For climate change scenarios, there is a high degree of complexity, with impacts on the future availability of water resources. In this context, studies related to changes in rainfall time series are essential in order to identify environmental vulnerability. The objective of this study was to analyze trends in the rainfall regime, number of rainy days and temperature for stations located at different continentality and altitude conditions in Northeast Brazil. Meteorological data of the Instituto Nacional de Meteorologia were used, being classified according to the location in relation to the continent: coastal strip (14 stations), strip of 150-300 km up to 300 m altitude (14 stations) and above 300 m (five stations), between 400 and 600 km from the coast up to 300 m (four stations) and above 300 m (eight stations). All the 45 stations used have a historical series with a data period of more than 30 years. The trend of rainfall and rainy days was obtained through the Mann-Kendall and regression analyses, at significance levels of 0.01 and 0.05, respectively. There were trends of reduction in the number of rainy days, in the coastal strip, as well as reduction in rainfall and rainy days, both in the strip of 150-300 km from the coast and in the Sertão region, with no significant effect of continentality in the strip of 400-600 km from the coast. For temperature, except for Maceió, AL, Brazil, there is a trend of increase in near future.
A B S T R A C TThe present study evaluated soil moisture (θ) in forage cactus plantations under resilience practices such as irrigation, mulching and intercropping with sorghum. The experiment was arranged in a randomized block design with five water availability conditions (0, 8.75, 17.5, 26.25 and 35% of the reference evapotranspiration), and three planting systems: forage cactus exclusive system (PE), forage cactus with mulch (PC) and intercropping between forage cactus and sorghum (PS). Water content was measured until a depth of 0.60 m. Meteorological data were recorded between June 2012 and June 2013. Water content was not affected by different resilience practices and the variation coefficient was low to medium (4.0 to 22.1%). The temporal variation of soil moisture was more affected by the changes in rainfall, while the physical properties (soil density, porosity and grain size) were decisive in the vertical variation. It was concluded that periods with rainfall events favor the alternation of practices to improve forage cactus resilience (irrigation, mulch and intercropping).Umidade do solo em lavouras de palma forrageira com práticas de melhoria da sua resiliência R E S U M ONo presente estudo a umidade do solo (θ) foi avaliada em lavouras de palma forrageira sob práticas resilientes, tais como irrigação, cobertura morta e consórcio com a cultura do sorgo. O experimento foi disposto em blocos ao acaso com parcelas de cinco condições de disponibilidade hídrica (0, 8,75, 17,5, 26,25 e 35% da evapotranspiração de referência) e subparcelas de três sistemas de cultivo: palma exclusiva (PE), palma com cobertura morta (PC) e consórcio palma-sorgo (PS). O monitoramento da umidade do solo foi feito até a profundidade de 0,60 m. Dados meteorológicos foram registrados entre junho de 2012 e junho de 2013. A umidade do solo não foi afetada pelas diferentes práticas para melhoria da resiliência e o coeficiente de variação foi de baixo a médio (4,0 a 22,1%). O aumento das lâminas de água, cobertura morta e as camadas mais profundas do solo promoveram menores variabilidades da θ. A variação temporal da umidade foi mais afetada pelas alterações da precipitação enquanto as propriedades físicas (densidade do solo, porosidade e frações granulométricas) foram decisivas na variação vertical. Conclui-se que períodos com ocorrência de eventos de chuva favorecem a alternância de práticas de melhoria da resiliência da palma forrageira (irrigação, cobertura morta e consórcio).
Abstract. Hydrological studies in small basins are essential for investigating the role of distinct processes on water resources conservation and to assess the impact of the natural ecosystems on improving water security especially in semiarid environments. In Brazil, the cooperative hydrological Network REHISA (“REde de HIdrologia do SemiÁrido”) comprises hydrologists from several universities of Brazil, focusing on field measurements, monitoring and modeling activities in well instrumented experimental rural catchments located at different regions and biomes in Semiarid environment. Water scarcity is a common aspect among the catchments, as well as risks of soil and water degradation. The objective of this work is to present assessments of near surface soil moisture spatial-temporal distribution, and to evaluate the impact of soil conservation techniques in reducing runoff, using small-scale experimental plots in a representative catchment of the Pernambuco State, Brazil. The study catchment is located in Alto Ipanema River Basin (AIRB) (with an area of 150 km2), which is located at the semiarid region of the São Francisco River (area of 641 000 km2). Soil and water monitoring was performed in experimental plots with different soil cover conditions (Bare soil plots; Plots with natural cover – Caatinga Biome vegetation; Plots with cactus Palma barriers; and Plots with mulch cover – Dry grass mulch at 4 t ha−1), where probes were installed for high resolution soil moisture assessment. In addition, regular soil moisture monitoring campaigns were conducted at 7 different locations, using a capacitance probe, with arboreal and shrub Caatinga vegetation, pasture and bare soil, predominantly Brachiaria decumbens. Mulch cover runs close to the Caatinga cover, but still with higher runoff generation, and presenting lower soil moisture temporal mean values. Caatinga was highly effective in terms of soil and water conservation at the small basin scale for both the dry and the wet season, resulting in a positive nexus between vegetation and water availability at the region.
