GROWER 101: Nutrient Disorders in Greenhouse Crops, Part II
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.
Ammonium Toxicity.In older plants with floral buds, margins of leaves curl upward or downwarddepending on the plant species. Older leaves develop chlorosis. The form ofchlorosis is variable and depends on the plant species. Necrosis followschlorosis on older leaves. Fewer roots form, and in advanced toxicities, roottips become necrotic, often with an orange-brown color.
With seedlings and bedding plants, young leaves developchlorosis, most often in an interveinal pattern, and margins curl up or downdepending on species.
Potassium Deficiency.The margins of older leaves become chlorotic followed by immediate necrosis.Similar necrotic spots may form across the blades of older leaves but more sotoward the margin. Soon, the older leaves become totally necrotic. Seedlingsand young bedding plants, prior to the formation of chlorosis and necrosis onolder foliage, are more compact and deeper green than normal.
Some foliage plants will develop oily spots on theundersides of older leaves that then become necrotic.
Calcium Deficiency.Symptoms are expressed at the top of the plant. Young leaves may developvariable patterns of chlorosis and distortion such as dwarfing, strap-likeshape or crinkling. Edges of leaves may become necrotic; shoots stop growing;petals or flower stems may collapse; and roots are short, thickened andbranched.
The older leaves of foliage plants may become thick andbrittle. In Philodendron scandens subspecies oxycardium and in Epipremnumaureum calcium has symptoms of a mobile nutrient. Yellow spots occur in thebasal half of older leaves. These spots enlarge into irregular, yellow areascontaining numerous, scattered, oil-soaked spots.
Sulfur Deficiency.Foliage over the entire plant becomes uniformly chlorotic. Sometimes thesymptoms tend to be more pronounced toward the top of the plant. While symptomson the individual leaf look like those of nitrogen deficiency, it is easy todistinguish sulfur deficiency from nitrogen deficiency because nitrogendeficiency begins in the lowest leaves.
Manganese Deficiency.Young leaves develop interveinal chlorosis, sometimes followed by the formationof tan spots in the chlorotic areas between the veins.
Manganese toxicity.Toxicity very often begins with interveinal chlorosis of young leaves due toiron deficiency caused by high manganese antagonism of iron uptake. Manganesetoxicity takes the form of burning Á of the tips and margins of olderleaves or formation of reddish-brown spots on older leaves. The spots areinitially about 1/16 inch (1-2 mm) in diameter and are scattered over the leaf.Spots become more numerous and eventually coalesce into patches.
Zinc Deficiency.Young leaves are small, and internodes are short, giving the stem a rosetteappearance. These leaves are also chlorotic in varying patterns but tend towardinterveinal. In kalanchoe, zinc deficiency can express itself as a fasciation(a flattened, highly branched stem).
Copper Deficiency.Young leaves develop interveinal chlorosis; however, the tips and lobes ofthese leaves may remain green. Next, the youngest, fully expanded leavesrapidly become necrotic. The sudden death of these leaves resemblesdesiccation.
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