Mitigating toxicity of arsenic in sunflower (Helianthus annuus L.) with phosphate rock and farmyard manure using contrasting soil textures.

Arsenic (As) immobilization in soil using inorganic/organic amendments may improve the productivity of As-contaminated soils. However, the degree of immobilization may vary depending on soil texture, phosphorus and organic matter content. A pot study was designed to investigate the effect of phosphate rock (PR) and farmyard manure (FYM) on As solubility in three soil types (sand, loam and clay), its transfer to plant parts and the resultant impact on physiology and achene yield of Helianthus annuus L. under alkaline calcareous condition. Plants were treated with As (60 and 120 mg kg^-1 soil), PR (5 and 20 g kg^-1 soil) and FYM (5 and 20% w/w) with a control. After sixteen weeks of growth period, results showed that As solubility decreased by 22.07-44.85% and 21.33-36.35% in sand, 17.55-45.80% and 30.83-45.98% in loam, while 22.81-36.89% and 20.92-42.41% in clay soils at As-60 and As-120, respectively with varied PR+FYM combinations compared to control. Integrated PR+FYM application restricted As movement from soil to plant, reducing achene As concentration by 22.22-41.26%, 26.08-43.47%, and 25.80-45.16% in sand, loam and clay soils, respectively, at As-120 compared to without PR+FYM. Thus, integrated PR+FYM application could be recommended to enhance the productivity of As-contaminated marginal lands by sunflower cultivation.