GROWER 101: Nutrient Disorders in Greenhouse Crops, Part II
Pinpoint greenhouse crop problems with this second of a two-part series identifying nutrient disorders.
As promised in last month’s issue, the second of GPN’s two-part series on nutrient disorder shows you symptoms associated with additional deficiencies and toxicities of nutrients in greenhouse crops. When assessing nutritional status, remember the four sets of information: irrigation water quality, root substrate tests, foliar analysis and visual symptomology. The deficiencies below will help you with visual symptomology.
In older plants with floral buds, margins of leaves curl upward or downward
depending on the plant species. Older leaves develop chlorosis. The form of
chlorosis is variable and depends on the plant species. Necrosis follows
chlorosis on older leaves. Fewer roots form, and in advanced toxicities, root
tips become necrotic, often with an orange-brown color.
With seedlings and bedding plants, young leaves develop
chlorosis, most often in an interveinal pattern, and margins curl up or down
depending on species.
The margins of older leaves become chlorotic followed by immediate necrosis.
Similar necrotic spots may form across the blades of older leaves but more so
toward the margin. Soon, the older leaves become totally necrotic. Seedlings
and young bedding plants, prior to the formation of chlorosis and necrosis on
older foliage, are more compact and deeper green than normal.
Some foliage plants will develop oily spots on the
undersides of older leaves that then become necrotic.
Symptoms are expressed at the top of the plant. Young leaves may develop
variable patterns of chlorosis and distortion such as dwarfing, strap-like
shape or crinkling. Edges of leaves may become necrotic; shoots stop growing;
petals or flower stems may collapse; and roots are short, thickened and
The older leaves of foliage plants may become thick and
brittle. In Philodendron scandens subspecies oxycardium and in Epipremnum
aureum calcium has symptoms of a mobile nutrient. Yellow spots occur in the
basal half of older leaves. These spots enlarge into irregular, yellow areas
containing numerous, scattered, oil-soaked spots.
Foliage over the entire plant becomes uniformly chlorotic. Sometimes the
symptoms tend to be more pronounced toward the top of the plant. While symptoms
on the individual leaf look like those of nitrogen deficiency, it is easy to
distinguish sulfur deficiency from nitrogen deficiency because nitrogen
deficiency begins in the lowest leaves.
Young leaves develop interveinal chlorosis, sometimes followed by the formation
of tan spots in the chlorotic areas between the veins.
Toxicity very often begins with interveinal chlorosis of young leaves due to
iron deficiency caused by high manganese antagonism of iron uptake. Manganese
toxicity takes the form of burning Á of the tips and margins of older
leaves or formation of reddish-brown spots on older leaves. The spots are
initially about 1/16 inch (1-2 mm) in diameter and are scattered over the leaf.
Spots become more numerous and eventually coalesce into patches.
Young leaves are small, and internodes are short, giving the stem a rosette
appearance. These leaves are also chlorotic in varying patterns but tend toward
interveinal. In kalanchoe, zinc deficiency can express itself as a fasciation
(a flattened, highly branched stem).
Young leaves develop interveinal chlorosis; however, the tips and lobes of
these leaves may remain green. Next, the youngest, fully expanded leaves
rapidly become necrotic. The sudden death of these leaves resembles
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