Published on Wednesday, October 7, 2020
Do you face the same challenging weeds you faced 20 or 30 years ago? In the past 30 years, farmers have adopted more soil conservation practices such as no-till and shallower tillage methods. This shift in tillage practices will impact the weed species in your fields. Weeds such as marestail have a very thin seed coat, making any form of tillage detrimental. Weeds such as waterhemp are very small, making deeper tillage, such as a moldboard plow, very effective at reducing waterhemp emergence.
Deeper tillage has less of an impact on larger seeded weeds (cocklebur, morningglory, and giant ragweed) compared to smaller seeded weeds. Should we go back to deeper tillage? Not necessarily. We still need to think about soil conservation and protecting the soil. What if we have a year that invokes preventive plant or fallow ground, or a field where the seed bank has been recharged? What if we moldboard the field, burying the seed, and then return to vertical tillage the following year? Beck’s Practical Farm Research (PFR)® has set up a long-term tillage study to evaluate the impact of tillage on weed control, which in 2020, simulated the impact following a year of preventive plant or fallow ground.
When using vertical tillage (VT) followed by (fb) VT, we saw the greatest waterhemp emergence in the untreated portion of the study. Why? The same reason we put after-market closing wheels on our planter: to improve seed-to-soil contact. The VT fb VT treatment was shallow enough to allow the waterhemp to emerge and had greater seed-to-soil contact. The chisel plow that was used was not a disk chisel, so there was no mixing of the soil and weed seeds. The ridges in between the shanks had a large amount of weeds due to the lack of mixing. The moldboard had the least amount of large- and small-seeded weeds. However, if continuous moldboard tillage was used, the seeds would be brought back to the soil surface. Though deeper tillage worked the best for burying weed seeds, we must also consider soil conservation. Deeper tillage worked well as a “rescue” application but may not be the best option on a yearly basis.
The combination of a pre-emerge herbicide program with tillage can greatly increase weed control, as seen in the table at right. The number of SOAs in the pre-emerge application plus the type of tillage has an increasing influence on the number of weeds that emerged, truly showcasing the Power in the PRE™.
Author: Joe Bolte
Categories: Agronomy, Agronomy Talk