Effects of 15 years sludge application on cropland

Abstract

Sewage sludge effects to cropland have been evaluated in a long-term field experiment which started in 1988 and is still underway in the eastern part of the Po Valley (Italy), on a silty-loam soil. Each autumn municipal-industrial wastewater sludge has been applied at 5 and 10 Mg DM ha-1 yr-1 as anaerobically digested slurry (liquid), belt filtered material (dewatered) and composted with wheat straw, on a winter wheat - maize - sugar beet rotation. The 15 years continuous application of sludge significantly increased organic matter, total N, Olsen P, Cu and Zn content in the topsoil, with greater effects at the highest rate. Composted sludge favoured the highest OM topsoil increase. Sludge spreading improved soil fertility and crop yields, but it was associated with possible negative environmental effects: on water, due to increased phosphorus availability, and on soil ecology, due to zinc build up in the topsoil. The results confirmed that compulsory application rates based on real crop nitrogen requirements and matching Nitrate EU Directive, undoubtedly can guarantee a sound sustainability in sewage sludge recycling on cropland in the long run.

Greenhouse gas emissions of electricity and biomethane produced using the Biogasdoneright™ system: four case studies from Italy

“…A mass balance approach is used to quantify the SOC change by applying digestate and organic matter of crop residues from double crops. About 12% of organic matter (OM) from digestate and crop residues is converted to SOC . Thus, the annual increase of SOC is 0.2–0.3 t C per ha.…”

“…About 12% of organic matter (OM) from digestate and crop residues is converted to SOC. 17,18 Th us, the annual increase of SOC is 0.2-0.3 t C per ha. Th ese values are close to those obtained from fi eld trials using conservation agriculture practices.…”

The Foreground Analysis of Sewage Sludge Agriculture Application in China

“…The heavy metal in sewage sludge is an important limitative factor of sludge agricultural land. Mantovi P, et al [11] pointed to that 15 years of repeated sludge land spreading improved soil fertility by increasing organic matter and nutrients, but caused build up of some heavy metal (Cu and Zn), and polluted surface water due to an increasing phosphorus availability, and soil ecology was damaged due to Zinc accumulation in soil. Many chemical matter and heavy metal in sewage sludge easily cumulated in fatty tissue and butterfat [12].…”