Although the information on the Normalized Difference Vegetation Index (NDVI) in plants under water deficit is often obtained from sensors attached to satellites, the increasing data acquisition with portable sensors has wide applicability in agricultural production because it is a fast, nondestructive method, and is less prone to interference problems. Thus, we carried out a set of experiments to investigate the influence of time, spatial plant arrangements, sampling size, height of the sensor and water regimes on NDVI readings in different soybean cultivars in greenhouse and field trials during the crop seasons 2011/12, 2012/13 and 2013/14. In experiments where plants were always evaluated under well-watered conditions, we observed that 9 a.m. was the most suitable time for NDVI readings regardless of the soybean cultivar, spatial arrangement or environment. Furthermore, there was no difference among NDVI readings in relation to the sampling size, regardless of the date or cultivar. We also observed that NDVI tended to decrease according to the higher height of the sensor in relation to the canopy top, with higher Electronic supplementary material The online version of this article (values tending to be at 0.8 m, but with no significant difference relative to 1.0 m-the height we adopted in our experiments. When different water regimes were induced under field conditions, NDVI readings measured at 9 a.m. by using a portable sensor were successful to differentiate soybean cultivars with contrasting responses to drought.

The development of drought tolerant plants is a high priority because the area suffering from drought is expected to increase in the future due to global warming. One strategy for the development of drought tolerance is to genetically engineer plants with transcription factors (TFs) that regulate the expression of several genes related to abiotic stress defense responses. This work assessed the performance of soybean plants overexpressing the TF DREB1A under drought conditions in the field and in the greenhouse. Drought was simulated in the greenhouse by progressively drying the soil of pot cultures of the P58 and P1142 lines. In the field, the performance of the P58 line and of 09D-0077, a cross between the cultivars BR16 and P58, was evaluated under four different water regimes: irrigation, natural drought (no irrigation) and water stress created using rain-out shelters in the vegetative or reproductive stages. Although the dehydration-responsive element-binding protein (DREB) plants did not outperform the cultivar BR16 in terms of yield, some yield components were increased when drought was introduced during the vegetative stage, such as the number of seeds, the number of pods with seeds and the total number of pods. The greenhouse data suggest that the higher survival rates of DREB plants are because of lower water use due to lower transpiration rates under well watered conditions. Further studies are needed to better characterize the soil and atmospheric conditions under which these plants may outperform the non-transformed parental plants.

; Alexandre do Rio 3 ResumoNas pulverizações agrícolas geralmente é dada muita importância aos produtos fitossanitários e pouca à técnica de aplicação, sendo que as perdas podem ultrapassar 70% do total aplicado. A alta temperatura e a baixa umidade relativa do ar têm importante efeito sobre a pulverização de produtos fitossanitários, causando evaporação mais rápida das gotas. O objetivo deste trabalho foi avaliar a variação da deposição da calda de pulverização com três tipos de pontas (jato cônico vazio, jato plano e antideriva) nas diferentes horas do dia. Uma solução salina foi aplicada em copos de PVC, aos quais, foram adicionados água destilada e deionizada, para leitura da condutividade elétrica. De maneira geral as pontas de pulverização de jato plano e antideriva não tiveram a deposição afetada pela variação da temperatura e umidade relativa do ar e não diferiram entre si, mas o mesmo não ocorreu com a ponta de jato cônico vazio onde a variação foi de mais de 100%. Os resultados mostraram que a deposição das gotas produzidas pela ponta de jato cônico vazio foi significativamente afetada pela variação das condições meteorológicas. Palavras-chave: Produto fitossanitário, temperatura, umidade relativa, tecnologia de aplicação AbstractIn the agricultural sprays more importance is generally given to the pesticide and less to the application technique, though the losses can overpass 70%. The high temperature and the low relative humidity of the air have important effects on the spraying of pesticides, causing faster evaporation of the drops. The objective of this research was to evaluate the variation of the deposition spray with three types of nozzles in different hours of the day (hollow cone, reduced drift and air inclusion). A saline solution was applied in PVC glasses to which distilled water was added for electric conductivity reading. In a general way the deposition of the flat fan nozzles and the anti-drift ones had no difference and was not affected by the variation of the temperature and relative humidity, but the hollow cone nozzle presented variations of more than 100%. The results showed that the hollow cone deposition was significantly affected by meteorological conditions variations.

ABSTRACT:The climate and its variability is the main risk factor for the success of soybean crop in southern Brazil. Such aspect becomes even more important under the future climate scenarios, in which global warming is expected. Based on that, the objectives of this study were to identify the impacts of raising temperatures on soybean yields in southern Brazil and how management strategies represented by changing sowing dates could be able to mitigate them. The soybean yields for the present and future scenarios were estimated by the crop simulation model CROPGRO-Soybean calibrated for southern Brazil. The simulations were done for 13 locations distributed in the states of Paraná, Santa Catarina and Rio Grande do Sul, considering climatic series of 31 years. The future climate scenarios were built based on downscaling temperature changes from ETA and PRECIS models for the periods: 2013-2043 (D25) and 2041-2071 (D55), without considering the increase in the atmospheric CO 2 concentration. The soybean potential (Y p ) and attainable (Y a ) yields and their relationship (Y a /Y p ) were estimated for all scenarios and used to determine the climatic risk for the crop. In order to investigate how to mitigate the global warming impacts on soybean yields, different sowing dates, two earlier and two later than the present recommendation, were simulated in the crop model and resulting yields were compared. In general, raising temperature will lead soybean crop in southern Brazil to lower yields, for both Y p and Y a , with higher impact on Y a , independently of the climate model used. Also, the climatic risk for the crop will increase in the future climates scenarios. The strategy of changing the sowing date showed to be feasible to reduce the impacts of raising temperatures on soybean yields, but only when it is delayed in relation to the sowing period presently recommended for this crop in the region.