Influence of Different Organic Amendments on the Leaching and Dissipation of Terbuthylazine in a Column and a Field Study

Terbuthylazine (TA) is a herbicide that has been introduced for weed control in corn cultivations as a direct replacement for atrazine. Because incorporation of different organic amendments (OAs) is a common practice in this crop, this study investigated the effects of different OAs, including urban sewage sludge, poultry compost, and corn straw on the dissipation and metabolism of TA. A column study and a field dissipation study were used. In the Column study, no residues of TA and desethyl-terbuthylazine (DETA) were detected in the leachate of amended and non-amended columns. The addition of OAs increased the persistence of TA and DETA in the upper soil layers (0-10 cm) but did not affect the mobility of TA and DETA in either experiment. Although the presence of OAs led to a significant increase in DETA production in the upper soil layers, the presence of DETA in lower depths did not significantly differ with the non-amended soil in either experiment. A gradual accumulation of DETA was evident in the soil layers amended with corn straw, whereas a rapid formation of DETA and a gradual decline thereafter was observed in the other treatments. Overall, the addition of OAs did not appear to significantly influence the mobility of TA and DETA, which did not move below the top 30 cm, thus indicating low risk for ground water contamination. In addition, the dissipation rate of TA in the field was faster than that in the column study

Influence of different organic amendments on the degradation, metabolism, and adsorption of terbuthylazine

The behavior of the herbicide terbuthulazine (TA) was studied in a clay loam soil after the addition of the addition of different organic amendments (OAs). Addition of poultry compost (PC) and urban sewage sludge (USS) retarded degradation of TA (half-life 55.5 d) compared with its degradation in nonamended soils (half-life 57.3 d). Sterilization of amended and nonamended soils resukted in a partial inhibition of TA led degradation, indicating that biotic and abiotic processes are invloved in TA degradation, indicating that biotic and abiotic processes are involved in TA degradation in soil. Degradation of TA led to the formation of desethyl-terbuthylazine, which was detected in low amounts (< 80% of the initially applied TA) in all soils. Adsorption of TA was relatively low, with K-d values ranging from 2.31 L kg(-1) in the soil amended with USS. In general, K-d values increased with increasing soil amended with USS. In general, K-d values increased with increasing soil organic carbon content. The dissolved organic matter extracted from tho OAs did not appear to interact with the pesticide or the soil surfaces, suggesting that it would not probably facilitate herbicide transport. Desorption studies indicated a slight hysteresis of TA desorption in the amended soils compared with TA desorption in the nonamended soil, which is entirely reversible. These findings might have practical implications for the environmental fate of TA in agricultural soils, where the studied OAs are commonly used

Ageing of atrazine in manure amended soils assessed by bioavailability to Pseudomonas sp. strain ADP

Animal manure is applied to agricultural land in areas of high livestock production. In the present study, we evaluated ageing of atrazine in two topsoils with and without addition of manure and in one subsoil. Ageing was assessed as the bioavailability of atrazine to the atrazine mineralizing bacteria Pseudomonas sp. strain ADP. Throughout an ageing period of 90 days bioavailability was investigated at days 1, 10, 32, 60 and 90, where ~108 cells g−1 of the ADP strain was inoculated to the 14C-atrazine exposed soil and 14CO2 was collected over 7 days as a measure of mineralized atrazine. Even though the bioavailable residue decreased in all of the three soils as time proceeded, we found that ageing occurred faster in the topsoils rich in organic carbon than in subsoil. For one topsoil rich in organic carbon content, Simmelkær, we observed a higher degree of ageing when treated with manure. Contrarily, sorption experiments showed less sorption to Simmelkær treated with manure than the untreated soil indicating that sorption processes are not the only mechanisms of ageing. The other topsoil low in organic carbon content, Ringe, showed no significant difference in ageing between the manure-treated and untreated soil. The present study illustrates that not simply the organic carbon content influences adsorption and ageing of atrazine in soil but the origin and composition of organic matter plays an important role

Application of a biosorbent to soil: a potential method for controlling water pollution by pesticides

Different strategies are now being optimized to prevent water from agricultural areas being contaminated by pesticides. The aim of this work was to optimize the adsorption of non-polar (tebuconazole, triadimenol) and polar (cymoxanil, pirimicarb) pesticides by soils after applying the biosorbent spent mushroom substrate (SMS) at different rates. The adsorption isotherms of pesticides by three soils and SMS-amended soils were obtained and the adsorption constants were calculated. The distribution coefficients (Kd) increased 1.4023.1 times (tebuconazole), 1.0823.7 times (triadimenol), 1.3142.1 times (cymoxanil), and 0.5523.8 times (pirimicarb) for soils amended with biosorbent at rates between 2 and 75 %. Increasing the SMS rates led to a constant increase in adsorption efficiency for non-polar pesticides but not for polar pesticides, due to the increase in the organic carbon (OC) content of soils as indicated by KOC values. The OC content of SMS-amended soils accounted for more than 90 % of the adsorption variability of non-polar pesticides, but it accounted for only 56.3 % for polar pesticides. The estimated adsorption of SMS-amended soils determined from the individual adsorption of soils and SMS was more consistent with real experimental values for non-polar pesticides than for polar pesticides. The results revealed the use of SMS as a tool to optimize pesticide adsorption by soils in dealing with specific contamination problems involving these compounds. © 2016, Springer-Verlag Berlin Heidelberg