All plants need nitrogen, an essential nutrient for growth. Through the years, growers have found ways to replace nitrogen removed from soil, improve nutrient uptake and increase yields through ever-improving fertilizer management. The new challenge? Meeting each of these goals, and more.

Moved by a growing spirit of environmental stewardship, or in some cases, new government requirements, producers seek to limit nutrients in the environment through improved fertilizer efficiency. New products, such as inhibitors and controlled-release nitrogen, supply tools to follow the 4R stewardship initiative discussed in the December 2009 issue of Partners. (Click here for article.)

A popular topic today is excess nutrients in the environment. From the Gulf of Mexico to the Chesapeake Bay, the Great Lakes to the Pacific Northwest, policymakers look to agriculture to improve water quality and help reduce nutrients in ground and surface water.

Many conventional nitrogen application methods apply fertilizer in advance of crop needs. The delay between nitrogen application and crop uptake increases the chance for environmental losses through leaching, volatilization, and denitrification.

* Leaching: the movement of plant nutrients in the soil solution below the root zone. This occurs most frequently in coarse-textured, cracked or sandy soils, during higher levels of precipitation or irrigation, with excessively applied fertilizers, or with a limited plant root zone.
* Volatilization: the loss of nitrogen to the atmosphere as ammonia gas. This most often happens when producers apply nitrogen on the soil surface in the organic form of urea, and do not incorporate it quickly.
* Denitrification: anaerobic microorganisms strip the oxygen from nitrate, producing nitrogen gas, nitric oxide or nitrous oxide, which releases to the atmosphere. This occurs in wet and compacted soils, and in warm soil temperatures, with readily decomposable organic matter present.

Factors affecting each loss mechanism are different, but they each provide two results: decreased profits for the producer, through lost inputs and lower yields; and possible negative impacts on the environment, through lost nutrients.

Under severe conditions, these impacts can be costly for the producer. When conditions conducive to nitrogen loss occur, applying the right source at the right rate, time and place is even more important.

Under conventional practices, all urea applied to the soil converts to ammonium (NH4+) within several days. Depending on soil conditions, NH4+ can be converted either to the mobile nitrate (NO3-) form, which can be subject to both leaching and denitrification, or the gaseous ammonia (NH3) form, subject to volatilization. The rapid conversion of urea to these different forms allows for significant losses of applied nitrogen.

A variety of fertilization practices reduce nitrogen losses and increase its efficiency.

Products such as Agrotain®, a urease inhibitor, and N-Serve®, a nitrification inhibitor, slow down the conversion processes, reducing the amount of volatilization, leaching and denitrification.

Slow and controlled fertilizer products, such as ESN®, produced by Agrium Advanced Technologies, help maximize nitrogen-use efficiency in an environmentally friendly way.

The products reduce nitrogen loss by delivering nitrogen when the crop needs it, instead of all at once, as with

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About the writer: Matthew W. Clover, Ph.D., is a Midwest agronomist for Agrium Advanced Technologies, based in Loveland, Colo.

The views expressed in the Member's Column do not necessarily reflect the views of the Conservation Technology Information Center.