Sewage Sludge Compared with Other Substrates in the Inoculation, Growth, and Tolerance to Water Stress of Samanea saman

Abstract

This study evaluated the initial growth and tolerance to water stress after planting Samanea saman seedlings produced with different substrates and inoculation patterns. The experiment used a factorial design (3 × 3), with three substrates: standard (67% subsoil + 33% cattle manure), a commercial substrate (composed mainly of peat), and treated sewage sludge; and three inoculation patterns: control (no inoculation), fertilized (no inoculation + chemical fertilization), and inoculation with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi. The seedlings were planted in plastic pots inside a greenhouse. They received irrigation after planting and were submitted to water deficit for 35 days, followed by rehydration for 31 days. The inoculation promoted higher height and biomass for seedlings produced in the standard substrate. In the sludge, the roots biomass decreased when fertilized or inoculated. Seedlings grown in sludge showed higher height and biomass before planting and at the end of the experiment. Although, after rehydration, the height increment was similar for the sludge and the standard substrate. Seedlings grown with the commercial substrate are not recommended for planting sites subjected to water deficit. The standard substrate with inoculation and the sludge without inoculation or fertilization produced seedlings that showed better recovery and growth after water deficit.