Arne Sæbø
Research Professor (OAP Agreement)
(+47) 404 74 349
arne.sabo@nibio.no
Place
Særheim
Visiting address
Postvegen 213, NO-4353 Klepp stasjon
Authors
C. Chiodi G. Zardinoni P. Stevanato L. Giagnoni P. Carletti N. Oustrière Arne Sæbø Tomas Persson W. Szulc B. Rutkowska M. Mench G. RenellaAbstract
Abstract Background Soil contamination with metal(loid)s and organic pollutants creates environmental and health concerns, driving the need for sustainable remediation strategies. Organic amendments can mitigate contamination effects, enhancing soil quality, and potentially increasing biomass production; however, their long-term influence remains an open question. In a five-year field experiment at a former wood-preservation site, this study evaluates the effects of five organic amendments—fresh pig manure (PM), biodigested pig manure (PD), compost (C), compost pellets (Pt), and green waste compost (G)—on Cu-contaminated soils. Here, we evaluated their impacts on physico-chemical soil properties, metal bioavailability, microbial community structure, plant growth and soil fertility. Results All amendments led to an overall soil improvement, including enhanced physico-chemical properties, increased enzyme activities. The amendments promoted the concentration of soil 16S bacterial genes and improved the yield of winter barley cultivated in the plots. The most abundant phyla detected across soil samples were Actinobacteriota , Proteobacteria , and Firmicutes , with Bacillus , Streptomyces , and Bradyrhizobium among the dominant genera. Compost-based amendments at 5% w/w addition rate (C5 and Pt5) showed the most promising results, significantly increasing soil carbon, nitrogen, and phosphorus contents, while reducing bioavailability of Cd, Ni, Pb, and Zn compared with untreated control plots ( p < 0.01). A decrease in Cu availability was observed but it was not significant. The Pt5 soils exhibited the highest 16S rRNA gene copy number ( p < 0.01). Both compost and compost pellets amendments enriched microbial communities associated with soil quality and plant yield, leading to significant improvements in soil fertility and barley yield (+ 200% on average). Conclusion This integrative approach identified organic amendments, notably compost and pelleted compost, that effectively contribute to soil remediation from multiple perspectives: chemical properties (pH, organic content, nutrients), reduction of bioavailable soil Cd and Zn, enzyme activities, microbial abundance and diversity (16S rRNA), and winter barley yield. The study evidenced signature biomarkers characteristic of healthy soils ( Paenibacillus , Lysinibacillus , and Agromyces ) and polluted soils ( Candidatus Solibacter and Mycobacterium ). Our findings support the use of compost (raw and pelleted) as a balanced approach for phyto-managing metal-contaminated soils, reducing 1 M NH 4 NO 3 -extractable soil Cd and Zn while enhancing microbial activity and soil fertility. Graphical Abstract
Abstract
To facilitate nutrient management and the use of manure as a feedstock for biogas production, manure is often separated into a solid and a liquid fraction. The former fraction is usually high in P and low in N, so when incorporated in the soil as fertilizer, it needs to be supplemented by N from, e.g., mineral fertilizers or nitrogen-fixing species. To explore strategies to manage N with solid-separated manure, we examined how the amount of digestate and the N:P ratio of pig digestate, i.e., manure that had partially undergone anaerobic digestion, affected the productivity of Westerwolds ryegrass and red clover in a pot experiment with one soil which was rich and another which was poor in plant nutrients. The soil and plant species treatments were combined with four doses of digestate, which gave plant available phosphorus (P) concentrations of 2, 4, 8, or 16 mg P100 g−1 soil. Ammonium nitrate was dosed to obtain factorial combinations of digestate amount and N:P ratios of 1.8, 4, 8, and 16. Clover was harvested once at the beginning of flowering (15 weeks after seeding), while Westerwolds ryegrass was allowed to regrow three times after being cut at the shooting stage (in total, 4 cuts, 6, 9, 12, and 15 weeks after seeding). Ryegrass yield increased by up to 2.9 times with digestate dosage. Interactions with the N:P ratio and soil type were weak. Hence, the effect of increasing the N:P ratio was additive across digestate dosages. Red clover biomass also increased by up to 39% with digestate dosage. Residual nutrients in the soil after red clover cultivation were affected by the initial differences in soil characteristics but not by digestate treatment or biomass of harvested red clover. A targeted N management is required to benefit from the P-rich digestate in grass cultivation, while the long-term effects of red clover culture on N input need further investigation.
Abstract
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