On air

Agriculture can affect air quality through emission of various gases, two of which ammonia and nitrous oxide are associated with crop nutrients. Ammonia contributes to acid rain and to nitrogen additions to sensitive natural ecosystems. Most of the ammonia produced by agriculture is associated with animal manures but a small amount is lost following application of some nitrogen fertilizers, particularly urea.

The role of mineral fertilizer.

Losses from fertilizers can be minimised if excessive applications are avoided and Yara has developed a range of advisory services to help farmers achieve best practise. In wet soils, where oxygen concentration is low, certain bacteria can convert nitrate into gaseous nitrous oxide and di-nitrogen which are lost to the air. Di-nitrogen is harmless but nitrous oxide acts as a greenhouse gas and may damage stratospheric ozone. Most of the agricultural nitrous oxide derives from the application of livestock manures but a small proportion can be attributed to fertilizer nitrogen use. Under certain conditions, high levels of nitrate in the soil promote nitrous oxide formation so measures that minimise soil nitrate by matching nitrogen supply to crop need also help minimise nitrous oxide loss.

 Yara has conducted two major reviews of world scientific literature on ammonia and nitrous oxide losses to air, to develop a strong knowledge base. Both have been published in the Norwegian Journal of Agricultural Sciences.

In response to this knowledge, we have developed nitrogen advisory systems and technologies to contribute to minimising nitrogen losses of both ammonia and nitrous oxide from the soil.

Granli T and Bockman O C (1994) Nitrous oxide from agriculture. Norwegian Journal of Agricultural Sciences, Supplement No. 12. (128 page review of the scientific literature available in English)

Holtan-Hartwig L and Bockman O C (1994) Ammonia exchange between crops and air. Norwegian Journal of Agricultural Sciences, Supplement No. 14. (41 page review of the scientific literature available in English)