Nitrogen fertilizer: Climate’s friend or foe?

In this century, enough food production for everyone is a great challenge because of the growing global population. 

By 2050, we'll have an estimated 9-10 billion mouths to feed. That is why nitrogen fertilizer inputs to agriculture have been applied widely to meet the food demand all over the world and 2 billion already rely on fertilizer.

Fertilizer and reactive nitrogen have been used in farming to enhance yields. These fertilizer and reactive nitrogen have many negative impacts when used wrongly especially when farmers place too much or not enough quantity in the right place.

Farmers are not much concerned with the proper use of agricultural fertilizer and use a high amount of nitrogen fertilizer in their farms or lands. The efficiency of nitrogen used by plants is typically low (less than 50%). The excess nitrogen is converted to nitrous oxide (N2O) by soil microbes via denitrification. When there is rainfall, this nitrogen is going to waterways such as lakes, rivers, reservoirs, ponds, ditches and in the end the ocean.

The excess nitrogen can be transformed into ammonium (NH4+), Nitrate (NO3-) and Nitrite (NO2-). The ammonium dissolves into water easily and is responsible for the excessive growth of plants and algae in the waterways. Algal blooms are harmful to the aquatic vertebrate and invertebrate animals (especially to fish and shrimps) because it reduces the available amount of oxygen in the waterbody and it creates the dead zone in the waterbody. 

One of the important criteria of ammonium, not only it dissolves on the surface of freshwaters, but also in water droplets. When rain falls, it carries ammonium (NH4+) and reaches in the soil. Sensitive plants (mosses) and crops (tomatoes, cucumbers, fruit trees) are damaged by over fertilization. This ammonium contains rainfall are beneficial for grasses, but it changes the biodiversity of the ecosystem and soil acidification happens.

Water is essential to human beings. According to World Health Organization (WHO), a human can tolerate nitrate (50 mg/L as nitrate) and nitrite (3 mg/L as nitrite) at lower concentrations with no negative health impacts.pdf. The concentrations of nitrate and nitrite can, however, vary by season and can be higher in some areas where there are large discharges of agricultural fertilizer runoff. 

It is well known that nitrogen fertilizer is the key contributor to global warming. One of the studies revealed that Nitrous oxide (N2O) is a powerful greenhouse gas almost 300 times more powerful than the most common greenhouse gas (CO2).

Most of the agricultural nitrogen loss originates from fertilizer application. Therefore, in order to improve nitrogen use in agriculture to increase yields, we have to manage fertilisers in a more efficient way. We have to reduce the nitrogen emissions and the right amount of fertilizer in the right place at the right time.

 

Photo credit: Daily Pakistan