Nitrogen emissions in dairy pastures peak in the springtime

MTT Agrifood Research (Finland): The nitrogen emissions from boreal dairy pastures vary depending on the time of year and ley rotation. The emissions peak in spring, when the nitrates accumulated in the soil over the previous summer and winter leach with the melting snow.

Research Scientist Kirsi H. Saarijärvi of MTT Agrifood Research Finland charted the nitrogen emissions caused by intensive grazing in her doctoral dissertation. The topic has not been previously investigated to this extent in boreal conditions.

…Saarijärvi found that much more nitrogen is left behind on a pasture than in silage cutting fields, since the nitrogen outputs from the pasture are much lower than from silage cutting fields. Most of the nitrogen leaving the pasture is absorbed in the milk produced by the cows grazing in the pasture. From an ecological perspective, the nitrogen leaching from the soil is the most significant load from dairy pastures.

…Saarijärvi stresses that measurements must be carried out throughout the four-year ley rotation in order to gain a representative view of the nitrogen emissions. The nitrogen pulse is especially strong in springtime following pasture renewal.…She found that the springtime nitrogen load is increased since the microbial activity in the soil is not entirely shut down for the winter but merely slows down. Therefore, nitrous oxide resulting from microbial processes in winter is emitted in large quantities as the soil thaws during the spring.

…The nitrogen emissions from dairy pastures can be reduced by several fairly simple techniques. Saarijärvi notes that emissions can be cut by reducing fertilisation, for example. A white clover mixture, which binds nitrogen directly from the air, can replace fertilisation in good soil conditions….


A painting by Luca Giordano, around 1684-1686