Crop Guide: Nutritional recommendations for Cucumber - Haifa-Group

Figure 3.4: Left: Completely stunted and
pale plant that has not received any N after
germination
Center: A healthy plant.
Right: A plant that received less N than the
center one. Older leaves turn pale green to
yellow; this discoloration spreads to younger
leaves up the plant.
Both vegetative growth and fruit production are severely restricted when nitrogen supply is
inadequate. Plants appear pale and spindly. New leaves are small but remain green, whereas the
oldest leaves turn yellow and die. If the problem is not corrected, the
yellowing spreads up the shoot to younger leaves. Yield is reduced
and fruit are pale, short and thick.
Treatment
In soil-grown crops: side-dress with 20–50 kg/ha of N, or apply
fortnightly foliar sprays of 2% urea at high volume. To prevent
possible salt burn to leaves when applying any foliar spray, spray late
in the afternoon or during cloudy weather.
For crops grown in soilless media, use a nutrient solution containing
150–200 ppm N.
3.2.3 Excessive nitrogen
Plants given slightly too much nitrogen show excessive growth and
a softer plant; leaves will be darker green and sometimes thickened
and brittle.
Plants given highly too much nitrogen are generally stunted and
have strong, thick stems, short internodes, a mass of tendrils, short
side shoots, fewer flowers, and small fruit. The middle and older
leaves cup downwards and wilt easily in warm conditions. Leaf
28
Figure 3.5: Nitrogen deficient cucumber fruit
is misshapen and chlorotic.
Figure 3.6: Symptoms of
excessive nitrogen include
wilting and downward cupping
of the older leaves, followed by
yellow and brown burnt areas
on lower leaves.