The behavior of herbicides in soil under sunflower growth

Ing. Umrbek Sharipov

Doctoral thesis

Abstract:

The increasing world population demands a continually growing supply of food and food products. Because of relative lack of new areas suitable for agriculture, the performance of the existing areas is enhanced by using herbicides. Herbicides are one of the crucial factors in a worldwide increase in agricultural production and contribute effectively and profitably to weed control. The aim of this work was to evaluate the sorption, mobility and degradation process of six preemergence soil-applied herbicides and their behavior in soil under sunflower growth. The experiments were provided under the field and laboratory conditions. The field experiments were conducted at three locations of the Czech Republic (Volárna, Dobroměřice and Suchdol) in between years 2015, 2016 and 2017. The experiments were set up in same design all three locations and each plot size was (2,25 x 7 m) with three replicates containing 13 treatments including the control treatment. Treatments varied in application dose: recommended and double dose for each herbicide. There were two separate experiments carried out in laboratory: the degradation and the sorption experiment. The laboratory experiments were focused on to better understanding of sorption and degradation behavior of used herbicides in soil and to prove the results from the field experiment. We were used herbicides Racer 25 EC (250 g/L of flurochloridone), Stomp 400 SC (400 g/L of pendimethalin), Bandur (600 g/L of aclonifen), Outlook (720 g/L of dimethenamid-p), Dual Gold 960 EC (960 g/L of S-metolachlor) and Successor 600 (600 g/L of pethoxamid). The herbicide aqueous solutions were used in sorption and degradation experiments in the laboratory as well as on the field experiments. The residues concentrations of herbicide in soil extracts were determined using the HPLC-UV method. The Freundlich equation were used to describe the sorption isotherms and sorption capacity of used herbicides as follow: Pendimethalin > Aclonifen > Flurochloridone > S-Metholachlor > Pethoxamid > Dimethenamid-p and among the herbicides Pendimethalin was showed the highest sorption capacity. The degradation behavior of the herbicides was relatively different due to properties of herbicides and soils. The dissipation of average half-life of herbicides were found as follows: Pendimethalin was 17.24 -51.01 days, Aclonifen was 14.3-19.7 days, Flurochloridone was 38.3-51.5 days, S-Metholachlor was 37.01-57.6 days, Pethoxamid was 17.2-25.4 days and Dimethenamid-p was 18.8-34.4 days respectively in three soils. The main conclusions can be summarized behavior of used herbicides were different due to their water solubility, dissociation constant (pKa) and leaching potential. As mentioned in the hypothesis sorption and mobility of herbicides in soils were affected by soil pH, texture and soil organic matter content and quality. Despite the hypothesis was confirmed that Herbicide degradation was faster in Chernozem than in soils that are more acid.

Abstract:

The increasing world population demands a continually growing supply of food and food products. Because of relative lack of new areas suitable for agriculture, the performance of the existing areas is enhanced by using herbicides. Herbicides are one of the crucial factors in a worldwide increase in agricultural production and contribute effectively and profitably to weed control. The aim of this work was to evaluate the sorption, mobility and degradation process of six preemergence soil-applied herbicides and their behavior in soil under sunflower growth. The experiments were provided under the field and laboratory conditions. The field experiments were conducted at three locations of the Czech Republic (Volárna, Dobroměřice and Suchdol) in between years 2015, 2016 and 2017. The experiments were set up in same design all three locations and each plot size was (2,25 x 7 m) with three replicates containing 13 treatments including the control treatment. Treatments varied in application dose: recommended and double dose for each herbicide. There were two separate experiments carried out in laboratory: the degradation and the sorption experiment. The laboratory experiments were focused on to better understanding of sorption and degradation behavior of used herbicides in soil and to prove the results from the field experiment. We were used herbicides Racer 25 EC (250 g/L of flurochloridone), Stomp 400 SC (400 g/L of pendimethalin), Bandur (600 g/L of aclonifen), Outlook (720 g/L of dimethenamid-p), Dual Gold 960 EC (960 g/L of S-metolachlor) and Successor 600 (600 g/L of pethoxamid). The herbicide aqueous solutions were used in sorption and degradation experiments in the laboratory as well as on the field experiments. The residues concentrations of herbicide in soil extracts were determined using the HPLC-UV method. The Freundlich equation were used to describe the sorption isotherms and sorption capacity of used herbicides as follow: Pendimethalin > Aclonifen > Flurochloridone > S-Metholachlor > Pethoxamid > Dimethenamid-p and among the herbicides Pendimethalin was showed the highest sorption capacity.The degradation behavior of the herbicides was relatively different due to properties of herbicides and soils. The dissipation of average half-life of herbicides were found as follows: Pendimethalin was 17.24 -51.01 days, Aclonifen was 14.3-19.7 days, Flurochloridone was 38.3-51.5 days, S-Metholachlor was 37.01-57.6 days, Pethoxamid was 17.2-25.4 days and Dimethenamid-p was 18.8-34.4 days respectively in three soils. The main conclusions can be summarized behavior of used herbicides were different due to their water solubility, dissociation constant (pKa) and leaching potential. As mentioned in the hypothesis sorption and mobility of herbicides in soils were affected by soil pH, texture and soil organic matter content and quality. Despite the hypothesis was confirmed that Herbicide degradation was faster in Chernozem than in soils that are more acid.

Keywords

Degradation, Herbicide behavior, Sorption, Mobility, Herbicide half-life

Keywords

Degradation, Herbicide behavior, Sorption, Mobility, Herbicide half-life

Language used: Czech

Date on which the thesis was submitted / produced: 4. 11. 2021

Thesis defence

• Supervisor: prof. Dr. Ing. Luboš Borůvka

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Doctoral programme / field:
Agricultural Specialization / Exploitation and Conservation of Natural Resources