Effect of biochar and vermicompost on the absorb of nickel metal from soil by cherry tomato (Solanum lycopersicum var. cerasiforme)

Soil is one of the most important components of the ecosystem and environment for storing nutrients and performing biological, physical, and chemical processes and activities. Earth may be infected by the accumulation of heavy elements. These metals are ubiquitous, highly persistent, and non-biodegradable. The concentration of heavy metals increases due to the natural weathering of rocks, the disposal of waste, and the use of fertilizers, pesticides, and industrial effluent. It includes nickel, which is released by car brake abrasion, vehicle corrosion (especially the car oil pump), and electronic wastes in the urban environment and its accumulation in the body causes kidney complications, lung damage, high blood pressure, and it became vascular diseases. Nickel has no toxic effect on the plant at low concentrations and acts as a micronutrient, but in high concentrations, it reduces the growth and appearance of toxic symptoms in the plants. In agricultural fields, chemical fertilizers are used to increase the production of agricultural products, which despite their benefits, their excessive use reduces crop quality and the entry of toxic pollutants into the soil. In this context, organcic amendments such as biochar and vermicompost could be useful to sustainably maintain or increase soil organic matter, preserving and improving soil fertility and crop yield. Biochar is a carbon-rich material obtained from the thermochemical conversion of biomass in an oxygen-limited environment. Biochar has been described as a possible tool for soil fertility improvement, potential toxic element adsorption, and climate change mitigation. Vermicompost is considered as a high-nutrientbiofertilizer with diverse microbial communities. It plays a major role in improving the growth and yield of different field crops, vegetables, flowers, and fruit crops. Vermicomposting is the process of conversion of organic wastes into finely degraded peat-like substances using earthworms. It is an alternative method for waste management through which vermicompost is produced with a relatively high nutrient content than compost and manures. Therefore, this study aimed to investigate the effect of biochar and vermicompost on an accumulation of nickel metal in soil and tomato fruit.

Materials and Methods :

For this purpose, the seeds were caught from a greenhouse in the south of Tehran, and the pots were filled with 3 kg of soil derived from the same place. This soil was mixed well before being placed in the pots. The test was performed as a factorial experiment in a randomized complete block design in which nickel nitrate was applied to the soil with 6 different concentrations (75 ppm nickel nitrate with 10% biochar, 150 ppm nickel nitrate with 10% biochar, 75 ppm nickel nitrate with 5% biochar, 150 ppm nickel nitrate with 5% biochar, 75 ppm nickel nitrate and 150 ppm nickel nitrate), and compared with pots that were only hydrated with tap water (control). All measurements were taken with three independent replicates for metal concentration. Pots were placed outdoors with tap water irrigation (five times a week) and two days a week (Monday and Friday) with nickel nitrate for 4 months. Then the concentration of nickel in the shoot (fruit), the nickel concentration in the soil, and the wet and dry weight of the fruit were measured. The bioconcentration factor (BCF) was also calculated using the ratio of total nickel concentration in fruit to the soil. Based on this, plants that have a bioconcentration factor of more than once, especially in their shoots, are suitable for metal extracting from the soil and translocating it to the fruit.

In general conclusion, it can be stated that planting cherry tomatoes in nickel containing soil or irrigation with municipal and industrial wastewater containing nickel should be accompanied by more considerations. Also, if biochar or vermicompost is used in the soil of cherry tomato pots, nickel can be extracted from the soil with a bioconcentration coefficient