementation (NPS), and NPS combined with soybean production (NPSC). Net animal weight produced (kg/ha/year) increased 7.9% for NPS and NPSC when compared with the NP system. Natural pasture production costs per hectare were lower (US$ 114) than that of NPS (US$ 126) and NPSC (US$ 233), while NP had a net return per hectare only 2% greater than NPS. Even though the gross income from animal sales was 5% higher in NPS than NP, the elevated cost of purchased feeds reduced net return per hectare. While costs were higher for NPSC, diversifying with soybean production, a high value commodity for cash sale, was profitable resulting in 44% and 47% greater net return per hectare than NP and NPS, respectively. Natural pasture with low supplementation (NPS) decreased CF by 2% when compared with NP due to faster weight gain from supplementation despite higher emissions from feed production. Furthermore, CF was also 6% lower for natural pasture combined with soybeans (NPSC) compared with NPS. However, the energy and water footprints and erosion increased with the greater use of both purchased feed and inputs required for feed and cash crop production. It can be challenging to increase beef cattle productivity and diversification to lower GHG emissions while minimizing water and energy use and soil erosion. [ABSTRACT FROM AUTHOR]

Invasion by exotic grasses is a severe threat to the integrity of grassland ecosystems all over the world. Because grasslands are typically grazed by livestock and wildlife, the invasion is a community process modulated by herbivory. We hypothesized that the invasion of native South American grasslands by Eragrostis plana Nees, an exotic tussock-forming grass from Africa, could be deterred by grazing if grazers switched dietary preferences and included the invasive grass as a large proportion of their diets. Bos taurus (heifers) and Ovis aries (ewes) grazed plots with varying degrees of invasion by E. plana in a replicated manipulative experiment. Animal positions and species grazed were observed every minute in 45-min grazing session. Proportion of bites and steps in and out of E. plana tussocks were measured and used to calculate several indices of selectivity. Both heifers and ewes exhibited increasing probability of grazing E. plana as the proportion of area covered by tussocks increased, but they behaved differently. In agreement with expectations based on the allometry of dietary preferences and morphology, ewes consumed a low proportion of E. plana, except in areas that had more than 90% E. plana cover. Heifers consumed proportionally more E. plana than ewes. Contrary to our hypothesis, herbivores did not exhibit dietary switching towards the invasive grass. Moreover, they exhibited avoidance of the invasive grass and preference for short-statured native species, both of which should tend to enhance invasion. Unless invasive plants are highly palatable to livestock, the effect of grazing to deter the invasion is limited, due to the inherent avoidance of the invasive grass by the main grazers in the ecosystem, particularly sheep. [ABSTRACT FROM AUTHOR]