agronom.me
Menu

Nutrition and fertilizers

Signs of magnesium and calcium deficiency in the mineral nutrition of crops

For gardeners

3 min read

NUTRITION AND FERTILIZERS N

Magnesium deficiency directly blocks plant development and reduces yield. Most often, this problem occurs on sandy and sandy-loam sod-podzolic soils, red earths, and in horticulture — also on some loams. It is important for an agronomist to notice the first symptoms in time to adjust the nutrition system before critical leaf loss occurs.

Magnesium starvation is sharply aggravated by the application of high doses of potassium chloride, potash salt, and ammonium sulfate. Potassium and ammonium cations block the uptake of magnesium by the plant. The deficiency is also exacerbated in acidic soils, where magnesium shifts into an unavailable form and is quickly leached. To correct the situation, use liming and nitrate forms of nitrogen fertilizer.

The main sign of magnesium deficiency is interveinal chlorosis, which always begins with the lower leaves. The plant redirects mobile magnesium to young tops, which causes chlorophyll in older leaves to break down. The veins and the tissue adjacent to them remain bright green, while the leaf blade between them changes color.

Depending on the crop, the interveinal tissue colors differently:

  • in millet — into orange;
  • in cotton and blackcurrant — into purple-red;
  • in most other crops — into light green, greenish-yellow, or yellow.

During acute starvation, the tissue between the veins dies, covering itself with tan, brown, gray, or red spots. This spotted chlorosis gradually moves up the plant. Leaves fall off prematurely from the bottom up until only rosettes of thin, pale leaves remain at the ends of the shoots.

Indicator plants that react first to a lack of magnesium: potatoes, leaf cabbage, gooseberry, blackcurrant, and apple. Monitor their condition first.

How to recognize calcium deficiency in acidic soils

Calcium starvation is rare and usually manifests in acidic sandy and sandy-loam soils. The risk of deficiency increases with excessive application of potassium fertilizers, however, even in this case, signs of calcium shortage appear later than those of magnesium. Potatoes, vegetable, and fruit crops suffer most from the deficiency.

In potatoes, a lack of calcium strikes young terminal leaves: a light green stripe appears along their edges, which then dies. In severe cases, terminal buds perish, and young leaves do not even unfold. Leaf lobes curl with edges downward, and brown patches of dead tissue form in the pulp of the tubers.

Vegetable crops sharply slow their growth during calcium deficiency, forming thick, woody stems. New leaves grow chlorotic, while old ones remain green. A loss of turgor is observed in young shoots along with the death of terminal buds. The root system suffers greatly: root tips die and decay, and small spherical swellings form on the surviving sections.

In fruit and berry crops, the tips and edges of young terminal leaves or tissue along their midrib die off. The leaves become deformed, curving with their tips downward and their edges upward. Chlorotic stripes appear on their margins, with ragged contours and spotting along with brown "burns," after which the foliage drops. The tops of shoots (especially in apple trees) and growth points die, and damaged roots turn into thick, stunted stubs.

Read next