Cucumber leaves getting crispy
This is likely an iron deficiency. Iron is needed to produce chlorophyll and to activate several enzymes, especially those involved in photosynthesis and respiration. Deficiencies of iron are more likely in alkaline or calcareous soils, and can be induced by over-liming, poor drainage, or high concentrations of metallic ions in the soil or nutrient solution. Iron availability decreases at pH above 7. Manganese toxicity can induce an iron deficiency. Iron deficiency causes a uniform pale green chlorosis of the newest leaves; all other leaves remain dark green. Initially, the veins remain green, which gives a net-like pattern. If the deficiency is severe, the minor veins also fade, and the leaves may eventually burn, especially if exposed to strong sunlight. Good drainage and soil aeration favor iron availability. Foliar sprays of iron sulphate (150 g/100 L) can be used to treat symptoms, but symptoms will return if the sprays are discontinued. The best long-term action is to correct soil chemical and physical problems.
For crops grown in soilless media, use a nutrient solution containing 2–3 ppm Fe. Iron chelates are generally less likely to precipitate under alkaline conditions and are normally preferred in hydroponic solutions.
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