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Epandage de produits residuaires organiques et fonctionnement biologique des sols: De la quantification des impacts sur les cycles carbone et azote a l’evaluation multicritere de la pratique a l’echelle de la parcelle

Abstract : Application of organic waste products (OWP) in agriculture makes possible the recycling of their organic matter (OM) and the substitution of mineral fertilizers including nitrogen. With OM addition, OWP modify physical, chemical and biological soil properties with consequences on ecosystem services provided by soils such as soil as habitat and support of biodiversity, supporting or provisioning services as defined by the Millennium Ecosystem Assessment (MEA, 2005). Nevertheless, OWP applied on soils can contain contaminants which can accumulate into soils. They can also impact air quality through NH3 volatilization, GHG emissions, or water quality through leaching of nitrate or other contaminants. All these effects depend on OWP characteristics and their management (doses, application frequencies...). The aims of this work were to assessbenefits and risks associated with repeated OWP applications from various origins on soils in comparison to mineral fertilization. Two long-term field experimental sites were used: QualiAgro field site (started in 1998) and Colmar field site (started in 2000) included in SOERE-PRO (network of long-term field experiments on OWP recycling). The OWP used were: sewage sludge (SS), co-compost of sewage sludge and green waste (GWS), compost of biowaste (BIO), farmyard manure (FYM) and compost of farmyard manure (FYMC), and compost of municipal solid waste (MSW). Experimental laboratory experiments under controlled conditions, including soil-OWP mixtures incubations have clarified the short-term effects on microflora and on nitrogen availability. Measurements of potential N2O emissions and NH3 volatilization were also conducted. Measurements on soil sampled in the field experiments were used to determine the effects of repeated OWP applications on C stocks, total microflora and specified microorganisms implied in N cycle, N availability and crop yield. The observed effects depended on OM quality of OWP. Those with more stable OM (GWS, BIO) generated more important C stocks, followed by FYM and FYMC, then MSW compost and SS. Global biological indicators (such as microbial biomass) increased with C contentsin soils. The most biodegradable OWP (SS and MSW) transitorily stimulated soil microorganisms. SS provided the highest mineral substitution with 83% in Colmar. GWS composts due to their high content in mineral N made possible to substitute 58% of mineral N; 36% to 48% of mineral N were substituted with the other OWP in Colmar. This substitution reached 70% in QualiAgro after 8 amendments. The fertilizing value of OWP decreased with NH3 volatilization that reached up to 13% of total N applied with SS. The N2O emission factors depended on C biodegradability of OWP and they were less than 1% of total N applied for all OWP and mineral fertilizer excepted for SS (1.9%). The C footprint in the field (C storage vs GHG emissions) was more favorable for OWP compared to mineral N mainly because of C storage and mineral substitution capacity. The account of GHG emissions during composting had strong impacts on C footprint which remained favorable for OWP (especially BIO and FYM) compared to mineral fertilizer. All results on the QualiAgro site were used to develop 6 soil quality indices (biodiversity, biological activities, physical properties, soil fertility, soil sanitary status total and available) and one on crop productivity through a multi-criteria approach. These indices make possible to compare multiple effects of OWP. The BIO compost was the best OWP among the site studied which promoted the most beneficial results.
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  • HAL Id : tel-02801385, version 1
  • PRODINRA : 356978

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Fiona Obriot. Epandage de produits residuaires organiques et fonctionnement biologique des sols: De la quantification des impacts sur les cycles carbone et azote a l’evaluation multicritere de la pratique a l’echelle de la parcelle. Sciences du Vivant [q-bio]. AgroParisTech, 2016. Français. ⟨tel-02801385⟩

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