Use of urban sewage sludge as a substrate for the production of Australian red cedar (Toona ciliata) and Brazilian pepper (Schinus terebinthifolius) seedlings

Abstract

The sewage sludge, according to the hygiene process to which it is submitted, has potential for use in agriculture, given the supply of organic matter and nutrients to vegetables. The objective of this study was to evaluate the use of urban sewage sludge, as a substrate component for the production of Australian red cedar and Brazilian pepper seedlings, after an alkaline stabilization treatment. The sewage sludge - associated with vermiculite or commercial substrate - composed the substrates in different proportions (0, 25, 50, 75 e 100%). After harvest, seedling development parameters and nutrient contents were analyzed. The addition of sewage sludge reduced the development of the Australian red cedar seedlings, probably due to its high pH after alkaline stabilization, which reduced the concentrations of potassium and, mainly, phosphorus available in the substrate. For Brazilian pepper seedlings, it is observed that the addition of sewage sludge up to the proportion of 50%, favored the development of the seedlings, thus demonstrating a lower demand for Brazilian pepper to the presence of exchangeable P. Partial budgeting has shown that for the cultivation of Australian red cedar seedlings it is not recommended to replace the commercial substrate with any studied combination containing sewage sludge. In the cultivation of Brazilian pepper seedlings, the use of 25% or 50% of sewage sludge is recommended, with the best financial result for the treatment containing 25% sewage sludge and 75 % commercial substrate.