Narrow Rows Aid in Velvetleaf Control

Narrow Rows Aid in Velvetleaf Control

May 16, 2008

Velvetleaf, also known as button-weed, is an important annual weed in row crops throughout the Midwest. Its fast growth rate allows it to compete with crops for growth limiting resources such as light, nutrients and water. Velvetleaf competitiveness, however, can be reduced by modifying cultural practices, including planting crop in narrow rows.

Narrow row spacing allows the crop canopy to close earlier than in wide rows, resulting in more shade where weeds grow between the rows. Other factors, such as the time of velvetleaf emergence relative to crop emergence, also can influence the outcome of crop and weed competition. It is logical to expect that later emerging weeds will be less competitive than those emerging with the crop. This knowledge of weed relative emergence can be used when making management decisions.Field studies were conducted in eastern Nebraska at two locations in 2002 and 2003 to determine how soybean row spacing and relative time of weed emergence would affect velvetleaf and soybean growth and competition. This study was also a Masters project for Shawn Hock.

Soybean was planted in 7.5- and 30-inch rows. Velvetleaf was hand planted at soybean planting (VP), emergence (VE), and 1st trifoliate (V1) stage. Observations were made throughout the growing season to determine the effects of row spacing and relative emergence on growth and development of both the crop and weed.

The results from this study showed that velvetleaf produced much less dry matter and had about 60% less leaf area in narrow rows than in wide rows. By producing less dry matter and leaf area the weed takes fewer resources from the crop. Velvetleaf emerging at the cotyledon stage (VC) of soybean produced 65% more dry matter than velvetleaf that emerged at the V1 (1st trifoliate) crop stage.

Soybean yields were higher in the narrow rows, and when velvetleaf emerged later in the season. Soybean grown in 7.5-inch rows yielded four bushels per acre more than soybeans in 30-inch rows. Soybean yields were also reduced by 47%, 38%, and 15% when grown with velvetleaf emerging at the VC, V1, and V3 soybean stages, respectively.

Practical implication of this study is that planting narrow row soybeans will increase the crop competitiveness against weeds, including velvetleaf. Also, an early season field scouting of weed emergence patterns relative to the crop growth stage can help determine management strategies. For example, earlier emerging weeds will require earlier weed removal. This study was partially funded by a grant from the North Central Regional Weed Science grant.

Stevan Knezevic
Extension Weeds Specialist
Haskell Ag Lab, Concord, Northeast REC