Magnesium deficiency (Mg)
A typical indicator of magnesium deficiency in vegetables is the bright yellow to orange-yellow chlorosis, which develops between the leaf veins. Prolonged deficiency will eventually lead to death of the tissue. Due to magnesium’s phloem mobility this will typically affect older leaves first. In monocotyledoneae (eg. onions, leeks), magnesium deficiency will show as spots and stripes, and is therefore frequently termed “striated chlorosis”. In dicotyledonous vegetable crops however, which includes nearly all vegetable crops except for onions, chlorosis will occur between the individual leaf veins. This will lead to the characteristic marbled appearance of the leaves. In contrast to potassium deficiency, chlorosis caused by magnesium deficiency will begin at the leaf stalk, moving on to leaf tips, while leaf veins will remain green for quite some time. This type of chlorosis is termed “interveinalchlorosis”.
Magnesium deficiency is becoming more widespread in vegetable production, particularly in crops such as bell peppers and tomatoes due to these plants’ extraordinarily high requirements. The colour of cabbage in case of magnesium deficiency depends on the variety and on the respective anthocyanin content. In melons, magnesium deficiency will only become obvious after fruit set, as is also the case with potassium deficiency. In legumes, such as in peas and beans, magnesium deficiency will often cause twisted i.e. retracted leaves, in addition to classic yellow discolouration.
In order to alleviate the effects of magnesium deficiency it is necessary to apply a balanced basal dressing, using ESTA® Kieserit or Patentkali® and incorporating it into the soil, if necessary. Within the course of the vegetation period, EPSO foliar fertilisers may be used regularly, together with plant protection treatments, in order to meet the peak requirements.