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FFL-JA-Forskningsmidlene for jordbruk og matindustri

Assessment of cover cropping as climate action in cereal production in Norway

Alternative title: Fangvekster som klimatiltak i norsk kornproduksjon

Awarded: NOK 7.2 mill.

Cover crops are grown to keep the soil covered with plants after harvest of the main crop. In Norway, cover crops were introduced in the 1990's to prevent loss of nitrogen and phosphorous from fields to waterways. Cover crops contribute with several ecosystem services and are considered an applicable climate action. However, it can currently not be posted in the greenhouse gas accounts for the agricultural sector in Norway because of insufficient documentation of its effect under our conditions. The aim of CAPTURE is to document the climate effect of using cover crops in cereal production in Norway, as well as to develop well-functioning cultivation strategies. The climate effect in this context is the ability cover crops have to sequester carbon weighed against both nitrate leaching and nitrous oxide emissions from decomposing plant residues in the soil. In a field trial, selected cover crop species are marked with the carbon isotope C13 to follow the flow of carbon to soil and its distribution in organic matter fractions. Together with data on biomass production under real farming conditions, this will provide input to a model for predicting long-term trends of carbon sequestration in accordance with the UN Climate Panel's methodology. The ability of different cover crop species to preserve nitrogen and avoid risk of direct and indirect nitrous oxide emissions during different seasons will be documented in field trials. Fertilization of cover crops is included as a treatment in the experiment. An on-farm survey will provide data from two growing seasons on cultivation practices and the amount and variation in biomass of cover crops in Southeast- and Mid Norway. In addition, experiments in the cereal production regions will provide more knowledge about species and cultivation methods that minimize potential trade-offs and optimize the overall effect of cover cropping.

Use of cover crops (CC) in cereal cropping has been proposed as a viable option to reduce greenhouse gas emissions in Norwegian agriculture, based on results of Swedish long-term experiments which showed appreciable net carbon (C) sequestration in soil. Few data from long-term experiments with CCs are available for Norway and sequestration of C cannot very easily be inferred from short term experiments. To parameterize models that can predict C sequestration by use of CCs under Norwegian conditions, an on-farm survey and a series of experiments will be initiated testing different cover crops in Norway’s main cereal regions for their yield potential with and without nitrogen fertilization. Detailed process studies with 13CO2 pulse labelling at one site (Ås) will be used to quantify short-term C sequestration in a SE Norwegian clay loam. The data will be used to parameterize the Introductory Carbon Balance Model (ICBM). The core experiment at Ås will be complemented by detailed nitrous oxide (N2O) emission measurements to quantify the trade-offs between C sequestration and increased N2O emissions, especially during the winter season. The effect of CCs on off-season nitrate leaching will be addressed by collecting leachate in Apelsvoll’s field lysimeter facility. There is little knowledge about how to optimize growth of CCs under Norwegian conditions for soil C capture without compromising grain yields and increasing N2O emissions. CAPTURE will test various management strategies regarding sowing time and fertilization for existing (rye grass) and CCs new to Norwegian cereal production (winter vetch, oilseed radish, phaselia, etc.) with emphasis on regional differences in day length and climatic conditions. The generated data will be used as a framework for model estimates of both C input and nitrogen emissions in different cover cropping systems, that can be used for developing guidelines for farmers and, ultimately, for national emission inventories.

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FFL-JA-Forskningsmidlene for jordbruk og matindustri