Agriculture Reference
In-Depth Information
6
Nitrogen Interaction with
Other Nutrients
6.1 INTRODUCTION
Among the 17 essential plant nutrients, nitrogen plays the most important role in augmenting
agricultural production and potential environmental risks and impacting human and animal
health (Aulakh and Malhi, 2005). Nitrogen fertilization significantly influences crop yields in
low-fertility soils, especially in soils having low organic matter content and low cation exchange
capacity. The positive influence of N on crop growth also influences the uptake of other essential
nutrients, known as nutrient interaction. Interactions among nutrients occur when the supply of
one nutrient affects the absorption, distribution, or function of another nutrient in crop plants
(Robson and Pitman, 1983). In crop production, nutrient interactions assume added significance
by affecting the crop productivity and returns from investments made by farmers in fertilizers
(Aulakh and Malhi, 2005).
Nutrient interaction in crop plants is probably one of the most important factors affecting yields
of annual crops. Nutrient interaction may be positive (synergistic), negative (antagonistic), and no
interaction (Fageria, 1983; Fageria et al., 2011a). Aulakh and Malhi (2005) stated that nutrient inter-
actions have a role to play in determining the course and outcome of two major issues of interest in
fertilizer management, namely, balanced fertilizer input and efficient fertilizer use. Wilkinson et al.
(2000) reviewed the literature on nutrient interactions in soil and plant and stated that if two nutri-
ents are limiting, or nearly limiting growth or concentration in the plant tissue, where adding only
one of the nutrients has little effect while adding both gives a considerable effect, the effect is said
to be a positive interaction. It can be measured in terms of crop growth and nutrient concentrations
in the plant tissue. These authors further reported that if adding the two together has less effect than
when each is added separately, the effect is said to be a negative interaction. When the factors acting
in concert result in a positive growth response that is greater than the sum of their individual effects,
the interaction is positive or synergistic; when it is less than the sum of the individual effects, the
interaction is negative or antagonistic; and when it is the same, there is no interaction.
Soil, plant, and climatic factors can influence interaction. In the nutrient interaction studies, all
other factors should be at an optimum level except the variation in the level of the nutrient under
investigation. Hence, nutrient interaction results are valid only when other environmental factors
are at optimum levels, except the variation in the concentrations of the two nutrients under inves-
tigation. Wallace (1990) proposed the law of maximum in nutrient interaction studies rather than
Liebig's law of minimum. The law of maximum states that, when the need is fully satisfied for
every factor involved in the process, the rate of the process can be at its maximum potential, which
is greater than the sum of its parts because of the sequentially additive interaction (Wallace, 1990).
Nutrient interaction can occur at the root surface or within the plant. Interactions at the root sur-
face are due to the formation of chemical bonds by ions and precipitation or complexes. One exam-
ple of this type of interaction is that the liming of acid soils decreases the concentration of almost
all the micronutrients except molybdenum (Fageria and Zimmermannn, 1998; Fageria, 2000). The
second type of interaction is between ions whose chemical properties are sufficiently similar that
they compete for the site of absorption, transport, and function on the plant root surface or within
plant tissues. Such interactions are more common between nutrients of similar size, charge, and
geometry of coordination and electronic configuration (Robson and Pitman, 1983).
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