The objective of this work was to evaluate seeds of cowpea, cultivar BRS Tumucumaque, subjected to different water stresses induced by polyethylene glycol (PEG-6000) and mannitol and different salt stresses induced by NaCl and CaCl2 solutions. The water and salt stresses was evaluated in laboratory using completely randomized experimental designs in 2x6 factorial arrangements, with six osmotic potentials (0.0, -0.2, -0.4, -0.6, -0.8 and -1.0 MPa) and two stress inducers for each experiment, with four replications of 50 seeds. The percentage of germination, germination speed index, root and shoot lengths and seedling fresh weight were evaluated at the tenth day (end of the evaluation period). The simulated water stress showed effects on the cowpea seed germination and seedling initial growth by decreasing the rates of the variables evaluated, which had greater effect in treatments with PEG-6000. The salt stress induced by NaCl showed greater effect on the variables evaluated than that induced by CaCl2, due to the sodium toxicity in the salt chemical composition.

O tipo, modo de ação e época em que o dessecante é aplicado na cultura da soja, são fatores que podem afetar a qualidade fisiológica das sementes. Porém, se a aplicação for realizada de maneira adequada, poderá ocorrer antecipação da colheita em alguns dias, obtendo sementes de maior qualidade. Assim, o presente trabalho teve como objetivo verificar o efeito da dessecação em pré-colheita no desempenho fisiológico de sementes de soja. O delineamento experimental foi de blocos ao acaso em esquema fatorial 3 x 4 (dessecantes x épocas) com quatro repetições. Os dessecantes foram Diquat e Paraquat, ambos na dose de 400 g i.a. ha^-1, + testemunha (sem dessecação). As épocas de aplicação foram nos estádios R6.0, R7.1, R7.2 e R7.3. As sementes foram submetidas ao teste de germinação, primeira contagem da germinação, índice de velocidade de germinação, envelhecimento acelerado, teste de frio e condutividade elétrica. Todos os testes foram realizados no Laboratório de Análise e Tecnologia de Sementes da Universidade do Estado de Mato Grosso. A análise de variância foi realizada, sendo os dessecantes comparados pelo teste de Tukey (p<0,05). Apesar de terem proporcionado antecipação da colheita em apenas dois dias em relação à testemunha, a época mais favorável à dessecação, tanto com Diquat quanto Paraquat, é no estádio R7.3, sendo que os lotes dessecados com Paraquat apresentou melhor desempenho em alguns dos testes de qualidade avaliados.

The proper soil use and management are essential for a sustainable production, thus the pursuit for systems that minimize damages to the environment and improve soil fertility is continuous. The objective of this study was to evaluate changes in soil fertility by the use and management of an Oxisol (Latossolo Vermelho-amarelo, SiBCS) in the Amazon biome. The soil uses and management systems evaluated were native forest, native pasture, minimum tillage system and conventional tillage system. The chemical atributes of the soil layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m were evaluated. The soil pH (CaCl2) and the contents of organic matter, available phosphorus and exchangeable potassium, calcium, magnesium and aluminum were evaluated and the saturation by Al, effective cation exchange capacity and soil potential were determined. The highest pH values were found in the native pasture area, and the highest exchangeable aluminum contents were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest phosphorus availability was found in the layer 0.00-0.10 m of the native forest area. The highest potassium availability was found in the minimum tillage system. The lowest calcium and magnesium values were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest soil organic matter content was found in the layer 0.00-0.10 m of the native forest area. The nutrient availability for plants decreases in soils managed using the conventional tillage system. Soil uses and management systems of little soil disturbance are recommended to minimize environmental degradation in the Amazon biome.

Deforestation may have effects on the hydrological cycle, directly reflecting in the rainfall rates. Therefore, studies pointing out evidence of climate changes caused by deforestation are extremely important, because they help understanding the way how these changes are related to forms of using and occupying the territory, as well as to the way how information obtained can to be useful for mitigating their effects. In this context, this paper aimed to analyze rainfall variations occurring in the municipality of Colíder, Mato Grosso, southern Amazon,Brazil, within a temporal scale of 28 years (daily data), correlating them to the regional and local deforestation patterns by determining Spearman's ρ coefficient. Annual rainfall presented a large variation, with a minimum of 1,296 mm in 1987 and a maximum of 2,492.8 mm in 1990. The rainy season was concentrated between October and April, and the driest period was within June and August. Spearman's coefficient pointed out negative correlations between regional and local deforestation and local rainfall, showing that the larger the deforested area, the lower the rainfall rate observed.

Global climate change is closely tied to CO₂ emissions, and implementing conservation-agricultural systems can help mitigate emissions in the Amazon. By maintaining forest cover and integrating sustainable agricultural practices in pasture, these systems help mitigate climate change and preserve the carbon stocks in Amazon forest soils. In addition, these systems improve soil health, microclimate regulation, and promote sustainable agricultural practices in the Amazon region. This study aimed to evaluate the CO₂ emission dynamics and its relationship with soil attributes under different uses in the Amazon. The experiment consisted of four treatments (Degraded Pasture—DP; Managed Pasture—MP; Native Forest—NF; and Livestock Forest Integration—LF), with 25 replications. Soil CO₂ emission (FCO₂), soil temperature, and soil moisture were evaluated over a period of 114 days, and the chemical, physical, and biological attributes of the soil were measured at the end of this period. The mean FCO₂ reached values of 4.44, 3.88, 3.80, and 3.14 µmol m⁻² s⁻¹ in DP, MP, NF, and LF, respectively. In addition to the direct relationship between soil CO₂ emissions and soil temperature for all land uses, soil bulk density indirectly influenced emissions in NF. The amount of humic acid induced the highest emission in DP. Soil organic carbon and carbon stock were higher in MP and LF. These values demonstrate that FCO₂ was influenced by the Amazon land uses and highlight LF as a low CO₂ emission system with a higher potential for carbon stock in the soil.