Effect of sewage sludge-derived amendments on the nutrient uptake by Chinese cabbage from Mediterranean soils

Abstract

The utilization of sewage sludge (SS) as a fertilizer for agricultural land is increasingly seen by many as the best option for recycling. This study investigates the effects of SS-derived compost (SSC) or biochar (SSB) amendments on N, P, K, Ca, Mg, Na, Fe, Mn and Mo uptake by Chinese cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt) from terra rossa and rendzina soils. A two-factorial experiment was performed under greenhouse conditions whereby elemental concentrations (substrate, leachates and plants), edible tissue uptake (ETU), concentration ratios (CR) and soil characteristics were determined. The pH (7.03 to 7.32) and P content (286 to 421 mg/kg d.w.) in SSC- and SSB-amended soils increased, while EC (450 to 253 μS/cm) decreased. Phosphorous levels were higher in SSB-amended soils, although P leaching indicates a low environmental risk in both soils. In leaves, P (1.02 to 4.15 g/kg d.w.), K (12.8 to 21.8 g/kg d.w.), Mg (1.05 to 1.55 g/kg d.w.), Na (660 to 1350 mg/kg d.w.), and Mo (1.20 to 2.65 mg/kg d.w.) levels increased with amendment rate and were higher in SSC-amended soils. Nutrient bioavailability also increased with amendment rate, while cabbage biomass production increased proportionally to the dose. The P, K, and Mg levels were higher in leaves, while roots contained more Ca, Fe, and Mn. Despite amendment rates 10x the permitted dose of SS, they did not affect soil leachate, plant growth and biomass yield. Overall, adopting the cautionary principle is advised until the long-term effects are better understood.

Keywords:

• Composting
• Brassica plants
• elemental phytoaccumulation
• pyrolysis
• organic waste recycling
• soil amendment

Acknowledgments

The authors would like to thank the staff of the local municipal company (Usluga Poreč d.o.o. za komunalne poslove) for their cooperation and assistance.

Disclosure statement

No conflict of interest was reported by the authors.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Authors’ contribution statements

Conceptualization and Experimental design: Marko Černe, Igor Palčić, Igor Pasković, Smiljana Goreta Ban, Dean Ban; Sampling and Sample preparation: Marko Černe, Igor Palčić, Zoran Užila, Josipa Perković; Statistical analysis: Marko Černe, Nikola Major, Igor Pasković; Leaching experiment: Marko Černe, Vilim Filipović; Writing-Original draft preparation: Marko Černe, Smiljana Goreta Ban; Writing-Reviewing and Editing: David John Heath, Dean Ban; Trace element analyses: Marija Romić; Soil characteristics determination: Marko Černe, Zoran Užila. All authors have read and agreed to the published version of the manuscript.

Additional information

Funding

The Croatian Science Foundation, the HRZZ Program for encouraging research and development activities in climate change and The Environmental Protection and Energy Efficiency Fund, Croatia, are acknowledged for full financial support of the study (contract No. PKP-2016-06-9041).