Controlling herbicide-resistant (HR) Palmer amaranth and Kochia has historically been challenging for soybean producers. There are concerns with new herbicide-tolerant soybeans that although initially they may provide better control of these resistant weed species, however, long term we may put additional selection pressure on these weed species, which may allow for more resistant populations in the future. Other weed control strategies, that are not solely reliant on chemical weed control, need to be evaluated to develop integrated weed management programs. One of the most effective methods of weed control is the use of cultural control practices. This study will focus on the use of cultural control practices that would be easy to implement for soybean production.
It is well documented in research literature that if you increase plant-to-plant within crop competition there will be a reduction in undesirable weeds. To increase plant-to-plant competition in soybean, a producer can either increase seeding rates to increase competition in row or to decrease row spacing so that you have increased competition across the row. These types of studies have been done in traditional soybean production areas; however, they have not been done in western Kansas (west of Salina), under dryland environments.
Another weed control strategy is altering planting dates to give the crop a competitive advantage over weeds. Traditionally, soybeans are planted in May while double crop soybeans are planted in June. Delaying planting so that an extra flush of weeds can be controlled prior to planting soybean could help give soybeans a competitive advantage over those weed species. Research on evaluating soybean planting timing in western Kansas is lacking under dryland environments.
Historically, western Kansas has not been planted with near the acres of soybeans compared to the rest of the state, but there have been more acres planted in recent years. With better advancements in improved soybean genetics, we fully expect soybean production to increase in this region. Therefore, research-based information is needed on evaluating seeding rates, row spacing, and planting dates as components of integrated weed management (IWM) for the future success of those producers.