Carbon mineralization, biological indicators, and phytotoxicity to assess the impact of urban sewage sludge on two light‐textured soils in a microcosm

Abstract

The agricultural reuse of urban sewage sludge (USS) modifies soil properties depending on sludge quality, management, and pedo‐environmental conditions. The aim of this microcosm study was to assess C mineralization and subsequent changes in soil properties after USS addition to two typical Mediterranean soils: sandy (Soil S) and sandy loam (Soil A) at equivalent field rates of 40 t ha−1 (USS‐40) and 120 t ha−1 (USS‐120). Outcomes proved the biodegradability of USS through immediate CO2 release inside incubation bottles in a dose‐dependent manner. Accordingly, the highest rates of daily C emission were recorded with USS‐120 (3.7 and 3.9 mg kg−1 d−1 for Soils S and A, respectively) after 84 d of incubation at 25 °C. The addition of USS also improved soil fertility by enhancing soil macronutrients, microbial proliferation, and protease activity. Protease showed significant correlation with N, total organic C, and heterotrophic bacteria, reflecting the biostimulation and bioaugmentation effects of sludge. Soil indices like C/N/P stoichiometry and metabolic quotient (qCO2) varied mostly with mineralization rates of C and P in both soils. Despite a significant increase of soil salinity and total heavy metal content (lead, nickel, zinc, and copper) with USS dose, wheat germination was not affected by these changes. Both experimental soils showed intrinsic (Soil A) and incubation‐induced (Soil S) phytotoxicities that were alleviated by USS addition. This was likely due to the enhancement of biodegradation and/or retention of phytotoxicants originating from previous land uses. Urban sewage sludge amendments could have applications in soil remediation by reducing the negative effects of allelopathic and/or anthropogenic phytoinhibitors.

Effects of Sewage Sludge Application on Plant Growth and Soil Characteristics at a Pinus sylvestris var. mongolica Plantation in Horqin Sandy Land

“…Sardans et al [71] pointed out that inputs of C, N, and P are the major processes that decide the stoichiometry of these nutrient elements in various ecosystems. Although SOC, TN, and TP contents were all altered by SS addition in our study, the decrease of C/N and increase of N/P indicated that microorganisms mineralized the organic carbon fractions and left a surplus N and enhanced P mineralization rate after SS was added to the soil [72].…”

Nutrient management: as a panacea to improve the caryopsis quality and yield potential of durum wheat (Triticum turgidum L.) under the changing climatic conditions

“…This can be particularly beneficial in drought conditions, as the soil can hold more moisture, providing a reservoir for plant growth and reducing seasonal water stress. However, the presence of higher organic matter in sewage sludge can stimulate microbial populations, leading to increased microbial respiration and subsequent water consumption ( Hechmi et al., 2020 ). It clearly indicates that if the soil is already experiencing drought conditions, this increased demand for moisture could further stress crops and reduce their growth and yield potential.…”

Influência da textura do solo receptor e das condições climáticas e ambientais na taxa e fração de mineralização da matéria orgânica no solo

“…de matéria orgânica nativa e à maior atividade microbiana no meio. Em outras pesquisas, todavia, não foi identificada influência da textura do solo nas taxas de mineralização obtidas (HECHMI et al, 2020;MALUF et al, 2015).…”

“…A diferença não foi significativa para a dose de 40 t.ha -1 de lodo, foi significativa quando aplicada uma dose de 120 t.ha -1 . Hechmi et al (2020) (1) taxa de mineralização média indicada nos estudos; (2) LAS: lodos aeróbios; (3) LAN: lodos anaeróbios; (4) NT: nitrogênio total. Fonte: Elaboração dos autores, 2022.…”