Agriculture Reference
In-Depth Information
8
Management Practices
to Improve Nitrogen Use
Eficiency in Crop Plants
8.1 INTRODUCTION
The use of nitrogen (N) is one of the most important single factors in increasing crop productivity
in the last half century. The past 60 years have brought marked advances in the capacity to manu-
facture and apply plant-available N as commercial fertilizers. These advances, however, have not
diminished the importance of problems related to N management but have created a greater appre-
ciation of the importance of avoiding yield-limiting N deficiencies (Blackmer, 2000). Close correla-
tions are commonly found between historical crop yields and annual N application rates (Sinclair
and Horie, 1989). Similarly, Fageria and Baligar (2005) reported that N is the most limiting nutrient
for crop production in many of the world's agricultural areas and its efficient use is important for the
economic sustainability of cropping systems. Adopting appropriate nitrogen management practices
is essential to improve N use efficiency in crop plants. Further, it also promotes the sustainability of
cropping systems. In addition, the dynamic nature of N and its propensity for loss from soil-plant
systems creates a unique and challenging environment for its efficient management. Adequate N
management practices to improve its efficiency involve soil management factors, nitrogen fertilizer
management factors, crop management factors, and plant management factors. Hence, the nitrogen
economy of crop production involves considerable complexity due to the involvement of several
factors and their interactions. Some of these practices are already mentioned in other chapters, and
hence there is duplication. However, some duplication is unavoidable due to the importance of some
practices in some of the other chapters.
Appropriate N management practices are essential not only to improve crop yields and reduce
the cost of production, but its effective management is also related to the reduction of environmental
pollution. Culman et al. (2013) reported that a major goal of current agronomic research is to make
annual grain crop production more sustainable, with management strategies that supply adequate
fertility to meet crop demand while conserving soil and water quality. Environmental pollution by
N involved the contamination of groundwater by
NO
−
and also greenhouse gases such as NO and
N
2
O. Nitric oxide, which is the dominant component of the so-called NO
x
, has no direct effect on
the earth's radiation balance, but it is very active chemically and plays a critical role in its interaction
with oxidants such as ozone (Campbell et al., 1995). Because NO
x
is eventually oxidized to nitric
acid, it will also contribute to acid precipitation.
Modern agricultural technologies are often responsible for increased emissions of gases caus-
ing atmospheric pollution (especially N
2
O and CH
4
), and agriculture accounts for an estimated
84% of global anthropogenic N
2
O emissions (Smith et al., 2008). Pang et al. (2009) also reported
that agricultural soils are known to be responsible for a large proportion (70-81%) of the increase
in N
2
O emissions to the atmosphere, mainly due to the use of nitrogen fertilizer. Nitrous oxide is
mainly produced in the soil by nitrification and denitrification, which are particularly controlled
by the soil water-filled pore space, soil temperature, availability of labile organic carbon, soil pH,
and the proportion and amount of ammonium and nitrate present (Bouwman, 1998; Dobbie and
Smith, 2003; Martins et al., 2003; Pang et al., 2009).
N
3
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