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Objective: To evaluate the effect of the incorporation of Crotalaria juncea L. as green manure on the weed community in a cassava crop in Tabasco. Design/methodology/approach: The study was carried out in the Experimental Field of Colegio de Postgraduados, Campus Tabasco (18° 01' N and 93° 03' W). The samplings were made on four dates: 1) at the planting of crotalaria (12/03/2018); 2) at flowering (31/01/2019); 3) 20 days after incorporation (22/02/2019); 4) at cassava harvest (25/04/2019), using metal squares 50×50 cm. Two planting densities, 50 and 80 cm (16,600 and 10,375 plants ha-1), two doses of NPK fertilization (160-40-80 and 00-40-80+GM), and a control were tested. The name of the species, number of individuals and coverage (percentage) were recorded to calculate the richness (S), Shannon diversity (H') and uniformity (E) indices, and the importance value index (IVI). Results: The weed community consisted of 32 species, 28 genera and 16 families, of which the best represented are: Convolvulaceae, Asteraceae, Cyperaceae and Poaceae. The most frequently recorded species are Lindernia crustacea, Ludwigia octovalvis, and Ageratum houstonianum. The diversity indices reflected a poor community, especially with GM treatments; diversity ranged from low to medium and uniformity from medium to high. The importance of the families was more related to the environmental conditions than to the treatments; Cyperaceae were more important in the rainy season and Asteraceae in the dry season. L. crustacea appeared throughout the cycle. Limitations/implications: It is advisable to extend the investigation period. Findings/conclusions: The weed flora consisted of 32 species; the Convolvulaceae family was the most diverse and L. crustacea was the most recorded species during the cycle. The diversity indices reflected a poor community. The importance of the families was related to environmental conditions, where Cyperaceae stood out in the rainy season and Asteraceae in the dry season. [ABSTRACT FROM AUTHOR]

Objective: To characterize black and red mangrove ecosystems in the coastal zone of Paraíso, Tabasco, Mexico. Design/Methodology/Approach: Four plots were randomly established in each mangrove ecosystem. Inside each plot, trees were counted per transect, and measured for basal area, diameter at breast height, plant cover and height. Seven diametric classes were estimated to calculate the relative species richness and the dynamics of emergence/disappearance in the ecosystem. Soil samples were surveyed at two depths and during different seasons (dry and rainy). The samples were tested for organic matter (OM), nitrogen content (N), phosphorus (Olsen P), pH, exchangeable bases and humic and fulvic acids; with the objective to characterize nutrient flux dynamics between seasons and compare the two mangrove ecosystems. Results: Red mangrove ecosystems contain higher OM during rainy season. Black mangrove ecosystems showed low contents of OM and exchangeable bases during dry season. The species with more individuals m-2 is red mangrove, and black mangrove presents individuals with greater basal area and diameters. Study Limitations/Implications: Regional characterization of mangrove ecosystems provides information about nutrient flux, which is necessary for the adequate proposal of protection and conservation programs of these wetlands. Findings/Conclusions: The dominant mangrove species affects nutrient flux in soils associated to the ecosystem, suggesting they have specific functions in the ecosystem dynamics. [ABSTRACT FROM AUTHOR]

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Purpose: To identify occupational risks and practices in the four aerial fumigation facilities in the Sierra banana growing region and to evaluate environmental impacts from Mancozeb use. Methods: Occupational health risks were identified and practices in the four aerial fumigation facilities in the Sierra banana growing region were documented. Semi-structured interviews were conducted with installation managers. To evaluate environmental impact, samples of water and soil were collected and analysed in an acute toxicity bioassay with Vibrio fischeri, using uncontaminated soil and water to establish background levels. Results: Even in the largest and best-equipped facility, serious risks to workers' health were encountered from inadequate use of protective equipment by workers. Furthermore, excessive use of pesticide, lack of re-use of unused product, poor facility design and poor use of wash-water were observed, resulting in maximum toxicity of > 5 times background in discharged water. Parallel soil samples were > 20 times more toxic than background, being most toxic at > 0.5 km from the discharge point. Conclusion: Areas of opportunity to improve worker health and the environment include proper and consistent use of protective equipment, re-use of unused product, wastewater reduction and appropriate wastewater treatment. [ABSTRACT FROM AUTHOR]