Nutritional evaluation of Guanandi seedlings fertilized with sewage sludge

ABSTRACT The generation of sewage sludge and the concern with their fate has greatly increased. The objective of this study was to assess the effects of using in natura (SS) or composted sewage sludge (SSC) in comparison with mineral fertilizer (MF) application and a control (CT) treatment on the nutritional status of Guanandi (Calophyllum brasiliense Cambess.) seedlings in a typical Red Oxisol in Brazil. The leaf-level nutritional responses of the Guanandi seedlings to these three different fertilizers and the control were evaluated at 90 and 180 days after planting. Nutritional data of leaf variables were compared between the treatments by means of one-way analysis of variance using the F test and a pair-wise comparison of means done by Tukey’s test. The seedlings that received SS or SSC showed deficiencies in Ca, Mg, and Mn, which were confirmed by a visual diagnosis of their leaf symptoms. However, at 180 days after planting there were significant differences (p < 0.05) for K that was greater for MF, SS and SSC than CT, Mg, with SSC larger than SS, and for S that was greater with SS and SSC uses relative to MF. The results highlight the potential for using SS and SSC, after adding KCl and lime, although the Guanandi was highly demanding of Ca, Mg, and Mn. However, they were able to nutritionally supply seedlings, although the short-term cannot be conclusive as regards the exclusive use of them in place of mineral fertilizers.