Magnesium Deficiency of Cucurbit Crops
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Magnesium deficiency symptoms first appear as yellowing between the leaf veins (interveinal chlorosis), beginning on the oldest leaves and slowly spreading to newer growth. Yellowed tissues may turn brown, die, and drop out, giving the leaf a shot-hole pattern. Magnesium deficiency usually appears during periods of rapid growth, when the fruit is enlarging. This deficiency is more likely to occur in plantings on sandy soils with a low pH, especially in dry years. Sandy soils often have a low cation exchange capacity and may not contain adequate levels of magnesium. Deficiency symptoms are more commonly observed in muskmelon than in other cucurbits.
Magnesium deficiency on muskmelon leaves.
(Photo: Terry Jones, University of Kentucky)
Management:
- Maintain the soil pH near 6.5.
- Soil test results should show at least 200 lb of magnesium/acre.
- Potential sources of preplant magnesium include magnesium oxide and dolomitic lime.
- If necessary, fertigate Epsom salts (magnesium sulfate) and magnesium oxide through a drip irrigation system.
- Avoid heavy applications of fertilizers containing competing cations (K+, Ca++, NH4++).
- Foliar sprays are generally ineffective in correcting significant deficiencies.
