Abdur Rehim

Phytoremediation strategies for soils contaminated with heavy metals: Modifications and future perspectives

Presence of heavy metals in agricultural soils is of major environmental concern and a great threat to life on the earth. A number of human health risks are associated with heavy metals regarding their entry into food chain. Various physical, chemical and biological techniques are being used to remove heavy metals and metalloids from soils. Among them, phytoremediation is a good strategy to harvest heavy metals from soils and have been proven as an effective and economical technique. In present review, we discussed various sources and harmful effects of some important heavy metals and metalloids, traditional phytoremediation strategies, mechanisms involved in phytoremediation of these metals, limitations and some recent advances in phytoremediation approaches. Since traditional phytoremediation approach poses some limitations regarding their applications at large scale, so there is a dire need to modify this strategy using modern chemical, biological and genetic engineering tools. In view of above, the present manuscript brings both traditional and advanced phytoremediation techniques together in order to compare, understand and apply these strategies effectively to exclude heavy metals from soil keeping in view the economics and effectiveness of phytoremediation strategies.

Zinc fertilization approaches for agronomic biofortification and estimated human bioavailability of zinc in maize grain

ABSTRACT Maize (Zea mays L.) is generally low in bioavailable zinc (Zn); however, agronomic biofortification can cure human Zn deficiency. In the present experiment, Zn was applied in pots as ZnSO4 · 7H2O to maize cultivar DK-6142 as foliar spray (0.5% w/v Zn sprayed 25 days after sowing and 0.25% w/v at tasseling), surface broadcasting (16 kg Zn ha−1), subsurface banding (16 kg Zn ha−1 at the depth of 15 cm), surface broadcasting + foliar and subsurface banding + foliar in comparison to an unfertilized control. As compared to control, all treatments significantly (P ≤ 0.05) increased growth, yield and nutritional attributes in maize. Grain Zn and protein concentrations were correlated and ranged from 22.3 to 41.9 mg kg−1 and 9 to 12 %, respectively. Zinc fertilization also significantly reduced grain phytate and increased grain Zn concentration. Zinc fertilization, especially broadcasting and subsurface banding combined with foliar spray decreased grain [phytate]:[Zn] ratio to 28 and 21 and increased Zn bioavailability by trivariate model of Zn absorption to 2.04 to 2.40, respectively. Conclusively, broadcasting and subsurface banding combined with foliar spray is suitable for optimal maize yield and agronomic Zn biofortification of maize grain. This would also be helpful to optimize Zn and protein concentration in maize grain.

Efficiency of Zinc and Phosphorus Applied to Open-pollinated and Hybrid Cultivars of Maize

Improving efficiency of applied nutrients is important to produce optimum crop yields with reduced fertilizer inputs. Phosphorous (P) has antagonistic effect on zinc (Zn) uptake by plants and information on the efficiency of these each nutrients in maize cultivars are limited. This study evaluated the response of different levels of Zn (0, 9 mg kg soil) and P (0, 40 mg kg soil) on growth, nutrient uptake and their utilization efficiency in four maize cultivars differing in their growth behavior (DK–6142, P1543, Neelam and Afghoi) when grown under natural greenhouse conditions. Maize cultivars significantly differed for above given traits and among treatments, combined Zn+P application increased dry matter, nutrient uptake and their efficiency as compared with control. Agronomic, physiological and recovery efficiency of P increased in Neelam, Afghoi and DK–6142 cultivars with Zn applied and vice versa. Afghoi and DK–6142 cultivars were more responsive for agronomic, physiological and apparent Zn and P recovery efficiency than other ones. For P1543 cultivar, Zn and P physiological efficiency decreased while recovery efficiency increased, respectively with combined application of both nutrients. However, for each of the nutrients utilization efficiency, none of these were related to open pollinated or hybrid maize cultivars and rather dependent on genetic makeup for internal higher utilization efficiency. Overall, nutrient efficiency of applied Zn or P are interdependent on each other and maize cultivars had a differential response to their applications.

Effect of distillery spentwash fertigation on crop growth, yield, and accumulation of potentially toxic elements in rice

AbstractThe safe disposal of industrial effluents always remained a challenging process because of their high level of nutrients, toxic elements, and salts. A pot experiment was conducted to investigate the effects of various concentrations (5%, 10%, 15%, and 20%) of sugar industry effluent spentwash (SW) fertigated with tab water (TW), on soil properties, crop growth, physiological parameters, yield components, and accumulation of potentially toxic elements (PTEs) in rice (Oryza sativa L.) grains and straw. The results showed that soil physico-chemical properties were modified with rise in SW concentration. Application of 5% SW significantly enhanced the plant growth, and yield components. Photosynthesis rate, transpiration rate, and stomatal conductance were significantly higher under 5% SW concentration in comparison with control. However, SW concentrations of > 5% showed inhibitory effects for all growth, physiological, and yield components. Accumulation of PTEs showed increasing trend with rise in SW concentration. However, under 5% SW concentration, all the PTEs in rice grain and straw were within the permissible limits (PLs) recommended by FAO/WHO and no health hazards were detected by health risk assessment. Based on the study results, 5% SW fertigation with TW can be applied as fertilizer for enhancing the growth and productivity of rice. Graphical abstract