Agriculture Reference
In-Depth Information
their concentration in plant tissues (macro- and micronutrients), and the specific
roles they fulfil in the plant
s metabolism are as diverse as their physiochemical
'
properties (Marschner
2012
).
Plant NUE is a term, which describes a highly complex, multigenic trait with
various interconnected physiological processes involved and modified by numerous
factors. Consequently, there are numerous approaches to define, analyse and pos-
sibly improve NUE. For a long time it has been known that the ability of plants to
utilize nutrients can differ substantially between species and cultivars, and that this
could be the basis for further improvement through breeding (Gerloff
1963
; Shea
et al.
1968
; Siddiqi and Glass
1981
). In order to develop a common framework for
NUE, scientists started to formulate concepts and definitions that should serve as a
basis for comparison and discussion of research. Since then countless studies in
various scientific disciplines dealing with different plant species, in different
contexts, under different conditions and focusing on different nutrients failed to
find one definition of NUE that describes all cases satisfactory but rather revealed
that the issue is too complex to do so.
In this chapter the definition of NUE will be discussed from a whole plant
perspective. It starts with the transfer of NUE from an ecological to an agronomical
context and the different levels of organization on which it can be discussed. This is
followed by a brief introduction into the conceptual framework of NUE, especially
for nitrogen (N) and equipped with these theoretical concepts the attention of the
reader will be drawn to the concrete physiological basis of NUE. These processes
are the targets of potential improvement of NUE for agricultural production by
modern breeding. However, how relevant a certain physiological process is in a
particular cropping system depends on three main variables: environment, plant and
nutrient, which influence the physiological basis of NUE. The last parts of this
chapter are dedicated to the need to improve NUE in modern agriculture and ends
with a critical review of the chances and challenges to improve plant NUE from a
whole plant perspective.
Nutrient Use Efficiency - Contexts and Concepts
A general definition of “efficiency” is:
The achievement of an intended outcome
with a lowest possible input of costs
. While the input in the concept of NUE
obviously is nutrients, the
intended outcome
needs to be further specified. This
can happen in different ways, which leads to many different versions of what NUE
actually means and how it can be improved. Very fundamental is the difference
between an ecological and agronomical context. Understanding this difference is
crucial to develop strategies of improving a plant with its complex ecophysiological
background in the straightforward input-output system of agriculture.
The environment of a plant is far from being a stationary equilibrium. Arising
from the way our planet turns around its own axis and follows its orbit around the
sun, all abiotic and biotic factors on its surface underlie oscillations over time and
all forms of living organisms are forced to adapt to the local oscillations in their
