Agriculture Reference
In-Depth Information
CHAPTER 15
IMPROVING NITROGEN USE
EFFICIENCY IN CROPS FOR
SUSTAINABLE AGRICULTURE
BERTRAND HIREL, THIERRY T
É
TU, PETER J. LEA,
AND
FR
É
D
É
RIC DUBOIS
15.1 INTRODUCTION: SOCIOECONOMIC AND
ENVIRONMENTAL STAKES
Today, the main method to maintain or restore soil nutrients and increase
crop yields is the application of mineral fertilizers such as nitrogen (N).
The N used in commercial fertilizers is particularly soluble for easy up-
take and assimilation by plants. Because of the simplicity of its storage
and handling, N can easily be applied when plants need it most. Mineral
fertilizers are now the main source of nutrients applied to soils, even if the
contribution of animal manure remains important, especially when there is
densely populated livestock nearby. After World War II, N fertilizers have
been used extensively to increase crop yield. The use of synthetic N fertil-
izers has eliminated a major elemental constraint with respect to enriching
the soil stock of organic C and N originally managed by organic manure
