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Nickel availability on soil-plant system: effects of Ni rates and saturations base

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Fernando Giovannetti de Macedo
Total Authors: 1
Document type: Doctoral Thesis
Press: Piracicaba.
Institution: Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura
Defense date:
Examining board members:
José Lavres Junior; Edson Lazarini; Paulo Sergio Pavinato; Tiago Tezotto
Advisor: José Lavres Junior; Wilson Tadeu Lopes da Silva

As an essential element for plants and a heavy metal at the same time, nickel requires attention on the aspects of the physiology of plants and environmental. Furthermore, there is a narrow range between nutritional requirements and toxic levels to plants. In this context, the aim was to evaluate the effect of Ni in soil-plant system through experiment under controlled conditions, using soil pots distributed entirely at random, using a factorial 2 x 5, with seven repetitions each treatment. The first factor was formed of two saturations base (50 and 70%) and the second of five Ni rates (0, 0.1, 0.5, 1.0 and 10.0 mg dm-3 of soil). The pots were filled with 8 dm3 of soil and sown with soybean [Glycine max (L.) Merrill] succeeded by sunflower (Helianthus annuus L.). The agronomic traits: plant height (PH), stem diameter (SD), number of nodes (NN), phenological stage (PS), SPAD index, head diameter (HD) (Sunflower) were evaluated at 30 and 60 days after emergence (dae) of each crop. Whole soybean plants, sampled in four pots of each treatment were collected at the R1 stage for analysis of soil samples from the rhizosphere. Then, the collected plants were divided into: sheets; roots (nodules on soybean) and shoot. Were determined in the leaves used for diagnosis in soybean and sunflower: macro and micronutrients, activities of nitrate reductase, and urease and concentrations of organic acids: oxalic, malonic, succinic, malic, tartaric, fumaric, oxaloacetic, citric and lactic. The same organic acids were determined in secondary roots of sunflower and nodules of soybean. They were conducted ultrastructural evaluations by means of transmission electron microscopy (TEM) in sunflower roots, and color in soybean nodules, using light microscopy. In the soil were determined: urease activity dehydrogenase, the total Ni and available by methods: Mehlich-1, Mehlich-3 and DTPA. At physiological maturity period of each culture was performed to harvest the plants of other pots in order to determine grain dry matter yield, Ni content in the whole plant and Ni and N content in grains. At the end of the two experiments it were carried out new soil sampling for Ni sequential extraction. The SPAD index taken on soybean leaves at 60 d.a.e., the dry matter production of the aerial part of soybean and sunflower root were influenced by the base saturation, nickel doses and the interaction among them. They were influenced by the saturation for base and nickel doses (single factor): soybean: HP d.a.e. to 60, NN at 30 and 60 d.a.e., SPAD to 30 d.a.e.; Sunflower: PH and NN at 30 and 60 d.a.e., HD and SPAD to 30 d.a.e. The other variables assessed at 30 and 60 d.a.e. They were influenced only by base saturation, or Ni doses separately. Sunflower soybean plants had higher Ni contents at the different tissues (except grain) when grown under V50%. The production of soybean and sunflower grains was not affected by the treatments, but the N content of the soybeans was changed by Ni rates V70%. The urease enzyme activity in soybean and sunflower leaves was responsive to increased doses of Ni. Four of the organic acids and the N content in leaves and grains were higher in plants grown under V70% at the dose of 0.5 mg dm-3 Ni. Ni rates as well as the cation base saturation directly influenced the balance of plant nutrients. The Mehlich-1, Mehlich-3 and DTPA presented higher coefiencient correlation between available Ni soil fraction with nutrient concentrations in both soybean and sunflower, with the DTPA solution showing the highest correlation coefficient in this analysis. Ni showed variable distribution among different soil fractions in the treatments. The treatments presented soil under cation bases saturation of 70% showed higher Ni concentration linked to carbonate, as compared to treatments under cation base saturation of 50%. The distribution of Ni between the soil fractions followed the following order: bound to carbonate <exchangeable < bound to oxides <organic matter <residual. The cation base saturation showed different effects on the urease activity according to the plant evaluated. Ni exerted on the differential effect dehydrogenase activity according to the plant specie (AU)

FAPESP's process: 12/18226-2 - Nickel availability in soil-plant system: effect of rates and basis saturation levels
Grantee:Fernando Giovannetti de Macedo
Support type: Scholarships in Brazil - Doctorate