The Effect of Nitrogen Fertilizer on Soil Micro-organisms

John Harvard and Andries Robertson states “that nitrogenous fertilizer has no effect on their soil fertility and crop production is on a rise”. If that was true, it would count as a major environmental benefit of synthetic nitrogen use.

At a time of climate chaos and ever-growing global greenhouse gas emissions, anything that helps vast swaths of farmland sponge up carbon would be a stabilizing force. Moreover, carbon-rich soils store nutrients and have the potential to remain fertile over time–a boon for future generations (Philpott, New research: synthetic nitrogen destroys soil carbon, undermines soil health, 2010). Dousing farm fields with synthetic nitrogen make plants grow bigger and faster. As plants grow, they pull carbon dioxide from the atmosphere. Parts of remove plants are harvested as crop but the remainder, stays in the field and ultimately becomes soil. In this way, some of the carbon gobbled up by the nitrogen enhanced plants stays in the ground and out of the atmosphere (Philpott, New research: synthetic nitrogen destroys soil carbon, undermines soil health, 2010).

Well, that logic has come under fierce challenge from a team of University of Illinois researchers led by professors Richard Mulvaney, Saeed Khan, and Tim Ellsworth. In two recent papers the trio argue that the net effect of synthetic nitrogen use is to reduce soil’s organic matter content. Why? Because, they posit, nitrogen fertilizer stimulates soil microbes, which feast on organic matter.

Over time, the impact of this enhanced microbial appetite outweighs the benefits of more crop residues (Philpott, New research: synthetic nitrogen destroys soil carbon, undermines soil health, 2010). And their analysis gets more alarming. Synthetic nitrogen use, they argue, creates a kind of treadmill effect. As organic matter dissipates, soil’s ability to store organic nitrogen declines. A large amount of nitrogen then leaches away, fouling ground water in the form of nitrates, and entering the atmosphere as nitrous oxide (N2O), a greenhouse gas with some 300 times the heat-trapping power of carbon dioxide (Philpott, New research: synthetic nitrogen destroys soil carbon, undermines soil health, 2010). In Guyana, the use of nitrogen fertilizers has become an essential and routine part of many crop production systems.

Particularly in Parika, farmers produced crops for market sales on a weekly basis which shows the frequent use of nitrogen fertilizers. Farmers here do not use nitrogen fertilizers just to grow big crops or to increase nutrient content of their soils; they do it to make a living. Therefore, it is imperative that a research be conducted to show the effects of these fertilizers and make recommendations to improve the habitat of soil microorganisms.