Soil boron determination through the sunflower biological method

Abstract

In order to estimate the available boron status of five soil series found in Piracicaba (SP), a bioassay was conducted with sunflower (Helianthus annus L.) in greenhouse during a period of 54 days. All soils received a nutrient solution which contained macro and micronutrients except boron. Parameters like age value and plant height and dry matter yield were determined at several phases of the plant growth at the end of the trial. At the same time, pattern collections of 2 mm seived sillica were submitted to the same treatments applied to the soil samples, besides the following levels of boron: 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0 ppm. The hot water-soluble boron level range in the soils were better reflected by the classification done through the age value and height, than through the dry matter produced by the sunflower plants. Soil series were classified as: a) highly deficient: Paredão-Vermelho; b) moderately deficient: Quebra-Dente, Lajeadinho and Monte-Olimpo; slightly or not deficient: Iracema soil series. The sunflower bioassay indicated that it can be used as an efficient procedure to estimate the level of available soil boron.