The most effective chemical treatment method to remediate heavy metal contaminated soil in agricultural lands is a combination of immobilization and phytoextraction techniques. This approach involves the use of chemical amendments to reduce the bioavailability of heavy metals in the soil, followed by the cultivation of hyperaccumulator plants to extract the metals from the soil.1. Immobilization: This technique involves the addition of chemical amendments to the soil to reduce the bioavailability and mobility of heavy metals. Commonly used amendments include: a. Lime: The addition of lime increases soil pH, which reduces the solubility of heavy metals, making them less available for plant uptake. b. Phosphates: Phosphate compounds, such as rock phosphate or bone meal, can form insoluble complexes with heavy metals, reducing their bioavailability. c. Biochar: Biochar is a carbon-rich material produced by pyrolysis of biomass. It has a high surface area and can adsorb heavy metals, reducing their mobility and bioavailability in the soil.2. Phytoextraction: This technique involves the cultivation of hyperaccumulator plants that can uptake and tolerate high concentrations of heavy metals. These plants can be harvested and removed from the site, effectively extracting the metals from the soil. Some examples of hyperaccumulator plants include: a. Brassica juncea Indian mustard : Effective for extracting lead, cadmium, and zinc. b. Thlaspi caerulescens Alpine pennycress : Effective for extracting zinc and cadmium. c. Helianthus annuus Sunflower : Effective for extracting lead, cadmium, and arsenic.Potential long-term impacts of these methods on soil health and crop productivity:1. Positive impacts: a. Reduction in heavy metal concentrations: The combined approach of immobilization and phytoextraction can effectively reduce heavy metal concentrations in the soil, making it safer for crop cultivation. b. Improved soil health: The use of amendments such as lime, phosphates, and biochar can improve soil health by increasing pH, nutrient availability, and organic matter content.2. Negative impacts: a. Disturbance of soil structure: The addition of chemical amendments and the cultivation of hyperaccumulator plants may disturb the soil structure, which could affect water infiltration, aeration, and root growth. b. Potential for recontamination: If the source of heavy metal contamination is not addressed, there is a risk of recontamination in the future. c. Disposal of contaminated plant biomass: The harvested hyperaccumulator plants contain high concentrations of heavy metals and must be disposed of properly to prevent further environmental contamination.Overall, the combined approach of immobilization and phytoextraction can be an effective method for remediating heavy metal-contaminated soil in agricultural lands. However, it is essential to monitor the long-term effects on soil health and crop productivity and to address the source of contamination to prevent recontamination.