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Best Practices for Soybean Pigweed Management

As growers know, herbicides are part of the farming process. The Arkansas Soybean Promotion Board has invested checkoff dollars to research the impacts of herbicide and cultural practices to improve the management of resistant pigweed populations. Tom Barber, Ph.D. conducted research with four research colleagues, Dr. Bob Scott, Dr. Jason Norsworthy and Dr. Nilda Burgos, on herbicides and crop development practices to assist in pigweed management.

“These cultural practices we’re talking about today incorporated with the herbicide system is really the way we believe we need to be moving in the future,” said Barber.

Researchers looked at several factors of soybean production such as planting dates, cover crops, row spacing and crop rotation to achieve optimal results. Barber found that crop rotation enables different herbicides to be used. The research also revealed that narrow rows allow for a quicker crop canopy and can keep pigweed from being competitive in the field.

Barber and the team also investigated the concept of weed seed control. Based on an Australian idea derived from a lack of herbicide options, the Integrated Harrington Seed Destructor was invented. When using the seed destructor attached to the combine, the seed moves through the combine in the lower chaff fraction and into the cage mill, which is turning 3,100 revolutions per minute. This basically grinds the seed into powder, eliminating the germination potential. Data from the Weed Science program has shown that pigweed holds greater than 98% of seed produced with very little seed rain or shattering. Barber notes that the destructor takes advantage of one of pigweed’s few weaknesses, seed viability. Managing the weed seed bank has become a critical step in the fight against Palmer pigweed.

We are limited to two or three options for post-control in northeast Arkansas, depending on technology, and most producers manage the crop with residuals. In 2018, a lack of rain caused a failure to activate residuals, which resulted in no protection from pigweed. The lack of pigweed control in 2018 means that the seedbank for pigweed will increase substantially, and growers should have a good game plan prior to planting in 2019. Based on Barber’s research, cover crops such as cereal rye can help reduce those pigweed germination numbers, and managing pigweed is all about the numbers.

“Cover crop is an expense without immediate cash flow benefit at the end of the year,” said Barber.

This has been a disadvantage to persuading producers to use the system. However, these cultural practices have proven successful in Barber’s research and testing.

For more of Barber's documentation on pigweed management, click here. To listen on the go, click here for the podcast version of this video as well as other helpful checkoff-funded research in audio format.

To learn more about the Arkansas Soybean Promotion Board's checkoff-funded research, watch the full Field to Film: Featured Research video series here.

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