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Nisha Sahu ¹, P. Raha ¹, Asha Sahu ², Udai B. Singh ¹

Affiliations
1 Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005, IN
2 Division of Soil Biology, Indian Institute of Soil Science, Nabibagh, Berasia Road, Bhopal-462 038, M. P., IN

Abstract

Acephate, dimethoate and phosphamidon are organophosphate pesticides with high toxicity and may significantly affect soil microbial activities. However, the magnitude of this effect is unclear yet. The potential harmful effect of these pesticides on soil enzyme activity was accessed in the soil collected under controlled laboratory conditions. We examined the effect of recommended (RD) and double the recommended doses (2RD) of these pesticides on the soil enzymatic activities. The incubation study was carried out at 60% of maximum water holding capacity of the soil sample at 28±2°C for a period of 42 days. Our results indicated that high acephate, dimethoate and phosphamidon doses significantly affect enzymatic activities in the soil. Our results provide the first evidence that acephate, dimethoate and phosphamidon differentially affected the soil microbial community through inhibiting fungal and bacterial populations.

Keywords

Organophosphate Pesticides, Enzyme Activities, Alluvial Soil.

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Asha Sahu ¹, S. K. Singh ¹, Nisha Sahu ², Bali Ram ³, M. C. Manna ⁴

Affiliations
1 Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi-221 005, IN
2 National Bureau of Soil Survey & Land Use Planning (ICAR), Amravati Road, Nagpur-440 033, IN
3 Department of Chemistry, Hindu University, Varanasi-221 005, IN
4 Division of Soil Biology, Indian Institute of Soil Science, Nabibagh, Berasia Road, Bhopal-462 038, IN

Abstract

Sorption isotherms have been widely used to assess the heavy metals retention characteristics of soil particles. Adsorption behaviour of cadmium (Cd) in soils is an important process which exerts a major influence on its uptake by plant ischolar_mains. Desorption behaviour of the retained metals, however, usually differ from that of adsorption, leading to a lack of coincidence in the experimentally obtained adsorption and desorption isotherms. Three soils differing in physico-chemical properties (pH 5.7 to 8.2) and varied taxonomy (Typic Ustochrepts, Typic Rhodustalfs and Entic Chromusterts), were subjected to Cd treatment at various concentrations (0, 2, 4, 8, 15, 30, 45, 75 mg Cd/L). The Cd adsorbed by each soil was calculated as the difference between the amount of Cd present in the solution initially and that remaining after equilibration. Immediately after adsorption, desorption took place using successive dilution method with five consecutive desorption steps. Both, Cd adsorption and desorption data were described by Freundlich equation. The adsorption and desorption reactions, however, did not provide the same isotherms, indicating that hysteresis occurred in Cd adsorption-desorption process. Results indicated that the adsorption capacity of the soils for Cd increased with an increase in the pH or alkalinity of the soils. The rate of adsorption was, however, found to decrease with increased pH. But no specific trend was observed in case of desorption. All the three soils used in this study followed Freundlich adsorption isotherms. The adsorption data, in general, indicated that Cd was in a fixed form at higher pH levels. The Cd adsorption was in the order of Entic Chromusterts > Typic Ustochrepts > Typic Rhodustalfs.

Keywords

Adsorption-Desorption, Cadmium, Sorption Isotherms, Soil Orders.

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Asha Sahu ¹, Nisha Sahu ²

Affiliations
1 Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221 005, IN
2 National Bureau of Soil Survey & Land Use Planning (ICAR), Amravati Road, Nagpur-440 033, IN

Abstract

Heavy metals are potentially toxic to human life and the environment. In a greenhouse pot experiment, Typic Ustochrepts soil order (alluvial soil) with pH 5.7 was used. African marigold variety Pusa Narangi was used as a test crop. The soil was artificially spiked with different cadmium (Cd) levels (0, 5, 10, 25, 50 and 100 mg kg^-1). Critical toxic concentrations of Cd resulting in 25 per cent reduction in dry matter yield were established for African marigold grown in alluvial soil. The corresponding values for non-inoculated, arbuscular mycorrhiza (Glomus moseae) and phosphorus solubilizing fungi (Aspergillus awamori) treated soils, respectively, were 28, 24 and 16 mg kg^-1 Cd applied in soil; 12, 12 and 8 mg kg^-1 AB-DTPA extractable Cd in soil; 6.4, 6.2 and 6 mg kg^-1 Cd content in plant tissues.

Keywords

African Marigold, Cadmium, Critical Toxic Concentration, Dry Matter Yield.

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