Effect of Different Tannery Sludge Composts on the Production of Ryegrass: A Pot Experiment

Abstract

Background: Tannery industry produces high amounts of nutrient rich sludges that can be used as organic fertilizers. Objective: The aim of this study was to evaluate the fertilizing potential of composted tannery sludge. Methods: A pot experiment was carried out with ryegrass (Lolium perenne L.) to test two different composts: 2.0 kg dry matter (DM) tannery fatty sludge + 1.5 kg DM sheep manure + 1.5 kg DM wheat straw (Compost 1) and 2.0 kg DM tannery sludge + 1.5 kg DM sheep manure + 1.5 kg DM wheat straw (Compost 2). Five treatments, with three replicates each, were assigned: Control (C); Compost 1 at 6 t (C1-6) and 12 t (C1-12) DM ha-1; Compost 2 at 6 t (C2-6) and 12 t (C2-12) DM ha-1. Each treatment was applied in a pot and mixed with 5 kg of sieved soil (<2 mm). Results: Results showed that production of DM ranged between 1.2 t DM ha-1 for C1-6 and 2.4 t DM ha-1 for C2-12. The highest B, Na and N levels in ryegrass was observed in C2-12, with 175 mg kg-1 DM, 9 g kg-1 DM and 30 g kg-1 DM, respectively. At the end of the experiment no differences were observed between treatments for C, N, P2O5, and K2O levels. Differences were observed at Zn level ranged between 101 mg kg-1 DM for C1-6 and 71 mg kg-1 DM for C2-12. Conclusion: The C2-12 treatment was the best because induces higher DM production and nutrients in ryegrass and without dangerous concentration of heavy metals in soil. Composted waste from the tannery industry is a good source of nutrients for agriculture.