RESUMOPropôs-se, neste trabalho, avaliar as condições climáticas atuais da região Nordeste do Brasil e elaborar os cenários climáticos para os anos de 2050 e 2100. Utilizaram-se as séries temporais da temperatura do ar média correspondentes ao período de 1961 a 2007, e as médias climatológicas de precipitação pluvial de 89 localidades no Nordeste do Brasil. O teste não-paramétrico de Mann-Kendall foi empregado para avaliar o nível de significância das tendências das séries temporais da temperatura do ar média e o "software" SEVAP, para obtenção da evapotranspiração potencial anual e dos índices de aridez, umidade e hídrico. Os resultados obtidos indicam tendências crescentes nas séries temporais de temperatura do ar, estatisticamente significativas pelo teste de Mann-Kendall, tanto para o período estudado como para os cenários de 2050 e 2100. As maiores taxas de aumento das temperaturas do ar médias anuais foram encontradas para a situação climática atual e para o cenário do ano de 2050, e menor aumento de seus valores entre os cenários de 2050 e 2100. Os índices de aridez e hídrico indicam aumentos enquanto o índice de umidade mostra redução nos cenários estudados, principalmente na parte semiárida da região. Palavras-chave: evapotranspiração potencial, índice de aridez, teste de Mann-KendallStudy of some climate scenarios for the northeastern region of Brazil ABSTRACTThe main objective of this study is to assess the current climatic conditions in northeastern region of Brazil and to obtain some climatic scenarios for the years 2050 and 2100. Time series of mean air temperature and rainfall from 1961 to 2007 period and 89 stations in the study region were used. The non-parametric test of Mann-Kendall was used to assess the statistical significance level of the analyzed time series. Also, the software SEVAP was used to determine potential evapotranspiration, humidity index, aridity index and water index. Results showed an increasing trend in the time series of air temperature, which were statistically significant by the Mann-Kendall test, for the current period and for the 2050 and 2100 scenarios. Mean air temperature has its highest rate for the current period and for the 2050 scenarios and a reduced increase between the 2050 and 2100 scenarios. The aridity and water indexes indicated an increase while the humidity index showed a reduction for two analyzed scenarios in northeastern region of Brazil, principally in the semiarid area.

RESUMOA finalidade deste trabalho é avaliar as tendências das séries temporais do saldo radiação no Nordeste do Brasil, através de dados de reanálise do NCEP/NCAR referentes ao período de 1948 a 2006. As séries temporais anuais de dados observados na superfície de radiação solar global e evaporação do tanque classe "A" de duas localidades do semiárido da região de estudo, também foram utilizadas. Analisou-se a variabilidade temporal das séries temporais com base no teste não-paramétrico, de Mann-Kendall. As séries temporais do saldo de radiação exibiram reduções acentuadas entre 1948 e 1987, que foram estatisticamente significativas em níveis de 0,01 de probabilidade pelo teste de Mann-Kendall; verificou-se, entretanto, no período de 1988 a 2006, comportamento inverso, predominando tendências positivas de saldo de radiação. Os resultados também indicaram que os dados observados de radiação global e de evaporação do tanque classe "A", apresentam reduções acentuadas ao longo do período estudado estatisticamente significativos em níveis de 0,01 de probabilidade. Esses resultados sugerem a presença do fenômeno "Global dimming" sobre a região Nordeste do Brasil. Palavras-chave: evaporação do tanque classe "A", global dimming, teste de Mann-Kendall Study of the variability of solar radiation in northeast Brazil ABSTRACTThe main objective of this work was to assess the tendency of time series of net radiation in the northeastern region of Brazil from the NCEP/NCAR database of the 1948-2006 period. Also, the annual time series of data observed at surface of global solar radiation and class A pan evaporation for two stations located in the semiarid area of studied region were analyzed. Long-term variability of the time series was assessed by the Mann-Kendall test. The time series of net radiation showed a reduction through the 1948-1987 period, statistically significant at the 0.01 level of probability by the MannKendall test. However, the 1988 to 2006 period showed an inverse pattern in net radiation with positive trends. Results also indicate that observed data in global solar radiation and class A pan evaporation at Petrolina, PE and Juazeiro, BA presented an accentuated decrease through the study period statistically significant at 0.01 level of probality by the MannKendall test. These results suggest that the global dimming effect is present in the northeastern region of Brazil.

This study aimed to evaluate the behavior of soybean plants subjected to irrigation management with controlled water deficits in different phenological stages. The research was conducted in an experimental area of the Federal University of Tocantins (UFT), in Palmas-TO, Brazil. The experimental design was randomized blocks with four replicates, and treatments arranged in a split-plot scheme. The plots consisted of irrigation levels that induced plants to water deficit in the vegetative stage, reproductive stage and throughout the entire cycle, based on potential crop evapotranspiration (ETpc). The subplots corresponded to two soybean cultivars (M9144RR and TMG1288RR). The following agronomic variables were evaluated: days until flowering, days until maturation, plant height, first pod height, number of pods per plant, stem diameter, leaf area and yield. Irrigation management with moderate water deficit, 50% of ETpc, in the vegetative stage, promoted the best agronomic characteristics and contributed to increase the yield of the evaluated soybean cultivars, especially M9144RR.

This study aimed to verify the effect of co-inoculation, association between Azospirillum brasilense and Bradyrhizobium japonicum bacteria, on soybean plants subjected to water deficit at two sowing dates. Two field experiments were conducted at the Universidade Federal de Tocantins, campus of Palmas, Brazil, in 2016. The experimental design was randomized blocks in a split-split-plot arrangement with four repetitions, where the plots consisted of two irrigation depths (100 and 25% of crop evapotranspiration - ETc), the subplots was composed of two methods of inoculant application (inoculation with Bradyrhizobium japonicum and co-inoculation with Azospirillum brasilense + Bradyrhizobium japonicum) and the sub-subplots comprised two soybean cultivars (TMG 132 and ANTA 82). The cultivars responded differently to the sowing dates. Co-inoculation did not influence grain yield under full irrigation conditions (100% ETc), in neither cultivar evaluated. However, under the water deficit condition (25% ETc), the grain yield of the cultivar TMG 132 increased 77.20%, indicating that there are different responses of interaction between Azospirillum brasilense, plant genotype and sowing dates.

The climatic conditions along the cycle are the main factors responsible for the final production of any crop. This study aimed to evaluate the current conditions and the effects of climate change scenarios on the yield of soybean grown in the Matopiba region, located between the states of Tocantins, south and northeast of Maranhão, south of Piauí and west of Bahia, Brazil. The AquaCrop model of FAO, version 5.0, was calibrated with data of 2014 and validated with those of 2016, using climate, soil and crop management parameters collected in two experimental campaigns conducted between June and October in 2014 and 2016 in Palmas, TO, Brazil. The performance of the model was evaluated using the following statistical indicators: prediction error (PE), coefficient of determination (R2), normalized root mean square error (NRMSE), Nash-Sutcliffe model efficiency coefficient (EF) and Willmott’s index of agreement (d). It was verified that the AquaCrop model underestimates soybean grain yield under severe water stress conditions throughout the growing cycle. The increase in CO2 concentration and in the air temperature, projected by the climate models HadGEM2-ES and MIROC5 under the scenario of stabilization (RCP 4.5) and the scenario of progression (RCP 8.5), have contributed to the increase in soybean yield by the end of this century.