| Fertilizers

Nickel increases soybean productivity, but requires careful dosage, study indicates

Micronutrient stimulates plant growth and improves the absorption of essential nutrients, but high doses can cause toxicity and compromise development

29.09.2024 | 09:18 (UTC -3)

Cultivar Magazine

Effect of five Ni application rates on growth parameters: a) e) shoot dry weight; b) f) root dry weight; c) g) nodule dry weight; and d) h) grain yield in soybean genotypes Gen1 (NS 8080 IPRO) and Gen2 (NS 6446 I2X). ⁎ Significant according to F-test at P < 0,05. Mean values and standard deviations were calculated from four replicates. Different letters indicate significant differences according to Fisher's least squares difference (LSD) test at P < 0,05. Gray rectangles highlight the most responsive treatments — Effect of application of five doses of Ni on growth parameters: **a) e)** dry weight of aerial part; **b) f)** dry weight of the root; c) g) dry weight of the nodule; and **d) h)** grain yield in soybean genotypes Gen1 (NS 8080 IPRO) and Gen2 (NS 6446 I2X). ⁎ Significant according to F-test at P < 0,05. Mean values and standard deviations were calculated from four replicates. Different letters indicate significant differences according to Fisher's least squares difference (LSD) test at P < 0,05. Gray rectangles highlight the most responsive treatments

The application of nickel (Ni) in agriculture has been consolidated as one of the main discoveries for improving plant cultivation, especially for leguminous crops such as soybeans. Recent studies show that Ni can act both beneficially and detrimentally for plant development, depending on the dosage used. This duality is part of a phenomenon known as hormesis: low doses of an element can stimulate growth, while high doses can inhibit development.

The research evaluated the influence of five Ni doses (0,0, 0,5, 1,0, 3,0 and 9,0 mg of Ni per kg of soil) on the ionomic profile of two soybean varieties. The objective was to understand how Ni, when introduced as a new micronutrient, impacts the dynamics of other chemical elements present in the plant-soil system. The study showed that, when added to the soil, Ni can reduce the concentration of cationic micronutrients such as manganese (Mn), iron (Fe), zinc (Zn) and copper (Cu), while increasing the concentration of macronutrients such as nitrogen (N) and magnesium (Mg). In addition, a decrease in the accumulation of aluminum (Al), an element toxic to plants, was observed.

The greatest change in the ionomic profile was observed in the leaves, followed by the grains, nodules and roots. The application of agronomic doses of Ni, i.e., in adequate quantities, proved to be beneficial for the growth and productivity of soybeans, although the results vary according to the plant genotype.

The role of nickel as a micronutrient

The role of Ni as an essential micronutrient for plants was established in the 1980s. Its main function is related to the activation of urease, an enzyme that plays a crucial role in nitrogen recycling in plants. Ni acts as a cofactor for this enzyme, allowing urea to be hydrolyzed into ammonia and carbon dioxide, preventing the toxic accumulation of urea.

However, the use of Ni in agriculture goes beyond this function. It also participates in enzymatic processes in microorganisms associated with plants, as in the case of soybeans, which have an efficient biological nitrogen fixation (BNF) process. Soybeans, which occupy a prominent position in global agricultural production, benefit from nickel fertilization, which improves the efficiency of this process, resulting in greater productivity.

Effects observed in the study

The study showed that the application of Ni to soybeans at appropriate doses generates benefits. The dose of 3,0 mg of Ni per kg of soil was the one that presented the best results, with an increase in plant growth and productivity. However, the application of higher doses, such as 9,0 mg of Ni per kg of soil, altered the ionomic profile of the plant, resulting in toxic effects and underdevelopment. This highlights the importance of adjusting the Ni dose to avoid harmful effects on the crop.

Furthermore, Ni showed a complex interaction with other essential plant nutrients. There were significant correlations between Ni and the elements N, Mn, Fe, B, Zn and Cu, indicating that nickel may control the uptake and translocation of certain nutrients, especially cationic ones. Another highlight was the antagonistic behavior of Ni towards aluminum, a potentially toxic element, suggesting that Ni may help plants resist Al accumulation in areas with excess of this metal.

Conclusions and implications for the future

The study concluded that the use of Ni at adequate doses is beneficial for soybean cultivation, increasing yield and improving nutrient absorption. However, excessive doses can cause toxicity and compromise plant development. The interaction of Ni with other essential elements should be further explored, especially in the long term, to better understand its role in plant nutrition.

Ni application may also be a promising tool to increase soybean resistance to soils with excess aluminum, a common problem in many agricultural regions. These results open new possibilities for the use of nickel as an innovative micronutrient in agriculture, but reinforce the need for careful dosage to avoid negative effects.

More information can be found at doi.org/10.1016/j.plantsci.2024.112274