Agriculture Reference
In-Depth Information
Chapter 9
Nutrient Use and Nutrient Use Efficiency
of Crops in a High CO
2
Atmosphere
Sabine Tausz-Posch, Roger Armstrong, and Michael Tausz
Abstract Atmospheric CO
2
concentrations [CO
2
] are continually increasing and
are predicted to reach ~550
μ
mol mol
1
by 2050, about a 40 % increase from 2013
levels. Such a large increase in one of the key resources for plant growth will have
significant effects on all plants, as carbon assimilation and, consequently, growth
and yield is stimulated by the so-called
. The one sided
increase in carbohydrate acquisition leads to changes in the chemical composition
of plants: despite decreases in nutrient concentrations in plant tissues, the greater
biomass developed by crops under elevated [CO
2
] could lead to increased nutrient
demand. Nutrient use efficiency in terms of yield divided by available nutrient may
improve, but grains or vegetative plant parts have decreased protein and mineral
nutrient concentrations, which can diminish market and nutritious value. A number
of hypotheses have been proposed to explain the decreases in nutrient concentra-
tions, among them: (1) Dilution by increased biomass, (2) decreased mass flow,
(3) changes in root architecture and function, (4) decreased nitrate reduction, and
(5) changes in nutrient allocation and remobilisation. In addition, elevated [CO
2
]is
likely to change soil processes, including nutrient supply. The extent to which some
or all of these contribute to changes in crop nutrition and yield quality is currently
unknown because most have not been sufficiently tested under relevant field
conditions. This chapter gives an overview of the changes in plant nutrition and
trade-offs under elevated [CO
2
] to point out that current and future efforts towards
improved plant nutrient efficiency should explicitly take into consideration rising
[CO
2
]. In particular, field testing of putative nutrient use efficiency traits and
nutrient management strategies should include elevated [CO
2
] as a relevant factor
in suitable exposure systems such as Free Air CO
2
Enrichment (FACE) technology.
CO
2
fertilisation effect
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