Nickel

Nickel (Ni) is a vital ultra-micronutrient for the healthy development of higher plants. Although the requirement for it is measured in micrograms, its biological role is critical for efficient nitrogen metabolism.

The primary function of nickel is to support the activity of the urease enzyme. This enzyme is essential for breaking down urea into ammonia and carbon dioxide, enabling plants to utilize nitrogen efficiently and preventing toxic accumulation of urea in plant tissues.

The element also participates in iron metabolism and supports normal seed germination. It has been established that nickel is necessary to activate enzymes responsible for resistance against certain pathogens and environmental stress factors.

Nickel is actively involved in the transport of nutrients across cell membranes. It influences the activity of hydrogenases involved in nitrogen fixation in legumes, thereby enhancing their symbiotic productivity.

In natural conditions, nickel is almost always present in soils in sufficient quantities. However, its bioavailability may decrease at high pH levels, making application in the form of chelates or soluble salts advisable in intensive agricultural systems.

Nickel deficiency is most pronounced in cereal and legume crops. The main indicator of a shortage is reduced activity of the urease enzyme, leading to the accumulation of urea in leaf tissues.

Symptoms of deficiency visually resemble chlorosis: young leaves begin to yellow prematurely, their tips may wither, and overall plant development slows down significantly. In severe cases, leaf tip necrosis and delayed flowering are observed.

Excessive accumulation of nickel leads to toxic effects. Plants experience oxidative stress, and the uptake of other micronutrients like iron, zinc, and copper is disrupted, causing secondary deficiencies.

Nickel toxicity manifests as bleaching of the leaf blade, the appearance of brown spots, and deformation of the root system. Excess nickel content is often associated with anthropogenic soil contamination from industrial emissions.

In agronomic practice, chelated forms of nickel or sulfate compounds within complex micronutrient fertilizers are most commonly used. Application rates are extremely low, typically ranging from 50 to 100 grams of active ingredient per hectare.

Application is performed primarily via foliar feeding. This allows for rapid correction of deficiencies upon the first symptoms of chlorosis, as nickel is highly mobile within plant tissues.

Treatment timing depends on the growth stage of the crop. It is recommended to perform applications during periods of active growth and generative organ formation, when nitrogen metabolism demand is at its peak.

For legume crops, seed treatment with nickel solutions is justified. This promotes better development of nitrogen-fixing bacteria and increases the efficiency of atmospheric nitrogen assimilation during early growth stages.

The main limitation when working with nickel is the high risk of phytotoxicity. Exceeding recommended doses can lead to plant death or a sharp decline in yield due to disrupted cellular respiration.

Careful monitoring of soil pH is required. In acidic soils, the mobility and toxicity of nickel increase sharply; therefore, on such sites, the application of fertilizers containing this element should be strictly avoided.