The effect of Brassica napus, wheat and their composition biochar on nitrate adsorption and leaching from soil

Knowing the factors affecting the movement of water and salts in the soil profile and the use of new modifiers such as biodegradable can help to manage the proper management of nitrate leaching from the root zone and prevent the pollution of groundwater. Biochar is produced from pyrolysis of various biomasses under anaerobic conditions (or low oxygen conditions). The adsorption capacity depends on its physical and chemical properties, which is influenced by various factors such as raw material, particle size, pyrolysis temperature, temperature variation rate and temperature keeping time.

In this research, the straw of the wheat and brassica napus have grinded and after its drying, by using a furnace for 4 hours at 600 ° C, wheat and napus biochar have prepared. The treatments test included the control (soil), soil +wheat biochar 2% , soil +wheat biochar 4%, soil + Brassica napus biochar 2% , soil + Brassica napus biochar 4%. Columns with the height of 10 and 20 cm and a diameter of 160 mm have prepared, and a mixture of biochars (2% ,4%) and soil have poured into the soils columns. In order to leaching, before experiments, 10 pore volume of distilled water has poured into each of the columns. In the first day, one pore volume of water, distilled water has poured into each of the columns. The second and third days one pore volume of nitrate solution at concentrations of 20, 50 and 100 mg/L, and on days 4, 5, 6, and 7 a distilled water pore volume have added to each columns. Then the solution was filtered using paper and the concentration of nitrate was measured with a spectrophotometer to determine the amount of leached and absorbed nitrate.

The results showed that the addition of biochar to soil on both levels, especially the combinational biochar, caused a significant decrease in nitrate leaching relative to the control in all days. In general, nitrate leaching in biochar 4% less than control and biochar 2%. Also, at a height of 20 cm, the nitrate leaching rate decreased from the soil column.

Regarding the results, the use of untreated combination of brassica napus and wheat biochar resulted in lower nitrate leaching from the soil.