Ishita Ahuja
Post Doctor
(+47) 458 37 316
ishita.ahuja@nibio.no
Place
Steinkjer
Visiting address
Innocamp Steinkjer, Skolegata 22, 7713 Steinkjer
Authors
Jørgen E. Olesen Robert M. Rees Sylvie Recous Marina Azzaroli Bleken Diego Abalos Ishita Ahuja Klaus Butterbach-Bahl Marco Carozzi Chiara De Notaris Maria Ernfors Edwin Haas Sissel Hansen Baldur Janz Gwenaëlle Lashermes Raia S. Massad Søren O. Petersen Tatiana Francischinelli Rittl Clemens Scheer Kate E. Smith Pascal Thiébeau Arezoo Taghizadeh-Toosi Rachel E. Thorman Cairistiona F. E. ToppAbstract
Crop residues are important inputs of carbon (C) and nitrogen (N) to soils and thus directly and indirectly affect nitrous oxide (N2O) emissions. As the current inventory methodology considers N inputs by crop residues as the sole determining factor for N2O emissions, it fails to consider other underlying factors and processes. There is compelling evidence that emissions vary greatly between residues with different biochemical and physical characteristics, with the concentrations of mineralizable N and decomposable C in the residue biomass both enhancing the soil N2O production potential. High concentrations of these components are associated with immature residues (e.g., cover crops, grass, legumes, and vegetables) as opposed to mature residues (e.g., straw). A more accurate estimation of the short-term (months) effects of the crop residues on N2O could involve distinguishing mature and immature crop residues with distinctly different emission factors. The medium-term (years) and long-term (decades) effects relate to the effects of residue management on soil N fertility and soil physical and chemical properties, considering that these are affected by local climatic and soil conditions as well as land use and management. More targeted mitigation efforts for N2O emissions, after addition of crop residues to the soil, are urgently needed and require an improved methodology for emission accounting. This work needs to be underpinned by research to (1) develop and validate N2O emission factors for mature and immature crop residues, (2) assess emissions from belowground residues of terminated crops, (3) improve activity data on management of different residue types, in particular immature residues, and (4) evaluate long-term effects of residue addition on N2O emissions.
Authors
Ishita Ahuja Inger Sundheim Fløistad Per Grande Øyvind Meland Edvardsen Adam O’Toole Arne SteffenremAbstract
No abstract has been registered
Abstract
Fishbones contain significant amounts of plant nutrients. Fish residues may be preserved by acidification to pH < 4, which may affect the chemical extractability, and the plant availability of nutrients when applied as fertilisers. Grinded bone material from cod (Gadus morhua) heads was mixed with formic acid to investigate if this would increase the concentrations of ammonium lactate–acetate (AL)-extractable nutrients. Two degrees of fineness of fishbones (coarse 2–4 mm; fine < 0.71 mm) were compared at pH 3.0 and 4.0 plus a water control in a laboratory study over 55 days. Samples for measurement of AL-extractable P, Ca, Mg and K were taken on day 2, 15, 34 and 55. Whereas more formic acid and thereby lower pH clearly increased the concentrations of AL-extractable calcium (Ca-AL) and magnesium (Mg-AL), AL-extractable phosphorus (P-AL) was only significantly increased in finely grinded bones at pH 3. After 34 days at pH 3, 6% of the total content of P was extracted by AL in fine fishbones. In the water control, about 1% of the P was extracted, possibly from phospholipids. This P-AL concentration was well above P-AL extracted from acidified coarse fishbones (pH 3 and 4) and from fine fishbones acidified to pH 4. With acidification, about 30% of total Ca and 100% of total Mg were extracted by AL, and the Ca-AL and Mg-AL concentrations were closely correlated. A possible reason for lower P-AL in coarse fishbones at pH 3 and 4, and in fine fishbones at pH 4 than in water controls may be a precipitation of apatite from phospholipids and dissolved calcium.
Abstract
No abstract has been registered
Authors
Diego Abalos Tatiana Francischinelli Rittl Sylvie Recous Pascal Thiébeau Cairistiona F. E. Topp Kees Jan van Groenigen Klaus Butterbach-Bahl Rachel E. Thorman Kate E. Smith Ishita Ahuja Jørgen E. Olesen Marina Azzaroli Bleken Robert M. Rees Sissel HansenAbstract
Crop residue incorporation is a common practice to increase or restore organic matter stocks in agricultural soils. However, this practice often increases emissions of the powerful greenhouse gas nitrous oxide (N2O). Previous meta-analyses have linked various biochemical properties of crop residues to N2O emissions, but the relationships between these properties have been overlooked, hampering our ability to predict N2O emissions from specific residues. Here we combine comprehensive databases for N2O emissions from crop residues and crop residue biochemical characteristics with a random-meta-forest approach, to develop a predictive framework of crop residue effects on N2O emissions. On average, crop residue incorporation increased soil N2O emissions by 43% compared to residue removal, however crop residues led to both increases and reductions in N2O emissions. Crop residue effects on N2O emissions were best predicted by easily degradable fractions (i.e. water soluble carbon, soluble Van Soest fraction (NDS)), structural fractions and N returned with crop residues. The relationship between these biochemical properties and N2O emissions differed widely in terms of form and direction. However, due to the strong correlations among these properties, we were able to develop a simplified classification for crop residues based on the stage of physiological maturity of the plant at which the residue was generated. This maturity criteria provided the most robust and yet simple approach to categorize crop residues according to their potential to regulate N2O emissions. Immature residues (high water soluble carbon, soluble NDS and total N concentration, low relative cellulose, hemicellulose, lignin fractions, and low C:N ratio) strongly stimulated N2O emissions, whereas mature residues with opposite characteristics had marginal effects on N2O. The most important crop types belonging to the immature residue group – cover crops, grasslands and vegetables – are important for the delivery of multiple ecosystem services. Thus, these residues should be managed properly to avoid their potentially high N2O emissions.
Authors
Ishita AhujaAbstract
No abstract has been registered
Authors
Ishita AhujaAbstract
No abstract has been registered
Authors
Maria Bjørkman Ishita Ahuja Annette Folkedal Schjøll Nicole Van Dam Atle M. Bones Richard MeadowAbstract
No abstract has been registered
Authors
Ishita Ahuja Maria Björkman Annette Folkedal Schjøll Aysel Heydarova Ralph Kissen Nicole Van Dam Richard Meadow Atle M. BonesAbstract
No abstract has been registered
Authors
Ishita Ahuja Nicole Van Dam Maria Björkman Eleanna Kazana Glen Powell Annette Folkedal Schjøll Ralph Kissen Aysel Heydarova Jens Rohloff Richard Meadow John Trevor Rossiter Atle M. BonesAbstract
No abstract has been registered
Authors
Maria Björkman Ishita Ahuja Annette Folkedal Schjøll Nicole van Dam Atle M. Bones Richard MeadowAbstract
No abstract has been registered
Authors
Maria Björkman Ishita Ahuja Annette Folkedal Schjøll Nicole Van Dam Atle M. Bones Richard MeadowAbstract
No abstract has been registered
Authors
Birgit Hafeld Borgen Ishita Ahuja Ole Petter Thangstad Bjørn Ivar Honne Jens Rohloff John Trevor Rossiter Atle M. BonesAbstract
No abstract has been registered
Authors
Ishita Ahuja Birgit Hafeld Borgen Magnor Kåre Hansen Bjørn Ivar Honne Caroline Müller Jens Rohloff John Trevor Rossiter Atle M. BonesAbstract
No abstract has been registered