Diagnostics and symptoms of potassium deficiency in crops

Risk zones and general symptoms of potassium deficiency

Potassium determines the resistance of plants to lodging and also directly affects the quality and storage life of the harvest. Deficiency of this element most often occurs in light soils — sandy and sandy-loam, as well as in peatlands and river floodplains. Humic, calcareous, and heavily limed loamy soils of the Non-Chernozem zone are also at risk.

Starvation symptoms usually appear during periods of intense nutrient uptake. Older leaves are always the first to suffer, as the plant redirects potassium from them to younger growing organs. Signs of deficiency are easy to identify during a visual inspection of the field.

• slowed growth rates and shortened stems;
• marginal "burn" (yellowing, browning, and death of leaf edges and tips);
• wrinkling of leaf blades and the appearance of a bluish-green color;
• formation of a thin, loose stem;
• lodging of crops.

Indicator plants react fastest to potassium deficiency. These include potato, beet, cabbage, bean, gooseberry, red currant, and apple. By monitoring the condition of these crops, one can notice a nutrient deficiency on the farm in time.

How potassium deficiency manifests in different crops

In grain legumes, signs of starvation begin with the lower leaves — their edges turn yellow, then brown and die off. In beans, the leaves additionally wrinkle, take on a dome shape, and their edges curl downwards, with tissue death starting from the central leaflet. In peas, before the edges dry out completely, many small brown and tan spots appear on the lightened areas.

With potassium deficiency, potato leaves acquire an abnormal dark green color, become wrinkled and dome-shaped, and are covered with small brown spots with a bronze sheen. Older foliage turns yellow and brown from the tips to the center, its edges curl downwards and break off easily, while a tuft of healthy green leaves remains on the top of the bush for a long time. The bush itself becomes spreading, internodes shorten, and the haulm dries out prematurely.

In tomatoes, potassium deficiency hinders bush growth and fruit ripening, severely reducing overall yield. Young leaves wrinkle and acquire a bluish-green tint, while the lower ones first turn gray, then their edges yellow and brown, after which the leaves fall off. Stems become woody, roots develop poorly, and fruits ripen unevenly, becoming covered with green and yellow spots.

Cabbage signals a lack of potassium with wavy leaves with a bluish tint. A slight interveinal chlorosis and marginal burn appear on them, where the burnt edges curl upwards and the leaves themselves downwards, impairing head growth. In cucumbers, leaves also become dome-shaped and dark green, with a dying bronze margin. Cucumber fruits thus acquire a characteristic pear-like shape with an enlarged tip.

In onions, the tips of old leaves become grayish-yellow or straw-colored. Leaves take on a velvety appearance, twist into a spiral, and gradually dry out towards the base. Radish, under potassium deficiency, forms leathery, thick leaves with a dark green center and browned, curled edges, and its root vegetables swell unnaturally.

In orchards and berry patches, potassium starvation manifests as a marginal "burn" of leaves of various colors — from bluish-green to crimson. The symptom appears after the shoots have grown a few centimeters. The burn starts from the middle of the shoot and spreads towards its base and tip. Affected leaves do not fall off for a long time, crack from the wind, and the crumbling dry tissue forms jagged edges and holes.

In some garden crops, symptoms have their own specifics:

• in cherry, leaves fold into a boat shape upwards along the main vein, and their dead edges also curl upwards;
• in raspberry, leaves wrinkle and curl heavily, and the dried edges curl downwards;
• in grapevine, lower leaves turn yellow (chlorosis) or become bluish-purple, starting from the tip and edges, after which they dry out prematurely, and clusters and berries grow small.