With that question in mind, three researchers at University of Illinois- Christopher Landau, Aaron Hager, and Martin Williams II, set to explore the combined effects of weather conditions and the level of weed control on corn yield. The results are published in a paper titled “Diminishing weed control exacerbates maize yield loss to adverse weather
”. Employing the power of machine learning and data mining techniques they modeled an expansive database of herbicide efficacy trials across 205 weather conditions in Illinois and 27 years. Machine-learning algorithms helped the researchers make sense of the large, complex dataset. They looked at crop management considerations, including planting date, hybrid choice, and planting density; percent weed control for multiple weed species; weather data at key growth stages throughout the corn life cycle; and yield. The results indicated that late-season control of all weed species was the most important predictor of corn yield loss due to weeds. Treatments with poor late season weed control of <12% resulted in the highest average corn yield loss of 50%. The lowest average yield loss was 3% in treatments with the late season weed control assessed as high as ≥94%.
These are interesting results because for a late planted crop such as corn, one would expect herbicide sprays and mechanical activities to prepare the field would destroy early weed cohorts and reduce overall competition with the crop. However, various weeds tend to germinate and emerge throughout summer. Additionally, hot and dry weather conditions tend to reduce the efficacy of post emergence herbicides. So, poor weed control coupled with resistant species could quickly result in overall poor weed control and reduce crop yields. Also, the combined effects of weed/crop competition and adverse conditions during the corn flowering and grain filling stages would tend to affect further the realized yield.
So, as more and more weeds develop herbicide resistance and weather conditions trend towards hot and dry summers, there is a need to rethink weed control practices in various crops. Diversifying weed control to include seed destruction and other techniques could reduce the overall soil weed seedbank and minimize emergence throughout the summer season.
The paper by Christopher Landau, Aaron Hager and Martin Williams II titled “Diminishing weed control exacerbates maize yield loss to adverse weather” is available online as an open access and it was used as a reference to prepare this blog.