The soil attributes controlling the CO2, and CH4 emissions were assessed in semiarid mangrove soils (NE-Brazil) under different anthropogenic activities. Soil samples were collected from different mangroves under different anthropogenic impacts, e.g., shrimp farming (Jaguaribe River); urban wastes (Cocó River) and a control site (Timonha River). The sites were characterized according to the sand content; physicochemical parameters (Eh and pH); total organic C; soil C stock (SCS) and equivalent SCS (SCSEQV); total P and N; dissolved organic C (DOC); and the degree of pyritization (DOP). The CO2 and CH4 fluxes from the soils were assessed using static closed chambers. Higher DOC and SCS and the lowest DOP promote greater CO2 emission. The CH4 flux was only observed at Jaguaribe which presented higher DOP, compared to that found in mangroves from humid tropical climates. Semiarid mangrove soils cannot be characterized as important greenhouse gas sources, compared to humid tropical mangroves.

O objetivo deste trabalho foi avaliar, em casa de vegetação, os efeitos de doses de esterco bovino e de calcário na formação de mudas de guanandi (Calophyllum brasiliense Cambèss.). Foram avaliadas quatro doses de cada fator, combinadas em esquema fatorial 4x4. O delineamento experimental foi inteiramente ao acaso com quatro repetições, e cada parcela continha cinco mudas. O substrato foi formado pela mistura, em volume, de oito partes de subsolo e duas partes de areia, e doses de esterco correspondentes a 0, 2, 4 e 6 partes que, em massa, equivalem a 0, 101, 175 e 229 kg m-3. As doses de calcário foram calculadas para elevar a saturação por bases (V%) a 20, 35, 50 e 65%. Aos 120 dias, foram avaliados: altura, diâmetro do colo, número de folhas, área foliar e matéria seca das partes aérea e radicular das mudas. Em substrato constituído de subsolo+areia, a calagem e a adubação com esterco bovino não são necessárias para produção de mudas de guanandi.

Barium has been identified as a toxic element to most plants, although for grasses the toxicity has not been determined. A greenhouse experiment was performed to evaluate the effect of barium on growth parameters, barium accumulation, and macronutrient concentration in Tanzania guineagrass (Panicum maximum Jacq.), cultivated in nutrient solution. Five barium rates and a control were set in a complete randomized block design, with four replications. Forage yield, leaf area, barium, and macronutrient concentrations and accumulation were measured. Leaf area and yield sharply decreased with increase of barium concentration in the nutrient solution. The greatest barium concentration and accumulation were found in culms and sheaths. Toxic barium concentrations were estimated to be 1.24 mmol L⁻¹ (170 mg L⁻¹) in nutrient solution and 225 mg kg⁻¹ in the diagnostic leaf, and the main symptoms of toxicity were interveinal chlorosis followed by necrotic spots in the leaf laminae of the grass.