Resumo

PADUA JUNIOR, Alceu L; ABREU, Cleide Aparecida de; FURLANI, Pedro Roberto  e  ABREU, Mônica F de. Copper availability determination in substrates. Hortic. Bras. [online]. 2008, vol.26, n.2, pp. 202-208. ISSN 0102-0536.  http://dx.doi.org/10.1590/S0102-05362008000200015.

To improve the quality of plants grown under protected or semi-protected environments it is very important to adopt inert or less altered materials to use as soilless media. These materials, called substrates, depending on its origin could be organic, mineral, or synthetic. Among the nutritional problems, the lack or excess of copper (Cu) has been the main factor affecting seedling production. The objective of this research was to evaluate efficient methods to quantify available Cu in substrates. The experiment was conducted under semi-controlled greenhouse conditions with rucula (Eruca sativa L.) as plant-test grown on three substrates (coir, pinus bark, and peat). All the substrates received five Cu doses (0; 0.5; 1.0; 2.0, and 3.0 mg dm^-3). After the plant harvest a substrate sample was collected to extract Cu by the following methods: DTPA at pH 2.6, DTPA + triethanolamine at pH 7.3, HNO₃ + H₂O₂ at 30%, K₄P₂O₇, and NaOCl at pH 8.5 + DTPA. The acid solutions presented higher Cu extractive capacity for all tested substrates. Among the substrates, only the coir presented statistically significant values of R² for all the extraction methods. However, when the substrates were analyzed together, all methods presented statistically significant regression coefficients (R²) higher than 0.51, indicating that all the extraction methods can be used to quantify available Cu on these substrates.

Palavras-chave : extracting agents; chemical analysis; micronutrient; coir; pinus bark, and peat.