Physiological effects of mercury-contaminated Oxisols on common bean and oat.

The heavy metal mercury (Hg) is one of the most complex and toxic pollutants. When present in soils, it may impair plant growth, but the intensity of damage depends on the physical-chemical properties of the soil such as pH, clay, and organic matter content, which in turn affects Hg sorption and bioavailability. Understanding Hg potential damage to staple food crops is of paramount relevance. Here, we evaluated the physiological effects of Hg in Phaseolus vulgaris (common bean) and Avena sativa (oat) cultivated in two Oxisols with contrasting properties: Rhodic Acrudox (RA) and Typic Hapludox (TH). We performed four independent experiments (one per species/soil combination) that lasted 30 days each. Treatments were composed by HgCl2 concentrations in soils (0 to 80 mg kg-1 Hg). At the end of the experiment, we determined the impact of Hg on photosynthesis, nutritional status, and oxidative stress. Cultivation in TH contaminated with Hg resulted in oxidative stress in common bean and decreased photosynthesis/P accumulation in oat. No deleterious effects on physiological variables were detected in both species when cultivated in the RA soil. In general, we conclude that the lower Hg sorption in the TH soil resulted in toxicity-like responses, while acclimation-like responses were observed in plants cultivated in RA, reinforcing soil physical-chemical properties as key features driving Hg toxicity in Oxisols. Graphical abstract.

Adubação fosfatada no desenvolvimento e produção de feijão guandu em latossolo vermelho do cerrado em primeiro cultivo / Phosphorus fertilization on the development and production of pigeonpea in the cerrado oxisol in first cultivation

O fósforo é um importante macronutriente, requerido por todas as plantas para crescimento, desenvolvimento e reprodução, sendo o fator de produção mais importante para a agricultura após a calagem em solos sob vegetação de Cerrado. Assim, objetivou-se avaliar o desenvolvimento e produção do feijão guandu submetido à adubação fosfatada, sem inoculação de sementes, em Latossolo Vermelho do Cerrado em primeiro cultivo. O experimento foi conduzido em casa de vegetação no período de agosto a novembro de 2010. Utilizaram-se vasos contendo 3 dm-3 de solo coletado na profundidade de 0-0,20 m em área de Cerrado. O delineamento experimental foi inteiramente casualizado, com seis doses de fósforo (P2O5): 0; 50; 100; 150; 200 e 250 mg dm-3 em quatro repetições. Houve efeito significativo a 5% de probabilidade para todas as variáveis avaliadas com ajuste aos modelos quadrático e linear de regressão. O melhor desenvolvimento e produção de feijão guandu ocorre no intervalo de doses de fósforo de 162 a 225 mg dm-3. O feijão guandu responde de forma positiva a adubação fosfatada, sem a inoculação de sementes em Latossolo Vermelho do Cerrado em área de primeiro cultivo.

Phosphorus is an important macronutrient required by all plants for growth, development and reproduction, and the most important production factor for agriculture after liming in soils under Cerrado vegetation. Thus, the objective was to evaluate the development and production of pigeonpea subjected to fertilization without inoculation of Cerrado Oxisol in first cultivation. The experiment was conducted in a greenhouse in August-November 2010. We used 3 dm3 pots containing soil collected at 0-20 cm depth in the Cerrado. The experimental design was completely randomized design with six levels of phosphorus (P2O5): 0; 50; 100; 150; 200, e 250 mg dm-3 with four replications. There was a significant effect at 5% probability for all variables adjusted for the quadratic and linear regression. The best development and production of pigeonpea occurs within phosphorus levels of 162 the 225 mg dm-3. The pigeonpea respond positively to fertilization, without the inoculation of seeds in the soil of the Cerrado in first cultivation area.