Influence of organic carbon on reductive dechlorination of thiobencarb in California rice field soils

Abstract

The herbicide thiobencarb is suspected of causing delayed phytotoxicity syndrome (DPS) in rice plants. While the ultimate agent appears to be its dechlorinated product (deschlorothiobencarb), the influence of organic carbon on the formation of deschlorothiobencarb in California rice field soils has not been investigated. Thus, two different soils were compared for their ability to reductively dechlorinate thiobencarb with carbon augmentation: one from the eastern Sacramento Valley, which has historically displayed DPS, and one from the western Sacramento Valley, which has not. Rice straw was homogenized into samples of each soil to produce 0, 0.33 or 2% organic carbon augmentation. During 90-days of anoxic incubation, substantial deschlorothiobencarb production was measured in both soil types. However, only the thiobencarb degradation rate in the eastern valley soil was positively correlated with carbon content. Thus, other characteristics of DPS-resistant soils may limit deschlorothiobencarb formation.

The behavior of clomazone in the soil environment

“…Soils were randomly collected from a 0–10 cm depth at all sites, transported on ice in plastic bags, preserved at 4 °C in the laboratory, air dried, ground and sieved (100 µm) and stored in sealed plastic bags until use. Properties were characterized by the Division of Agriculture and Natural Resources Analytical Laboratory at UCD27 (Table 1).…”

Partitioning of etofenprox under simulated California rice-growing conditions

“…Soils (several kg) were collected from two separate rice fields in the Sacramento Valley, California. The analytical methods for processing the soils can be found in Schmelzer et al 7 or on the UC Division of Agriculture and Natural Resources (ANR) website (http://danranlab.ucdavis.edu). Briefly, soil samples (0–10 cm) were collected via random collection from each field, air dried, ground to pass through a sieve (2 mm), further ground to a powder for sorption isotherms and then stored at room temperature until used.…”

Influence of Phosphate and Copper on Reductive Dechlorination of Thiobencarb in California Rice Field Soils

“…A number of physical-chemical properties for B and M soils were characterized by the Agriculture and Natural Resources (ANR) Analytical Laboratory at UC Davis; both the methods and results are provided in Table 1. A detailed description of the methods can be found in Schmelzer et al (14).…”