Use of organic soil conditioners to improve sunflower's phyto-stabilization in copper-contaminated soil

The presence of copper (Cu) in agricultural soils represents an increasingly serious environmental concern around the globe. In this regard, the use of organics byproducts as soil conditioners has gained much attention for restoring Cu contaminated soils; however, limited research has been available regarding the comparative effectiveness of compost (CP), rice husk (RH), rice husk induced biochar (RHB), poultry manure (PM) and animal manure (AM) when used with sunflower (Helianthus annus L.). A pot trial was arranged in a complete randomized design with five different treatments along with their three replicates each to evaluate the comparative effects of soil amendments for Cu immobilization in alkaline calcareous soil of arid region. The results showed the significant increase in soil pH in all soil conditioners treated soil. While, the slight reduction in CP amended soil was noticed by 0.1 unit over control. Though, the remaining soil conditioners exhibited the increment in soil pH over control. In addition, the profound reduction in Cu was recorded by 9%, 17.8%, 33.7% and 28.4% when CP, RH, RHB and PM were applied at 2% (w/w) respectively, over non-treated soil. This study demonstrated that the incorporation of RHB showed the prominent reduction Cu mobility into polluted soil. Moreover, all soil conditioners exhibited the prominent improvement in sunflower growth and reduced Cu absorption in sunflower shoots and roots. Hence, these soil conditioners represent an efficient strategy to transform organic wastes into valuable products like biochar and compost, promoting a circular economy approach.