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

Tannery industry produces high amounts of nutrient rich sludges that can be used as organic fertilizers.

The aim of this study was to evaluate the fertilizing potential of composted tannery sludge.

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 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.

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.