Field experiments in peanut (Arachis hypogaea L.) soil ecosystem were conducted during the summer seasons (February-June) of the year 2013 and 2014 in black clay soil treated with tebuconazole at field rate (FR), 2-times FR (2FR) and 10-times FR (10FR) as foliar spray to determine the impact of tebuconazole on soil microbial properties and enzymatic activities. Tebuconazole application at FR and 2FR resulted in a short-lived and transitory toxic effect on soil microbial properties and enzymatic activities. The duration of this disturbance was slightly longer at 10FR. Incorporation of tebuconazole in soil resulted in stimulating the soil microbial activity as evidenced by increased ammonification and nitrification rates and increased soil microbial biomass at later stage. However, it was more toxic to soil ergosterol which is the indicator of the presence of viable fungi. Soil enzymatic activities like fluorescein diacetate-hydrolyzing activity, urease, phosphatase and aryl sulfatase are either unaffected or shortly inhibited and then recovered. However, dehydrogenase and nitrate reductase activity decreased more drastically and can be used as valuable indicator to assess the impact of tebuconazole application on soil health. The results indicated that instead of single assays, a broad spectrum analysis of soil microbial and enzymatic activities gives a better insight about the impacts of pesticide on soil health. From this study, it is also concluded that the application of tebuconazole at 10FR had adverse effects on the microbial variables and the effect on long-term application should be studied further.

A field experiment was conducted to examine the degradation and impact of two post-emergence herbicides (imazethapyr and quizalofop-p-ethyl) on soil ecosystems at a half recommended rate (HRE), recommended rate (RE), and double recommended rate (DRE) during kharif peanut cultivation. Herbicides were innocuous to soil microbial activity at HRE, however, showed some significant influences at RE and DRE, and exerted temporary toxic effects on microbial biomass carbon and fluorescein diacetate hydrolyzing activity. Dehydrogenase activity also declined for a shorter period except imazethapyr application at DRE. Acid phosphatase activity was inhibited whereas alkaline phosphatase activity fluctuated between promotion and inhibition, but promotion was predominant suggesting a direct role of alkaline soil environment. Soil NH and NO nitrogen were increased by the herbicides at initial (after 7 days) and last phases (after 30 days), respectively. After an early period of inhibition, urease activity returned to the control level after 30 days. Dissipation of imazethapyr residues fitted best to bi-exponential order rate kinetics at DRE and RE, whereas it followed first-order rate kinetics at HRE. The residues of quizalofop-p-ethyl were found only up to 1 day after application suggesting its rapid conversion to active acid metabolites. Both the herbicides had transient harmful effects on most of the soil microbiological parameters.

A laboratory experiment was conducted to investigate the efficiency of chemically and thermally activated peanut husk (APNH) for removing atrazine from aqueous solutions. The prepared APNH was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Batch experiments were serially conducted to evaluate the effect of various parameters such as pH, dose of APNH, contact time, and interfering cations, anions and other agrochemicals. Freundlich and Langmuir isotherm and pseudo‐second‐order models were fitted to the equilibrium and kinetic data, respectively. Linear and nonlinear regression methods were also compared while nonlinear regression performed better for analyzing experimental data for both kinetic and isotherm analysis. This study illustrates a practical relevance in exploring the potentiality of activated peanut husk/shell to remediate water pollution by simulating the several environmental factors which can govern the real scenarios. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 348–358, 2017

A field experiment was conducted to study the dissipation kinetics of herbicides pendimethalin and oxyfluorfen in black soil of peanut field at half recommended rate (HRE), recommended rate and double recommended rate as well as to assess their effects on soil microbial parameters and enzymatic activities. In addition, their role in the transformations and availability of some plant nutrients like nitrogen transformation (through ammonification and nitrification processes) and availability of phosphorous were also studied. Incorporation of these herbicides was found to stimulate the activity of soil microbial biomass carbon, fluorescein diacetate hydrolysing activity, alkaline phosphatase and ammonification rates, while dehydrogenase activity, acid phosphatase, nitrification rate and available phosphorous was adversely affected. However, urease remains almost unchanged except for little stimulation at later stages. Dissipation of pendimethalin and oxyfluorfen followed first-order reaction kinetics with half-life (T 1/2 ) of 13.7-20.1 and 21.5-27.4 days, respectively. Residues of both herbicides persisted up to 60 days in the soil at all the doses except 45 days for pendimethalin at HRE.