A escassez de água no semiárido pernambucano, associada à necessidade de produção agrícola contribuem para uso de efluentes domésticos tratados para fins hidroagrícolas. No entanto, para intensificação do reuso de água são necessárias ações de gestão participativa, principalmente aos jovens do meio rural, incentivando a permanência no campo. O estudo objetiva avaliar a viabilidade de cultivos agrícola com o reuso de efluente doméstico tratado, associado a práticas de conservação de água e solo, no semiárido. Desta forma, este estudo apresenta resultados de produção de milho, girassol e sorgo irrigado com esgoto doméstico tratado, com participação de agricultores rurais e jovens locais. O estudo foi desenvolvido na Estação de Tratamento de Efluentes (ETE) localizada no Distrito de Mutuca, Pesqueira-PE. O plantio do milho (Zea mays L.), realizado em 2016, e do girassol (Helianthus annuus L.), em 2017, foram realizados em duas parcelas experimentais, uma sem e outra com lodo de esgoto (LE), e o sorgo (Sorghum sudanense (Piper) Stapf) foi cultivado em 2019, com e sem cobertura morta (CM) (capim natural). O monitoramento agrometeorológico foi realizado de forma participativa com moradores e alunos de escola da comunidade local. Constatou-se que a altura das plantas, o diâmetro do caule e o número de folhas foram superiores nos tratamentos em que foram adicionados LE no girassol, e no diâmetro do colmo para o milho e sorgo. As aplicações de LE e CM promoveram incremento da umidade do solo. Através da gestão participativa, ações voltadas à intensificação do uso de efluentes domésticos e lodo de esgoto para fins hidroagrícolas devem ser incentivadas, promovendo a produção de alimentos e aumento de renda aos produtores agrícolas.
A identificação de regiões vulneráveis à desertificação é necessária para o Nordeste brasileiro, que apresenta restrição hídrica e sensibilidade as alterações climáticas. Desta forma, através do Índice de Aridez (IA) é possível identificar estas alterações e os elementos climáticos que mais influenciam para estas mudanças em diferentes localizações geográficas. O objetivo foi identificar os principais elementos climáticos responsáveis pela variação temporal e espacial do IA nos estados da Bahia e Pernambuco por meio da análise multivariada. As localidades estudadas foram Salvador, Lençóis, Bom Jesus da Lapa, Recife, Garanhuns e Cabrobó. Foram calculados os Balanços Hídrico Climatológico, para cada estação, em cada média móvel de 30 anos no período de 1961 a 2015, com o auxílio do Software para o Cálculo do Balanço Hídrico de Thornthwaite®. Foi aplicada a análise de agrupamento hierárquica aos dados de séries temporal (S), temperatura (T), precipitação (P), evapotranspiração potencial (ETP) e IA. A Bahia passou por mudanças no IA, sendo possível evidenciar que o aumento da temperatura foi o principal elemento climático responsável. Em Pernambuco também foram maiores correlações da série temporal com as temperaturas. S, T e ETP exercem forte correlação para elevação da condição de aridez em todas as localidades estudadas.
Maize crop under rainfed conditions is widely grown in the Brazilian Northeast on community farms for human and animal consumption. The application of mulch could be adopted to enhance rainwater harvesting and soil moisture levels, although such practice is rarely applied in rainfed cultivation. This study aimed to evaluate the spatial variability of maize productivity, based on soil physical attributes and plant growth and yield, under a rainfed regime in the presence and absence of mulch in the Brazilian semi-arid region. The study was conducted from May to September 2016 in Pesqueira - PE (locality of the Semiarid of Pernambuco State, Northeast, Brazil), during which the development and production of maize in experimental plots were evaluated, and maize was grown using the traditional cropping system with and without mulching. Two grids with 40 points in a 4 × 10 m mesh were established, with spacing of 1 m for soil sampling and maize biometric evaluation. For statistical analysis, 30 samples were randomly selected from each plot. Maize cultivated in the presence of mulch showed higher development, with symmetrical distribution for all variables except for soil moisture and stem diameter. Sand content, soil moisture, height of the first cob, number of leaves, leaf length, plant height, and cob weight presented moderate to strong spatial scale dependence for the two cropping conditions, with higher spatial dependence consistently observed for the development parameters in the covered area.
Water scarcity and changing rainfall distribution have caused uncertainties in relation to agricultural production in semiarid areas. In this context, water reuse for irrigation is a promising alternative, although requiring irrigation and agricultural management. Production of forage plants is strategic for semiarid areas due to their high tolerance to stresses and use as animal fodder. The objective of this work was to evaluate the combined performance of treated wastewater irrigation and mulching on forage sorghum and on soil attributes in Northeast Brazil. Sorghum was cropped in November 2018, three months before the beginning of the hydrologic year, and cultivated over three cycles until April 2019. The experiment was designed with five irrigation depths (60%, 80%, 100%, 120%, and 140% of crop evapotranspiration), and with four soil cover conditions (0% (witness), soil covered with native vegetation, with coconut coir, and with macerated moringa seeds), adopting four replications. Irrigation with treated wastewater promoted linear increases in forage sorghum yield at irrigation depths of up to 140% of crop evapotranspiration. Mulch promoted a 24% increase in productivity in relation to the area where conservation was not practiced, being able to control salinity while also contributing to the higher incorporation of organic matter. Irrigation with treated wastewater had no negative agronomic impacts on soil, once natural rainfall events typical of the Brazilian semiarid region allowed effective salt leaching from shallow sandy soils.
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