title: Plant growth improvement mediated by nitrate capture in co-composted biochar.
abstract: Soil amendment with pyrogenic carbon (biochar) is discussed as strategy to improve soil fertility to enable economic plus environmental benefits. In temperate soils, however, the use of pure biochar mostly has moderately-negative to -positive yield effects. Here we demonstrate that co-composting considerably promoted biochars' positive effects, largely by nitrate (nutrient) capture and delivery. In a full-factorial growth study with Chenopodium quinoa, biomass yield increased up to 305% in a sandy-poor soil amended with 2% (w/w) co-composted biochar (BC(comp)). Conversely, addition of 2% (w/w) untreated biochar (BC(pure)) decreased the biomass to 60% of the control. Growth-promoting (BC(comp)) as well as growth-reducing (BC(pure)) effects were more pronounced at lower nutrient-supply levels. Electro-ultra filtration and sequential biochar-particle washing revealed that co-composted biochar was nutrient-enriched, particularly with the anions nitrate and phosphate. The captured nitrate in BC(comp) was (1) only partly detectable with standard methods, (2) largely protected against leaching, (3) partly plant-available, and (4) did not stimulate N2O emissions. We hypothesize that surface ageing plus non-conventional ion-water bonding in micro- and nano-pores promoted nitrate capture in biochar particles. Amending (N-rich) bio-waste with biochar may enhance its agronomic value and reduce nutrient losses from bio-wastes and agricultural soils.
authors.affiliation: Department of Plant Ecology, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
authors.forename: Claudia I
authors.initials: CI
authors.lastname: Kammann
authors.affiliation: Ithaka Institute for Carbon Intelligence, Ancienne Eglise 9, CH-1974 Arbaz, Switzerland.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Schmidt
authors.affiliation: Department of Plant Ecology, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Messerschmidt
authors.affiliation: Department of Plant Ecology, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Linsel
authors.affiliation: Institute of Plant Nutrition, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
authors.forename: Diedrich
authors.initials: D
authors.lastname: Steffens
authors.affiliation: 1] Department of Plant Ecology, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany [2] Earth Science Institute, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Müller
authors.affiliation: Department of Plant Ecology, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
authors.forename: Hans-Werner
authors.initials: HW
authors.lastname: Koyro
authors.affiliation: Dipartimento di Scienze Agrarie e Forestali, Università degli Studi di Palermo, viale delle Scienze ed. 4 90128 - Palermo (Italy).
authors.forename: Pellegrino
authors.initials: P
authors.lastname: Conte
authors.affiliation: Discipline of Chemistry, University of Newcastle, Callaghan, NSW 2308, Australia; University of New South Wales, School of Material Science and Engineering, NSW 2052, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Joseph
authors.forename: Joseph
authors.initials: J
authors.lastname: Stephen
mesh_terms: D018533:Biomass; D002606:Charcoal; D027462:Chenopodium / Q000254:growth & development*; D009566:Nitrates / Q000378:metabolism*
chemical_list: D009566:Nitrates; C540010:biochar; D002606:Charcoal