Diagnostic Techniques for Nitrogen Requirements in Crop Plants - Nitrogen Management in Crop Production - page 121

Corn

Dry bean

0 mg N kg -1

200 mg N kg -1

0 mg N kg -1 200 mg N kg -1

FIGURE 3.12 ( See color insert. ) Growth of dry bean and corn at two N levels grown on a Brazilian Oxisol.
Half of the N was applied at sowing and the remaining half at 35 days after sowing.

1982), reduces leaf expansion and leaf area (Radin and Matthews, 1989), increases starch and sol-
uble carbohydrates in roots (Radin et al., 1978), and decreases leaf osmotic and turgor potential
(Radin and Parker, 1979).

3.2.1.2 Toxicity Symptoms
When essential plant nutrients are absorbed in excess of plant requirement, they create adverse effects
on plant growth and development. Nitrogen is rarely toxic to crop plants when absorbed in excess
amount. However, when it is absorbed in higher amount than the required amount, it may creates an
imbalance with other essential nutrients. Bennett (1993) while describing general guidelines for critical,

Upland rice

300 mg N kg -1

0 mg N kg -1

BRA 02535

FIGURE 3.13 ( See color insert. ) Growth of upland rice genotype BRA 02535 at low and high N levels. Half
of the N was applied at sowing and the remaining half at the active tillering growth stage.