Eftervirkning af kvælstof i N-fikserende efterafgrøder, nitratudvaskning og kulstofbinding

Nyeste viden om faktorer, der har betydning for størrelsen af eftervirkning, samt faktorer, der kan påvirke nitratudvaskningen og kulstofbinding

Nitrogen leaching: a crop rotation perspective on the effect of N surplus, field management and use of catch crops

Components of the field nitrogen (N) balance (input and surplus) are often used to predict nitrate leaching from agricultural lands. However, management factors, such as use of catch crops, greatly affect the actual loss and are a key to reduce N leaching. The present study is based on the 4th cycle of a long-term crop rotation experiment in Denmark, and it aims to quantify, from a crop rotation perspective, the influence on N leaching from N input and surplus or management factors. The experiment included three cropping systems (two organic and one conventional) with or without use of animal manure and catch crops. N leaching was calculated from measurements of nitrate in soil water sampled with ceramic suction cups installed at 1 m depth in all plots. At the rotation level, over a four years period, N leaching was positively related to N input and surplus. However, the overall effect of N input and surplus on N leaching was lower than the effect of use of catch crops. The response rates of N leaching to increasing N inputs and N surplus were about 0.08 and 0.19-0.25, respectively. Catch crops reduced N leaching by 23 kg N ha-1, irrespective of conventional and organic management system, with legume-based catch crops being as effective as non-legumes. Animal manure increased N leaching in one of the organic systems. The organic system with two years of green manure per rotation cycle was the one at highest risk of N leaching, especially from crops following green manure incorporation. Spring wheat and potatoes were the two crops with highest N leaching, and a stable low level of N leaching was only achieved above a crop-specific threshold in catch crop biomass

Row spacing and catch crop establishment in organic arable systems: a way to increase biological N fixation

Increasing the row space of spring wheat from 12 to 24 cm, but maintaining the same seeding density, didn´t decrease its yield. On the other hand, it positively influenced the growth of the undersown catch crop, a mixture of red clover, white clover, rye grass and chicory

Flerårigt sædskifte med tætning som alternativ til pligtige efterafgrøder

Dette er en rapport om anvendelsen af N-fikserende efterafgrøder som pligtige efterafgrøder, skrevet på foranledning af en bestilling fra Landbrugsstyrelsen. Det vurderes, at der gennemsnitligt set ikke er risiko for øget kvælstofudvaskning (på kort og længere sigt) ved anvendelse kvælstoffikserende efterafgrøder i artsblanding med ikke-fikserende arter i forhold til anvendelse af ikke-fikserende efterafgrøder. Dette er under forudsætning af, at der indregnes en gødningsmæssig eftervirkning på ca. 50 kg N/ha både på bedrifter under og over 80 kg N/ha i husdyrgødning

Challenges of accounting nitrous oxide emissions from agricultural crop residues

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

Challenges of accounting nitrous oxide emissions from agricultural crop residues

Crop residues are important inputs of carbon (C) and nitrogen (N) to soils and thus directly and indirectly affect nitrous oxide (N$_2$O) emissions. As the current inventory methodology considers N inputs by crop residues as the sole determining factor for N$_2$O 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 N$_2$O 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 N$_2$O 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 N$_2$O 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 N$_2$O 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 N$_2$O emissions

Challenges of accounting nitrous oxide emissions from agricultural crop residues

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

Agroecological practices for climate change mitigation

Agroecology can be defined as an integrated approach to agriculture and food systems, combining ecological and social principles to agricultural management and food systems design. Thanks to its holistic approach towards sustainability, agroecology can help tackle climate change challenges, from both mitigation and adaptation perspectives. Agroecological practices such as the use of cover crops and green manures have the potential to increase carbon stored in the soil, as well as soil fertility, mitigating climate change and at the same time improving crop productivity. Nonetheless, it has been shown that practices that can have a positive effect on carbon sequestration might increase emissions of other greenhouse gasses, such as nitrous oxide. This webinar will provide an overview on agroecological practices and climate change, and present results from field experiments on the effect of cover crops on carbon and nitrogen in the soil, with related implications for climate change mitigation