Persistence Behavior of Penoxsulam Herbicide in Two Different Soils.

Penoxsulam, a new post emergence herbicide is suspected to be toxic to aquatic organisms, crop plants and also to soil microbial community even at low concentrations. Laboratory studies were therefore performed to examine the persistence of, penoxsulam in two different soils at two application rates (0.5 and 1.0 µg g-1). The study revealed that the dissipation followed the first order kinetics with a half life of 3.48 and 3.57 days at 0.5 µg g-1 and 4.1 and 4.17 days at 1.0 µg g-1 fortification rate. Both microbial- and photo-degradation seemed to play a vital role in the dissipation of penoxsulam. The results of LC MS/MS revealed that one minor and five major metabolites were formed during the degradation process of the herbicide and the cleavage of sulfonamide bridge served as the major metabolic pathway.

Valorisation of phyto-biochars as slow release micronutrients and sulphur carrier for agriculture.

Slow release micronutrients and sulphur sources are required for higher use efficiency of fertilizers in agriculture. The present investigation was undertaken to examine the salt soluble, desorbed and specifically sorbed fractions of micronutrients and sulphur in nutrient enriched phyto-biochars incubated at 15, 25 and 35°C for 48 h after pyrolysis of Lantana sp., Pinus sp. needles and wheat straw at 300 and 450 °C. The highest salt soluble fractions of Zn, Cu, Fe, Mn and B were recorded with pine needle biochar pyrolyzed at 300 °C, whereas that of S with lantana biochar pyrolyzed at 300 °C. The highest desorbed contents of Zn, Cu and Mn were with pine needle biochar (300 °C) and that of B and S with wheat straw biochar (450 °C) and lantana biochar (300 °C), respectively. An increase in incubation temperature from 15 to 25 °C increased the salt soluble contents of Zn and specifically sorbed contents of Fe and B but decreased salt soluble contents of Fe and B and desorbed amount of S significantly. Further, increase in incubation temperature from 25 to 35 °C significantly decreased the salt soluble contents of all nutrients except Mn and desorbed amount of S but increased specifically sorbed amount of Fe, B and S. Considering the salt soluble and desorbed contents of nutrients in enriched phyto-biochars, especially pine needle biochar pyrolyzed at 300 °C and treated with marginal or deficient nutrients for 2 d at 15-25 °C appeared to be suitable as a slow release fertilizer.

Sorption-desorption of some transition metals, boron and sulphur in a multi-ionic system onto phyto-biochars prepared at two pyrolysis temperatures.

The sorption-desorption of transition metals, B and S onto phyto-biochars prepared from lantana, pine needles and wheat straw by pyrolysis at 300 °C and 450 °C were studied using the batch method. Their sorption-desorption onto phyto-biochars conformed to Freundlich isotherms. Phyto-biochars pyrolyzed at 450 °C had higher sorption capacity for transition metals (Zn, Cu, Fe, and Mn) but lower sorption capacity for S as compared to those pyrolyzed at 300 °C. The desorption capacity of phyto-biochars pyrolyzed at 450 °C for transition metals, B and S was also higher than that of phyto-biochars pyrolyzed at 300 °C except for S in pine needle biochar. Percent desorption of all transition metals, B and S was lower for phyto-biochars pyrolyzed at 450 °C compared to those pyrolyzed at 300 °C; however, an opposite trend was noted for Mn and S in the case of pine needle and wheat biochars, respectively. Simple correlation analysis of Freundlich model constants, desorption index and percent desorption values of transition metals, B and S with the properties of phyto-biochars and changes in Fourier transform infra-red spectra after sorption revealed that several conjunctive mechanisms such as cation exchange, complexation and co-precipitation for the sorption of transition metals, H-bonding/ligand exchange for B and H-bonding/cation bridging for S were operative in phyto-biochars. Phyto-biochars produced from plant biomass wastes by pyrolysis at 300 °C, which have been enriched with Zn, Cu, Fe, Mn, B and S may serve as a potential slow-release nutrient carrier in agriculture.

Fate of benfuracarb insecticide in mollisols and brinjal crop.

The fate of benfuracarb was studied under field conditions in brinjal fruits and soil following foliar spray application at 0.25 and 0.50 microg g(-1) by HPLC. At 0.25 microg g(-1), benfuracarb persisted up to 7 days both in soil and brinjal but at 0.50 microg g(-1), benfuracarb residues persisted up to 10 and 12 days in soil and brinjal fruits, respectively. The persistence of benfuracarb residues, both in soil and brinjal, followed first-order kinetics. The half-life values of benfuracarb in soil and brinjal fruit were found to be 3.54 and 3.90 days at 0.25 microg g(-1) and 3.75 and 4.73 days at 0.50 microg g(-1), respectively.

Sorption-desorption of fipronil in some soils, as influenced by ionic strength, pH and temperature.

BACKGROUND: The sorption-desorpion of fipronil insecticide is influenced by soil properties and variables such as pH, ionic strength, temperature, etc. A better understanding of soil properties and these variables in sorption-desorption processes by quantification of fipronil using liquid chromatography may help to optimise suitable soil management to reduce contamination of surface and groundwaters. In the present investigation, the sorption-desorption of fipronil was studied in some soils at varying concentrations, ionic strengths, temperatures and pH values, and IR specta of fipronil sorbed onto soils were studied. RESULT: The sorption of fipronil onto soils conformed to the Freundlich isotherm model. The sorption-desorption of fipronil varied with ionic strength in each of the soils. Sorption decreased but desorption increased with temperature. Sorption did not change with increasing pH, but for desorption there was no correlation. The cumulative desorption of fipronil from soil was significantly and inversely related to soil organic carbon content. IR spectra of sorbed fipronil showed the involvement of amino, nitrile, sulfone, chloro and fluoro groups and the pyrazole nucleus of the fipronil molecule. CONCLUSION: The sorption of fipronil onto soils appeared to be a physical process with the involvement of hydrogen bonding. An increase in soil organic carbon may help to reduce desorption of fipronil. High-temperature regimes are more conducive to the desorption. © 2015 Society of Chemical Industry.