Accumulation of trace metals and their bio-availability in soils is likely to have for reacting consequences on soil health as well as growth, yield and quality of crops. To assess the extent of trace metal contamination, soil and plant samples were collected from farmers fields around Patratu Thermal Power Station, Patratu, Kathara and Gobindpur Project CCL, Bokaro and waste disposal site, Jamshedpur. Analysis of soil pH, electrical conductivity and organic carbon content revealed that soils collected from Patratu were moderately acidic in soil reaction. Soil reaction in case of Bokaro and Jamshedpur ranged from acidic to neutral or alkaline. The electrical conductivity was within the safe limit, while the organic carbon content was medium to high. The soils were low in available N and P, while low to medium in available K status. Available micronutrients were above the critical value. DTPA-Cd was detected in 50 per cent soil samples of Patratu, 45 per cent of Bokaro and 80 per cent of Jamshedpur. All soil samples from Patratu and nearly 50 per cent samples of Bokaro and Jamshedpur contained high DTPA extractable Pb, Ni and Co. The mean value of total Cd, Pb, Ni and Co in soils were 7.76, 40.41, 238.95 and 109.27 mg kg-1 in Patratu, 8.70, 158.60, 242.45 and 218.40 mg kg-1 in soils of Bokaro and 17.50, 126.40, 143.05 and 333.10 mg kg-1 in soils of Jamshedpur. Increasing trend in soil pH with depth was observed while EC, OC, available N, P, K, micronutrients, Pb and Ni decreased with depth in each pedon. High Cd content in subsurface horizon compared to surface horizon was noticed in all pedons. Total trace metal content in soil profile collected from Patratu, Bokaro and Jamshedpur indicated that surface horizon contained comparatively high Zn and Cu, however, no definite trend for Mn and Fe was noticed. Higher Cd and Ni were recorded in soils of Jamshedpur while higher Pb and Co in soils were detected in Patratu. The plant samples collected from farmers field of Patratu had Cd ranging from traces to 34.50 mg kg-1 (guava leaves), Pb from traces to 11.45 mg kg-1 (palash leaves), Ni from 4.20 (maize and akwan leaves) to 36.00 mg kg-1 (palash leaves) and Co from traces to 39.85 mg kg-1 (palash leaves). Vegetable crops contained higher amount of trace metals particularly Cd, Pb, Ni and Co, which were nearer or above the tolerance level. Cadmium content of 75 per cent plant samples, Pb content of 58 per cent samples and Co content of all samples found to be above the MTL (Cd – 3, Pb – 10, Ni – 50 and Co – 5 mg kg-1).
Farmers’ field trial was conducted at Patratu (Ramgarh) to study the effect of lime, compost, plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi for remediation of high trace metal levels in mustard-maize cropping system. Results revealed that inoculation with Glomus mossae + vermicompost @ 2.5 t ha-1 significantly increased the grain yield of mustard (1.26 t ha-1), maize (6.72 t ha-1) and system (9.65 t ha-1) and the extent was 10, 25 and 20 per cent, respectively as compared to control. Inoculation of Pseudomonas striata + vermicompost @ 2.5 t ha-1 recorded significantly higher N, P and K uptake by mustard and maize. Inoculation with G. mossae, P. striata and A. chroococcum increased Zn concentration to the extent 13 to 32, 10 to 24 and 9 to 24 per cent, respectively over control. Copper, manganese and iron uptake followed almost similar trend as that of Zn. Microbial inoculants with or without vermicompost increased the trace metal removal, however, vermicompost alone decreased the removal. Vermicompost, lime and lime + vermicompost significantly reduced the total Cd uptake by mustard and maize. Inoculation with Glomus mossae resulted in elevated level of Cd in mustard and maize plants. Similar observations were recorded in case of Pb and Ni uptake. Estimation of bio accumulation factors (BAFs) indicates that inoculation of Glomus mossae alone resulted in significantly high BAFs value for all trace metals. It was observed that microbial inoculations reduced the total Zn, Cu, Mn and Fe content in soil. However, available micronutrients were significantly reduced by microbial inoculation and amendments. Total trace metal content in soil was significantly reduced by microbial inoculation alone or that in combination with vermicompost. However, DTPA-extractable trace metals decreased with addition of amendments as well as inoculation of microbes. Glomus mossae was most effective in remediating the trace metals under this study, the total metal content reduced effectively by their inoculation alone while inoculation along with vermicompost resulted in reducing the DTPA-extractable fraction, more effectively. The extent of reduction in total Cd, Pb, Ni and Co after harvest of both crops was 6 to 26, 5 to 12, 6 to 15 and 1 to 4 per cent, respectively over control. However, the corresponding values observed for DTPA extractable Cd, Pb, Ni and Co was 53 to 65, 20 to 32, 24 to 34 and 18 to 30 per cent over control in microbial inoculation and 46 to 47, 14 to 17, 9 to 13 and 11 to 19 per cent in case of amendments.