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A barley that is particularly good at taking up nitrogen from the soil would not only reduce nitrogen leaching, it would also reduce the contribution to global warming. This is shown in a life cycle analysis performed by researchers at Mistra Biotech.
One could say that this analysis is a prediction about how crops with efficient nitrogen uptake would affect crop production in general.
A barley variety that takes up more nitrogen compared to the varieties of today would be more climate friendly thanks to (1) a higher yield, (2) an increased storage of carbon in the plants due to more biomass, and (3) a reduced emission of of the greenhouse gas nitrous oxide.
To be able to grow crops more effectively and get higher yields, with lower or sustained inputs, goes hand in hand with lower emissions from agriculture.
– A nitrogen efficient crop cannot save the Baltic Sea by itself, but it can be an important tool in combination with other actions that are used, or discussed, says Pernilla Tidåker, one of the researchers behind the study.
How can barley, wheat, rice and other crops be tailored to take up nitrogen more efficiently? One strategy is to develop varieties with a denser and deeper root system. Another strategy is to use biotechnology to alter the activity of the enzymes that affect the uptake of nitrogen in plants.
Today there are no commercial varieties available that have been made nitrogen efficient though biotechnology, but research and pre-breeding is underway. In Mistra Biotech we develop potato varieties with increased nitrogen uptake.
In the absence of commercial nitrogen efficient crops and long-term field trials, the researchers have instead used three simulation models (SOILN, SOILNDB and ICBM) to estimate the effects of an introduction of barley varieties with improved nitrogen uptake. They investigated the effects on yield, nitrogen leaching and carbon storage. The simulations were based on conditions typical for barley cultivation in the south of Sweden and areas close to the lakes Hjälmaren and Mälaren.
– A nitrogen efficient crop would have most effect in the south through reduced nitrogen leaching. Our study indicates that the increased biomass, and thereby the carbon storage, has a large impact on whether a crop is climate friendly or not. When evaluating the environmental impact of a crop, we should focus more on what is returned to the soil after we have taken out what we wanted, in this case the grain, and emphasize the total biomass, not only the grain yield, says Pernilla Tidåker.
She also points out the risk that a crop with a higher nitrogen uptake efficiency could result in farmers using more nitrogen fertilizer.
– That does not mean that there will be an increased nitrogen leaching. But if a crop is very efficient in taking up nitrogen initially, it might suffer from nitrogen deficiency later on if more nitrogen is not added. If we should introduce such a crop,we might also need incentives for farmers to keep nitrogen application rates maintained, says Pernilla Tidåker.
More information: Pernilla Tidåker, firstname.lastname@example.org, 010 - 516 69 41
Tidåker, P., Bergkvist, G., Bolinder, M., Eckersten, H., Johnsson, H., Kätterer, T., & Weih, M. 2016. Estimating the environmental footprint of barley with improved nitrogen uptake efficiency - a Swedish scenario study. European Journal of Agronomy 80: 45-54
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