Evolution of ability of remediation heavy metal Cadmium by some of plant species and biochar in drought stress conditions

Environmental stresses such as drought, temperature, heavy metals and salinity greatly reduce plant growth and development, among non-biological stresses, drought stress is one of the environmental factors which limits crop production and reduces average yield by 50% or more (Wang et al.,2 003). Heavy metals are another environmental stress that in recent years as it has become one of the biggest problems of the agricultural sector. Due to technical and economic limitations of heavy metal removal methods, the search for new methods has received a great deal of attention and in this regard biological absorption as a new method has received special attention(Maleki and Zarasvand, 2008).

In order to Evolution Ability of Remediation Heavy Metal Cadmium by Some of Plant Species and Biochar in drought stress conditions experimental in years 2017-2018 was carried out for two years in the research farm of the Faculty of Agriculture, Islamic Azad University, Karaj Branch. The experiment was factorial in a completely randomized design with 3 replications. Experimental factors included cadmium chloride salt at four levels (control, 10 mg.kg-1, 20 mg.kg-1, 30 mg.kg-1), Biochar at three levels (control, biochar at the time of first year planting, biochar after first year harvest and at the time of second year planting), 3 crop species (clover, alfalfa, canola) and drought stress (control, 40% available moisture discharge based on gypsum block, 60% available moisture discharge based on gypsum block). One month before planting the soil was contaminated with cadmium chloride at specific levels in the experiment then biochar treatment was added to the soil of the desired pots. After cultivating crops and sufficient vegetative growth shoot and root specimens were carefully removed from the soil of the pots and after washing and drying according to the protocol in this experiment extracts were taken for reading in an atomic absorption apparatus. For analyze the measured data, Mean and Bartlett comparison were performed using MSTATC, SAS and Excel software.

The results of analysis of variance showed that Triple interactions of cadmium, crop species, drought stress for all studied traits(Dry weight of shoots, dry weight of roots, amount of cadmium in shoots, amount of cadmium in roots, measurement of metal element, accumulation coefficient, extraction coefficient) It became significant with a one percent error probability. The results also showed that the triple interactions of cadmium, crop species, biochar only for traits Translocation factor, Accumulation factor, Enrichment cofficient became significant with a probability level of one percent. And for other traits, this triple interaction was not significant. The results of mean comparison showed that the highest mean amount of cadmium in the shoot(2.68 mg.kg-1) And roots(1.78 mg.kg-1) Related to canola treatment at the level of 30 ppm cadmium And under drought stress conditions, 60% of available moisture discharge was based on gypsum block. Most average Translocation factor related to the triple interactions of cadmium, crop species, biochar related to treatment Canola cadmium at the level of 20 ppm and biochar at the time of crop cultivation in the first year(a3b3c2) with average (3.73) and the lowest was related to cadmium control treatments (a1b1c1) with mean (0.1). The most common triple interactions of cadmium, crop species, drought stress are also related treatment of cadmium Canola at 20 ppm level without drought stress (a3b3d1) (3.98) and the lowest mean was related to cadmium control treatment (a1b1d1) with mean (0.1). Most average Accumulation factor corresponding to the triple interactions of cadmium, crop species, biochar related to the treatment of cadmium Canola at the level of 30 ppm and biochar at the time of crop cultivation in the first year(a4b3c2) with average (70.137) and the lowest was related to cadmium control treatments (a1b1c1) with mean (0.0044). Most of the triple interactions of cadmium, crop species, drought stress also related to cadmium Canola treatment at 20 ppm level without drought stress (a3b3d1) (148.87) and the lowest mean was related to cadmium control treatment (a1b1d1) with mean (0.0043). The highest mean of triple interactions of cadmium, crop species, biochar for Enrichment cofficient related to the treatment of cadmium Canola at the level of 30 ppm and without biochar in the first year (a4b3c1) with a mean (0.182) and the lowest was related to cadmium control treatments (a1b1c1) with mean (0.0117).

Most of the triple interactions of cadmium, crop species, drought stress are also related Treatment of cadmium Canola at 30 ppm level and drought stress 60% available moisture discharge based on gypsum block (a4b3d3) (0.180) the lowest mean was related to cadmium control treatment (a1b1d1) with mean (0.0011). The results of this study showed that Canola had a higher uptake and transport of cadmium metal than clover and alfalfa.