Effectiveness of Five Biosolids as Nitrogen Sources to Produce Single and Cumulative Ryegrass Harvests in Two Australian Soils

Douglas José Da Silva,Rodrigo Studart Corrêa

doi:10.1590/18069657rbcs20150216

Douglas José Da Silva, Rodrigo Studart Corrêa

Open Access

https://doi.org/10.1590/18069657rbcs20150216

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Abstract

Biosolids have been produced by various stabilization processes of sewage sludge, but little attention has been given to the effects of such treatments on their effectiveness to supply nitrogen for plant growth. Here, we investigated these effects by cultivating Lolium perenne (ryegrass) in two Australian soils, a sandy Spodosol and a clayey Oxisol. Biosolids stabilized by either aerobic digestion, composting, CaO-liming, 250 oC heat-drying or solar irradiation of domestic sewage sludge were applied to soils at 10 increasing rates (0.25-8.0 dry Mg ha-1), and chemically fertilized soils were used as reference. Results showed that the stabilization processes affected biosolids-N agronomic rates and effectiveness to yield plant biomass, which was a function of organic-N contents mineralized in soils. In the short term, biosolids were from 1/5 (digested biosolids in Oxisol) to over twice (solar-irradiated biosolids in Spodosol) as effective as chemical fertilizer to produce a first single harvest. As long-term N-sources, they significantly increased the effectiveness to produce plant biomass, being from 2.0 to 4.1 times more effective than chemical fertilizer in Spodosol and 1.5-2.4 times in Oxisol. Biosolids could substitute for N fertilizer with similar or higher effectiveness to yield plant biomass, depending on the sewage sludge stabilization process, soil type and cultivation term considered. Therefore, the sound management of sewage products as N sources for crop production should consider the interaction among these factors rather than solely their N content.

Highlights

Sewage sludge contains significant concentrations of organic matter, nitrogen, phosphorus and other elements that improve soil structure and fertility, stimulate microbial activity, enhance root penetration and increase crop yield (Al-Dhumri et al, 2013; Jorge-Mardomingo et al, 2013; Jeke et al, 2015)
Biosolids stabilized by either aerobic digestion, composting, CaO-liming, 250 oC heat-drying or solar irradiation of domestic sewage sludge were applied to soils at 10 increasing rates (0.25-8.0 dry Mg ha-1), and chemically fertilized soils were used as reference
Results showed that the stabilization processes affected biosolids-N agronomic rates and effectiveness to yield plant biomass, which was a function of organic-N contents mineralized in soils

Summary

Introduction

Sewage sludge contains significant concentrations of organic matter, nitrogen, phosphorus and other elements that improve soil structure and fertility, stimulate microbial activity, enhance root penetration and increase crop yield (Al-Dhumri et al, 2013; Jorge-Mardomingo et al, 2013; Jeke et al, 2015). Prices of chemical fertilizers and favorable costs of sludge land application compared to other disposal options have been decisive for recycling sewage sludge components in soils (Winker et al, 2009). Concentrations of metals, organic contaminants, N and P are often the controlling design parameters for long-term land application of biosolids, while pathogens, odors and vector attraction may prevent a site or a crop from receiving a single application of sewage products (Winker et al, 2009). Sludge digestion, composting, lime stabilization, heat treatment and solar irradiation are commonly employed for turning putrescible sewage materials into stable biosolids (USEPA, 1995; EPA, 2004; Conama, 2006)

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