Nitrogen application rate appears to be the most important criteria for optimizing crop productivity in terms of agronomic performance, cost efficiency and sustainability, says a Saskatchewan research team. However, more doesn't necessarily mean better.

"Economic concerns caused by low crop prices and high nitrogen fertilizer input costs, as well as environmental issues such as leaching and gaseous losses to the atmosphere are driving research efforts to increase nitrogen management efficiency," says Dr. Jeffrey Schoenau, a research scientist with the University of Saskatchewan in Saskatoon.

As part of a team of public and private sector researchers, Schoenau recently completed a three-year comparative study of the effects of various nitrogen management practices on agronomic performance in wheat, canola and flax, and on environmental sustainability.

Supported in part by the Endowment Fund administered by Western Grains Research Foundation, the research also included calculations of total energy budgets (input versus output) for various fertilizer placement/formulation combinations.

Four Saskatchewan locations, Star City, Indian Head, Scott and Swift Current, were included in the study. Researchers evaluated side band and mid-row band at seeding, pre-plant fall band and spring broadcast placement methods of urea and anhydrous ammonia fertilizer at various rates. They also measured emissions of the greenhouse gas nitrous oxide associated with the different practices.

"Nitrogen rate, independent of distribution method or formulation, had the most profound impact on crop performance, energy budget, as well as nitrous oxide gas emissions," says Schoenau. "Applying nitrogen at the recommended rate specific for crop, soil and climatic conditions is an efficient management approach for producers."

Of the three crops studied, flax tended to be least responsive to nitrogen management. This could be due to a difference in nitrogen demand by the crop and or its ability to access soil nitrogen, he says.

Overall, there was no major difference between the side and mid-row banding fertilizer application techniques on crop yield or quality, and both were considered effective methods of fertilizer placement in single pass seeding-fertilizing system, says Schoenau. However, fall-banded nitrogen and broadcasted urea tended to be less efficient than spring-banded applications from both agronomic and energy budget perspectives.

"Generally, soil moisture at the time of fertilizer application appeared to be the key factor influencing the effect of method and fertilizer formulation on crop performance," says Schoenau. In some years of the study, very dry soil conditions in the fall likely affected losses of ammonia in the fall banding treatments.

Urea and anhydrous ammonia generally performed equally well, whether side or mid-row banded, he says. However, increased production and transportation costs for urea made anhydrous ammonia treatments the favoured option.

Measurements of nitrous oxide gas emissions showed that the proportion of nitrogen lost from urea and anhydrous ammonia fertilizer was lower than previous estimates and did not appear to be clearly related to formulation or placement, says Schoenau. Emissions were directly related to fertilizer rate.

A report on this research can be found on the Western Grains Research Foundation (WGRF) Web site at www.westerngrains.com.

WGRF is the largest farmer funded and directed grains research funding organization in Western Canada. WGRF allocates approximately $5 million annually to research through the Wheat and Barley Check-off Funds, and the separate Endowment Fund.