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Investigating the effect of pH and fertiliser on Nitrous oxide production from farm soils

5th Oct 2015

So for the last blog of the month looking at Nitrous oxide here is a piece of research conducted by Theo Platts-Dunn at Lancaster University as part of a Masters programme. Some of the data that informed the study is based on Adam's farm, so this is a great opportunity to see some research in action (which also fits nicely into our theme).

Our thanks to Theo for allowing us to publish it here.

What's is all about?

This project aimed to assess the effectiveness of how nitrification inhibitors work, in conjunction with common inorganic fertiliser (Ammonium Nitrate and Urea), to reduce nitrous oxide emissions from soil after fertiliser application. As the well as the effect of inhibitors on N2O production I was also interested in the effect of the pH on N2O as I had found some lack of clarity regarding its influence in prior research. I designed a laboratory experiment to investigate these themes.

What did it find?

The results of the experiment showed that the nitrification inhibitors drastically reduced the N2O production when applied together with fertiliser compared to fertiliser applied which contained no inhibitor (Up to a 90% reduction). With regard to pH, a slightly more acidic soil generally results in lower N2O production. This was true with the ammonium nitrate treated cores and the control cores. This is likely due to the enzyme inhibitory effects of a lowered soil pH. Soil cores treated with urea did not show a statistically significant difference between ambient and lowered pH suggesting that urea increases the pH of soil when applied.

What does it mean?

The findings of this report highlight some of the complexities of practically managing N2O production from soil. In addition to pH other soil parameters such as; soil water content, temperature, aeration, organic content, mineral N availability and soil texture have an effect on N2O production. These parameters not only have an effect individually but also combine and interact in ways which are challenging to model. The best approach for effective mitigation of N2O is arguably to carry out case-by-case mitigation strategies as opposed to broad scale guidelines offered by bodies such as the IPCC. However, the challenge really lies in incentivising land owners to carry out such assessments which may seem to them to involve additional cost and little economic return.

How can I read the full report?

The full thesis is available to download here.