Dr. Cliff Snyder

Reducing nitrous oxide emissions and nitrogen losses from fields with the 4Rs

Dr. Cliff Snyder, IPNI’s Nitrogen Program Director, explains the importance of implementing best management practices to reduce nitrogen (N) losses, and reduce nitrous oxide emissions from farm fields.

IFA: Why is it important to reduce nitrous oxide emissions?
Dr. Snyder
:Nitrous oxide is one of the three leading greenhouse gases (carbon dioxide, methane, and nitrous oxide) which contribute to global warming and climate change. It has a warming effect (radiative forcing) about 300 times that of an equivalent mass of carbon dioxide. Nitrous oxide has long atmospheric lifetime (about 120 years) and is the most significant emissions contributor to depletion of the ozone layer in our stratosphere.

Global emissions of nitrous oxide have been increasing. Emissions are estimated to be about 20% higher than what they have been over many past centuries. About 2/3 of the human-induced emissions originate from agriculture.

It is important to recognize that annual emission of nitrous oxide from most farm fields represents a nitrogen loss equivalent to less than 1 to 2 % of the applied nitrogen. Because fertilizer nitrogen (and manure) use is increasing globally, many believe there is a greater likelihood that nitrous oxide emissions will also increase, unless mitigation practices are more widely implemented.

IFA: Does an increase of Nitrogen Use Efficiency (NUE) result automatically in a reduction of nitrous oxide emissions?
Dr. Snyder
: Improved crop or cropping system recovery of the applied nitrogen (one expression of nitrogen use efficiency) usually results in reduced risks of loss of nitrogen from fields via all the major nitrogen loss pathways (nitrate leaching, drainage, runoff; ammonia volatilization; nitrous oxide emissions; di-nitrogen emissions). Yet, because of the episodic and pulsed nature of nitrous oxide emissions - and the number and complexity of management and environmental factors affecting emissions – we have learned that increasing crop recovery of applied nitrogen may not, on its own, always reduce nitrous oxide emissions.

A clearer understanding of the local climate, weather, and soil conditions - and their dominating influence on the soil nitrification and denitrification processes that affect nitrous oxide emissions – can help us better optimize the 4R management (right source, rate, time, and place) of nitrogen application, to help minimize the direct and indirect losses of nitrogen as nitrous oxide.

IFA: What is the optimal way to ensure a high NUE?
Dr. Snyder
: Crop nitrogen recovery by major cereal crops in most farmer’s fields averages about 40 percent at the global level, but research has helped us understand that we can raise that recovery to 60 to 70 percent through better cropping system, conservation practice, and 4R nutrient management implementation. These levels can also be reached by farmers adopting best management practices (BMPs). It is important that other essential nutrients (P, K, secondary nutrients, and micronutrients) are adequate and will not limit plant nutrition, or impair nitrogen use efficiency.

The optimal 4R nutrient management program will differ by soil, cropping system, and environmental conditions. There is no single, magical solution to reducing emissions of nitrous oxide; especially while also striving to reduce the loss of nitrogen via other important loss pathways. Nitrogen loss via those other pathways (which can contribute to indirect nitrous oxide emissions) is often greater and causes much larger economic impacts for the farmer and his/her local community. The expertise of skilled agronomists and crop advisers is needed to help identify improved nitrogen management opportunities on a field-by-field basis in order to improve and sustain crop yields, soil fertility and productivity, and farm profitability; while minimizing all nitrogen losses, including nitrous oxide.An important example of fertilizer industry leadership in view of these considerations, is the Nitrous Oxide Emissions Reduction Protocol (NERP), initiated by Fertilizer Canada (formerly the Canadian Fertilizer Institute). NERP aims to reduce on-farm emissions of nitrous oxide in a verifiable way that allows farmers to earn carbon credits. The protocol, based on the 4Rs, is being deployed in the Province of Alberta.

Find out more about 4R Nitrogen practices by reading IPNI’s new Issue Review entitled “Suites of 4R Nitrogen Practices for Sustainable Crop Production and Environmental Protection”, available here.

About Dr. Snyder:

Dr. Cliff Snyder is the Nitrogen Program Director for the International Plant Nutrition Institute (IPNI); and coordinates efforts to address environmental nitrogen challenges. He previously served as Midsouth and Southeast Director for the Potash & Phosphate Institute; and as state Extension Soils Specialist with the University of Arkansas. Cliff is a Fellow in the Soil Science Society of America and the American Society of Agronomy; and is a CCA. He received a Ph.D. in Soil Science and Forestry at North Carolina State University; and a M.S. in Agronomy (soil fertility) and B.S. in Agriculture (soil science) at the University of Arkansas.