PDF Article authored by: SaskCanola, SaskPulse and Sask Wheat

Herbicide carryover becomes a concern after dry conditions because soil moisture largely dictates the rate of soil residual herbicide breakdown due to its influence on two of the major degradation mechanisms: microbial activity and chemical hydrolysis. 

Although soil parameters such as pH and organic matter can influence degradation pathways, soil moisture is often the dominant factor. Soil microbes are most active in moist soils (50-100% field capacity), so a decrease in microbial activity in response to dry soil conditions reduces the amount of herbicide degradation that would typically be expected in the same time frame. Degradation through hydrolysis is also highly influenced by soil moisture as water breaks down herbicides by dividing the larger molecules into smaller, less active pieces. Read More