Applying Sewage Sludge toEucalyptus grandisPlantations: Effects on Biomass Production and Nutrient Cycling through Litterfall

Paulo Henrique Müller Da Silva,Jean Paul Laclau,Fabio Poggiani

doi:10.1155/2011/710614

Abstract

In most Brazilian cities sewage sludge is dumped into sanitary landfills, even though its use in forest plantations as a fertilizer and soil conditioner might be an interesting option. Sewage sludge applications might reduce the amounts of mineral fertilizers needed to sustain the productivity on infertile tropical soils. However, sewage sludge must be applied with care to crops to avoid soil and water pollution. The aim of our study was to assess the effects of dry and wet sewage sludges on the growth and nutrient cycling ofEucalyptus grandisplantations established on the most common soil type for Brazilian eucalypt plantations. Biomass production and nutrient cycling were studied over a 36-month period in a complete randomized block design. Four experimental treatments were compared: wet sewage sludge, dry sludge, mineral fertilizer, and no fertilizer applications. The two types of sludges as well as mineral fertilizer increased significantly the biomass ofEucalyptustrees. Wood biomass productions 36 months after planting were similar in the sewage sludge and mineral fertilization treatments (about 80 tons ha−1) and 86% higher than in the control treatment. Sewage sludge application also affected positively leaf litter production and significantly increased nutrient transfer among the components of the ecosystem.

Highlights

Sewage sludge resulting from the treatment of urban liquid residue, channeled to treatment stations through the sewage system, is a residue rich in organic matter
We studied the impact of the addition of wet (77% water content) and dried (7% water content) sewage sludges on tree growth and nutrient cycling in experimental plantations of Eucalyptus grandis, established on highly weathered soils (Ferrasol) in Brazil
Our experiment suggests that a minimum delay of 1 week should be respected between wet sewage sludge application and planting of eucalypt seedlings to avoid large mortality rates due to the volatilization of NH3

Summary

Introduction

Sewage sludge resulting from the treatment of urban liquid residue, channeled to treatment stations through the sewage system, is a residue rich in organic matter. This sludge corresponds to only 1% of the volume of sewage waste, but the treatment and final disposal represents 20 to 40% of the operational costs of a treatment station [1]. Environmental impacts of sewage sludge applications in forest plantations are usually much lower than in agriculture since doses required to meet tree nutrient requirements are low [4]. Forest plantations are usually located on low fertile sandy soils and a fast development of Eucalyptus roots makes it possible to take up the nutrients released during sludge decomposition [5]

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Conclusion