Nickel content in field crop seeds and agricultural soil in Central Serbia

Nickel (Ni) is an essential nutrient for animals and it has an important role in many physiological and biochemical processes in higher plants. At the same time, it belongs to the group of potentially toxic elements (PTEs). The aim of this study is to determine Ni concentrations in the soil-plant relationships between the main crops and agricultural land in Central Serbia. A total of 71 bulked soil samples are taken from the topsoil at the depth of 0-30 cm in an area belonging to 6 statistical districts of Central Serbia. A total of 71 seed samples are collected during harvest as an average sample of seed from each observed plot, of which 26 are corn, 19 sunflower, 17 wheat, and 9 soybean samples. Analysis of the collected samples includs the main soil parameters and Ni total and available concentrations in soil, as well as Ni total concentration in seeds. The median value of total Ni concentration in soil is 44.8 mg kg-1, close to MAC. The median nickel concentration in wheat and corn seeds is 0.5 mg kg-1, while soybean and sunflower seeds have higher median Ni content of 8.40 and 10.26 mg kg-1, respectively. Bioaccumulation factors in seeds (BAF) in the present study ranges from 0.013 (corn) to 0.256 (soybean). According to statistically significant differences, all crops have equal total NiT concentration in soil, while the available NiA concentration differs in soils under corn and sunflower cultivars. Based on Ni concentration in seed and BAF, two groups are distinguished − the group of soybeans and sunflowers with higher Ni content and the group of wheat and corn with lower Ni content in seed. The obtained differences confirm that plant species have a significant role in the bio­accumulation of Ni. The determined BAF parameter is in a statistically significant negative correlation with the total Ni content in soil in all observed crops except maize. However, the BAF parameter for maize alone is in a statistically significant negative correlation with the readily available Ni concentration in the soil. The obtained correlations indicate that higher Ni concentration in soil causes lower Ni concentration in seeds, which might be due to the activation of plant defense mechanism to preserve the reproductive organs ‒ seeds ‒ from harmful effects. Based on the obtained results, Ni concentration in seeds of the main field crops in Central Serbia is safe for feed and food usage. Increased content of Ni found in agricultural soils in Central Serbia requires constant monitoring for maintaining sustainable agriculture production.