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The hydrological variable evapotranspiration (ET) is challenging to estimate because it cannot be measured directly in natural environments (except in small plots). The uncertainties associated with the models used for its prediction have increased under climate change conditions. We studied the influence of stomatal resistance on ET estimates using the Penman-Monteith method as projected by three general circulation models in two emission scenarios (RCP4.5 and RCP8.5) for future climates throughout the twenty-first century (2010–2039, 2040–2069, and 2070–2099). We also investigated the probable ET rate changes in relation to the current (30 years average, 1980–2009) climate conditions for the Paraná state in the southern region of Brazil. The results were regionalized to help policymakers assess climate change impacts and design adaptation measures. ET increases of up to 15% were found in future climate conditions, which may lead to a significant increase in the water demand for agricultural crops. However, we believe that plant morphophysiological changes may occur under atmospheric CO2 enrichment conditions and that a possible reduction in stomatal conductance will result in lower ET increases than those obtained with the traditional Penman-Monteith method. When considering future climate scenarios, we propose the equation be adjusted to consider stomatal resistance as a function of CO2 concentrations.

The intricate relationship between climate and society in a given region demands a profound understanding of climate patterns, especially in agricultural areas like Diamantina, Minas Gerais (MG), recognized by the Food and Agriculture Organization (FAO) as the birthplace of the first Globally Important Agricultural Heritage System (GIAHS) in Brazil, situated in the southwest region of the country. Given the growing concerns about climate change, we conducted a meticulous analysis of the climatic characteristics of Diamantina-MG. To achieve this, we examined historical meteorological data from 1973 to 2022, employing the Mann–Kendall and Sen’s slope tests to analyze trends. Additionally, we utilized three global climate models (GCMs) under different shared socioeconomic pathways (SSPs) to predict future climate scenarios (2021–2100) based on the projections of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). Furthermore, we used Köppen and Thornthwaite climate classification methodologies to characterize both the current and future climate conditions of the region. Our results indicate that, historically, Diamantina-MG has experienced significant increases in minimum temperature, indicating a warmer climate in recent decades. For temperature, the projections show a consensus among models, projecting a continuous increase, potentially reaching up to 5.8 °C above the historical average temperature (19.2 °C) by the end of the century. Regarding rainfall projections, they show greater uncertainty, with discrepancies among models observed until 2060. However, specifically for the second half of the century (2060–2100), the models agree that there will be increases in annual rainfall. Regarding the climatic types of the region, we found that the current Köppen Cwb and Thornthwaite B3rB’3a’ classifications could shift to Aw and B1wA’a’, representing a humid tropical savanna climate with longer periods of water deficiency, considering the impacts resulting from increased air temperature and evapotranspiration. In summary, the study’s results indicate that climate changes are occurring and are likely to intensify in the Jequitinhonha Valley region, MG, in the future. The analysis of these data, from the perspective of the Brazilian GIAHS sustainability, reveals the importance of considering adaptation and mitigation measures to ensure the resilience of agricultural systems and local communities in the region that face these significant environmental changes.

Brazil is one of the world’s largest producers of beef cattle and dairy products, which requires high forage yield to attend grass-fed animals’ demand. Among the grass species adopted in the forage production system in Brazil, the Brachiaria genus stands out. This genus comprises nearly 85% of all planted forage area. In general, forage production systems in Brazil are essentially rainfed, and thus susceptible to seasonal soil water stresses. Selecting the suitable Brachiaria cultivar for lands susceptible to periodic waterlogging and dry spells is crucial to enhance forage yield, and consequently, to reduce the environmental footprint of the livestock sector. In this research, we investigated the performance of three recent commercial Brachiaria brizantha cultivars (Piatã, BRS Paiaguás, and MG13 Braúna) extensively adopted in Brazil’s grazing systems subjected to different ranges of soil water potential. For three cutting periods, yield related-variables (e.g., plant height, leaf area, dry biomass, and water use efficiency) were measured. Our results point to the existence of a low drought-resistant trait among cultivars, indicating the need for releasing better-adapted cultivars to cope with reduced soil water availability. All cultivars achieved higher performance at soil water pressure head between −15 kPa and −25 kPa; and in general, the cultivar. Piatã showed slightly superior results to most of the treatments.

