Bentonite as substrate conditioner under different water regimes – A Eucalyptus dunnii seedling assay

The substrate has a lot of functions in the process to develop a high-quality seedling, including the responsibility to hold water and to make the water available for the plants. A compound that can be used to hold water is bentonite. So, the research aimed to evaluate the effects of different proportions of bentonite as a substrate component under two water conditions in the production of Eucalyptus dunniii seedlings. The research was carried out in the forest seedlings nursery in Curitiba/PR - Brazil. For the treatments, bentonite substrate conditioner was used in different proportions, 0 %, 5 %, 10 %, 15 % and 20 %, in a commercial substrate (with sphagnum peat) here named as S0, S5, S10, S15 and S20 respectively, in two water regimes for the blocks. The seedlings produced with these bentonite proportions was analyzed by the height, stem diameter, dry matter (shoot, root and total), and two parameters: height/stem diameter ratio (H/SD) and Dickson Quality Index (DQI). The substrate analysis shown a contrary behavior of expected. The bentonite in the substrate for seedlings of E. dunnii did not increase water holding capacity in a linear form and the high proportion of bentonite did not improve seedling in the lower water regime, although the 5 % of bentonite gave a good results of seedlings growth, so the purpose of bentonite in the substrate to improve water holder capacity and minimize the irrigation would not be fully attended.