Subsurface tillage implements, such as sweeps, are commonly used for postharvest control of Russian thistle. A sweep will kill small thistle plants and typically leaves about 85 percent of the crop residue on the soil surface. However, if tillage is delayed, or there is a moderate to heavy Russian thistle infestation, a disk is often required to chop the large amount of thistle residue that could otherwise interfere with later operations. Disking commonly buries about 40 percent more residue than sweeps, consequently reducing soil protection. Wind and water erosion, during the following summer fallow season and subsequent wheat crop, can be severe in these low rainfall areas.
Rough tillage provides only temporary erosion control in the absence of surface residue.
Postharvest chemical control of weeds can potentially reduce soil and water loss by eliminating postharvest tillage for weed control. This would allow standing stubble to remain overwinter to trap additional water as snow, reduce evaporation loss and soil freezing. In this study, Young and Gealy found that chlorsulfuron plus surfactant effectively controlled Russian thistle shortly after harvest and could eliminate a primary fall tillage operation. Without surfactant, control was reduced to 35 percent. Russian thistle was in the flowering stage with plants 10 to 12 inches tall.