ABSTRACT Spain contains a third the entire irrigated area of Europe, accounting for 15% of the cultivated area of the country and almost 60% of the national agricultural production. Knowledge of the spatial and temporal variability of reference evapotranspiration (ETo) and the probabilistic theory of extreme events is crucial for the elaboration of sustainable irrigation projects. The objective of this work was to define the frequency distribution that best describes ETo for the design of irrigation systems in the region of Andalusia. We used ETo data for the period 2001 to 2015 from 56 meteorological stations. The values were accumulated over three consecutive days. For all accumulated periods, nine probability distributions were adjusted. The probability distribution that best described ETo for the design of irrigation systems in the region was the Gumbel II distribution. The maximum daily ETo to be considered in irrigation projects in this region is, on average, 10 mm. The accumulated ETo for periods of 5, 10, and 30 days that should be considered are, on average, 42 mm, 78, mm and 224 mm, respectively. RESUMO A Espanha possui um terço de toda área irrigada da Europa. A área irrigada no país responde por 15% da área cultivada e quase 60% da produção agrícola nacional. O conhecimento da variabilidade espacial e temporal da evapotranspiração de referência (ETo) e da teoria probabilística dos eventos extremos é um ponto essencial para elaboração de projetos sustentáveis de irrigação. O objetivo do trabalho foi analisar a distribuição de frequência que melhor descreve a ETo visando o dimensionamento de sistemas de irrigação da região de Andaluzia, Espanha. Foram utilizados dados de ETo de 56 estações meteorológicas com extensão das séries entre os anos de 2001 a 2015. Estes valores de ETo foram acumulados em três períodos consecutivos de dias. Para todos os períodos acumulados ajustaram-se nove distribuições de probabilidade. A distribuição de probabilidade que melhor descreveu a ETo visando o dimensionamento de sistemas de irrigação da região foi a Gumbel II. A ETo diária máxima a ser considerada em projetos de irrigação na mesma região é de 10 mm, em média. Já as ETo acumuladas em períodos de 5, 10 e 30 dias que devem ser consideradas são, em média, de 42 mm, 78 mm e 224 mm, respectivamente.

This work had as objectives to use the Sunn Hemp (Crotalaria juncea L.) to evaluate the residual effect in the soil of levels of water salinity and nitrogen doses, and the occurrence of spatial dependence within the experimental area. In previous years, the experimental area received six consecutive trials, which tested different levels of nitrogen and water salinity on different crops. The same experimental design was applied to this trial, that is, a randomized block design with split-plots (5 x 3), corresponding to the residual effect of water salinity and nitrogen, and four replications. The variables determined were: the plant height on six dates after the sowing, and the dry mass of the shoot, root and the whole plant. The data were firstly subjected to the variance analysis of the residual effects and to the study of spatial variability through geostatistics. The variance analysis did not show significant residual effects of the levels of salinity and nitrogen doses in the soil on the height and dry mass of Sunn Hemp. It was observed a spatial dependence, from moderate to high, in all dates, for height and dry mass of Sunn Hemp.

The experiment was conducted in 2014, in a completely randomized factorial design (5x6), with three replications. The factors were soil classes (Typic Ustipsamments, Typic Haplustults, Typic Haplustepts, Typic Ustifluvents, and Typic Haplusterts) and levels of irrigation water salinity (0.5, 1.0, 2.0, 3.0, 4.0, and 5.0 dS m-1). Increasing salinity of irrigation water caused increase in leaf contents of macronutrients in all soils. Adequate leaf contents of N, K, and Mg were observed in plants grown in all soils except K in Typic Haplusterts and Mg in Typic Ustipsamments. Appropriate P levels were observed only in Typic Haplustepts, and Ca only in Typic Haplustults and Typic Ustifluvents. Increased salinity of irrigation water caused increased leaf contents of micronutrients in all soils except copper in Typic Ustifluvents, iron in Typic Haplusterts and Typic Haplustults, and manganese in Typic Ustipsamments and Typic Haplustults.

