Intelligent Fertilisers Reduce Agricultural Pollution Graeme Nicol

 Original source : Polytechnique Insight

Since the 19th century we know that certain microorganisms play a key role in the nitrogen cycle. They are responsible for carrying out essential steps in the process, producing different forms of nitrogen that can be used by plants. Nitrogen-based fertilisers used in agriculture accelerate this cycle with major environmental and economic consequences. Thus, an ‘intelligent’, slow and progressive distribution of nitrogen could be used to limit many of these negative effects.

Fertilisers put nitrogen into soil

Plants need nitrogen to grow, using either ammonium or nitrate (nitrogen-rich molecules) as a source. Ammonium finds its way naturally into soil at a rate of 110 million tonnes per year. This happens through deposition after lightning and the death of organic material, but mainly via the fixation of nitrogen from the atmosphere such as in the nodules of leguminous plants. Nitrate, however, is the result of conversion from ammonium by microorganisms. 

Even though plants can take up both, it is the conversion of ammonium to nitrate, which has major consequences on agricultural systems. Vast quantities of nitrogen (an additional 100 million tonnes per year) added to soil in the form of fertilisers accelerates microbial activity, resulting in the overproduction of nitrate from ammonium.

This excess nitrate is responsible for the negative environmental impact because it makes the nitrogen more mobile, increasing its pollution potential by allowing it to move out of the soil in water or even into the air. Nitrate pollution in runoff water, groundwater and rivers encourages algal blooms and contaminates drinking water. It also leads to substantial increases in the emission of nitrous oxide (N2O), the third most important greenhouse gas, concentrations of which have increased by 20% since pre-industrial times. N2O is also tipped as the compound primarily responsible for depletion of stratospheric ozone in the 21st Century. 

Intelligent fertilisers: a smart solution

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April 22nd, 2021