A Better View of Cover Crops Could Help Weed Control

Imagine a farmer flying a drone over a rye cover crop field. An app on his smartphone quickly generates a map of the field showing where weeds are likely to appear later in the season. A month later, the farmer returns and has a drone-sprayer directly treating those areas with a herbicide mixture targeting those specific weed species. Compared to spraying the entire field, he has spent a fraction of the time and money.

A productive collaboration between North Carolina State University, Texas A&M, Iowa State University, and the USDA is on its way to making this scenario a reality. The goal is to create a mobile app that allows a grower to take a video over a cover crop – whether it be by drone, tractor-mounted smartphone, or by simply walking with a smartphone – and obtain a map showing specific places where the cover crop is sparse. This will show the grower where weeds are most likely to grow later in the season.

The purpose of the app is two-fold: to make it easier for growers to use winter cover crops for weed control, and to reduce the amount of herbicide use overall. Cover crops are often patchy in the field due to differences in soil properties such as texture, moisture, and fertility. Wherever the cover crop is underperforming (i.e. biomass is low), it is less likely to prevent weeds from germinating and growing. The app will show areas where the cover crop is thin or small and needs to be monitored for weeds later in the season. It will also help growers treat weed escapes sooner before allowing them to go to seed. Even if late-season weed escapes do not directly affect yield, allowing them to produce seed contributes to next year’s weed seed bank. In this way, growers will be able to make plans to specifically target those areas and avoid spraying the entire field. This will save growers money in herbicides, slow the rate of herbicide resistance, and help with long term weed management.

Our research team is currently developing ways to estimate cover crop biomass using video images. Using a GoPro camera, we are taking videos over various cover crop fields at different growth stages. We then use the videos to create 3-D reconstructions known as “point clouds” of the crop.

By comparing the point clouds with other data such as crop height and normalized differential vegetation index (NDVI), we can map the cover crop biomass and density anywhere in the field. This will allow us to see patches where the cover crop is sparse – similar to an elevation map – and where we are most likely to see late-season weed escapes. To see how we collect the data and create 3-D reconstructions of the cover crop, watch a video of our research process below.

Video by April Dobbs, North Carolina State University.

Precision agriculture continues to make strides in helping growers increase yields while reducing inputs. Our app will provide a powerful tool for growers to better use cover crops while reducing the time, money, and chemical inputs required for weed control. With simple and inexpensive cameras and smartphone technology, it will help create a brighter future for agriculture and the environment.

For more information on the NCSU weed science program, visit their website here: https://weedscienceprogram.wordpress.ncsu.edu/ and follow them on Facebook here: https://www.facebook.com/NCSUweeds.

For more information from GROW on using cover crops as weed control, see this webpage: https://growiwm.org/cover-crops/

Article and video by April Dobbs, NCSU Graduate Student