O uso das ferramentas da geotecnologia conciliadas a delimitações de bacias fomenta estudos das características fisiográficas da bacia hidrográfica, fundamental no planejamento e tomadas de decisões para conservação, uso e ocupação do solo. O estudo objetivou a delimitação da bacia hidrográfica Canela Fina para verificar se a mesma tem propensão a enchente. Com uso do software QGIS 3.18.1. Zürich as metodologias por meio do Modelo Digital de Elevação (MDE) obtido da Shutter Radar Terrain Mission (SRTM) com resolução de 30 m. A bacia apresentou área de 116,50 km2 e perímetro de 95,90 km. O fator de forma foi 0,31, índice de circularidade 0,15, coeficiente de compacidade 2,49, coeficiente de I-Pai-Wu 1,59 e densidade hidrográfica de 0,97 canais/km2. A altitude máxima da bacia foi 244 m, mínima 180,66, com uma declividade máxima de 47,68% e média de 7,08%, com razão de relevo de 3,22 m/km. A bacia foi classificada como 4º ordem, padrão de drenagem dendrítica, índice de sinuosidade foi de 1,23 e com densidade de drenagem de 1,41 km/km2. O uso e ocupação do solo entre os anos de 1985 à 2020, pastagem aumentou 35,60% a sua área e área urbanizada 12,64%, a formação florestal e campestres tiveram redução de 36,90% e 39,61%, respectivamente. Conclui-se que a bacia não possui susceptibilidade a enchentes.

Long-term changes in important weather variables such as evapotranspiration (ET) and precipitation are expected as a response to climate change. These changes may require adjustments to current strategies of planning and management of water resources. The objective of this work was to conduct a spatiotemporal characterization of evapotranspiration in the State of Paraná, Brazil, including in this approach a temporal trend analysis. A similar analysis was also conducted for precipitation. Thus, the historical data (1980-2010) from 33 weather stations were analyzed. The spatial distribution of the data was carried out by geostatistical techniques (ordinary kriging) and the trend analysis by the tests Mann-Kendall and Sen. According to the results, evapotranspiration increases from the coast to the interior of the state, with the highest values in the northeast and northwest regions, reaching levels of about 1200 mm yr-1. The temporal variability of the ET presented a significant upward trend in 12% of the locations, with increases from 2.5 to 7.0 mm yr-1. Precipitation was higher in the coastal and south-central regions and the lowest amounts were identified in the northeast and northwest regions. The precipitation trend analysis indicated a significant downward trend in precipitation volume of five locations. The evapotranspiration and precipitation showed, in general, no statistically significant trends in most of the stations analyzed; however, the upward trends for ET and downward trends for precipitation indicate local changes in the State of Paraná.

O objetivo do presente estudo foi avaliar o efeito da densidade populacional sobre components de produção de milho doce durante dois anos agrícolas. O delineamento experimental utilizado foi o de blocos completos casualizados com quatro repetições. Os tratamentos constitu ram-se da combinação entre híbridos de milho doce (Tropical Plus e RB-6324) e populações de plantas (40.000, 55.000, 70.000, 85.000 e 100.000 plantas ha^(-1)), no esquema fatorial 2 x 5, avaliados em dois anos agrícolas de “Verão” (2009 e 2010). Foram analisadas as character sticas número de fileiras por espiga, número de grãos por fileira de espiga, prolificidade de plantas e produtividade média total de espigas despalhadas, cujos valores médios foram submetidos à análise de variância conjunta. No ano de 2009 para Tropical Plus e no de 2010 para RB-6324, a prolificidade reduziu linearmente até a máxima população de plantas utilizada, na qual apresentaram os valores de 1,04 espiga planta-1 e 1,02 espiga planta^(-1), respectivamente. Um mínimo valor de prolificidade (1,08 espiga planta^(-1)) foi observado para RB-6324 no ano de 2009 com 92.935 plantas ha-1. Em 2009, as maiores produtividades de espigas despalhadas de Tropical Plus (8,43 t ha^(-1)) e RB-6324 (9,88 t ha^(-1)) foram atingidas com a densidade de 100.000 plantas ha^(-1). Por sua vez, no segundo ano agrícola, as produtividades aumentaram quadraticamente de 51.848 plantas ha^(-1) (7,78 t ha^(-1)), para Tropical Plus, e de 57.648 plantas ha^(-1) (9,32 t ha^(-1)), para RB-6324, até a máxima população de plantas avaliada, em que apresentaram seus respectivos máximos valores de 12,04 t ha^(-1) e 12,31 t ha^(-1). De maneira geral, o incremento populacional foi desfavorável à prolificidade de plantas, porém não prejudicou a produtividade de espigas despalhadas, para a qual se notou melhores respostas com a população de 100.000 plantas ha^(-1), em ambos os anos agrícolas e híbridos utilizados.