Home » Study examines how well-timed cover crops can suppress weeds in California orchards

Study examines how well-timed cover crops can suppress weeds in California orchards

Experiments show a variety of cover crop management programs can produce weed-suppressing cover crops.

California’s commercial orchards are home to nearly 2.5 million acres of almonds, walnuts, stone fruit and similar crops. Growers focus their most intense weed management efforts on establishing a clear crop row so that weeds won’t interfere with irrigation lines, compete with crops for water, or impede the use of sweepers and other harvesting equipment.

Any cover crops used to suppress weeds are typically grown in orchard alleyways during the rainy winter season to replace resident vegetation. A new open access study featured in the journal Weed Science, though, points to the benefit of growing cover crops concurrently with the cash crop to reduce the impact of weeds.

Emex australis seeds have dimorphic morphology. Aerial seeds that form at the leaf axils along the stems (left) have radial symmetry and subterranean seeds that form on the lower section of the crown of the plant (right) have bilateral symmetry and shorter spines. Image: Dr. Catherine Borger.

Researchers at the University of California, Davis designed two experiments – one to evaluate the impact of cover crop management intensification in walnuts, and another to evaluate multispecies cover crop mixes and planting dates in almonds.

The cover crops in the study were found to flourish under a variety of management factors. They were most abundant, though, when planted early in the growing season when adequate moisture was available.

“The uniformity in their germination results in a predictable plant cover that enhances biodiversity and promotes favorable orchard floor conditions for crop harvest,” says Steven Haring, lead researcher for the study. 

In their article Haring and Hansen write: “Such vegetation management programs allow some plant growth on the orchard floor but result in predictable plant cover and favorable orchard floor conditions for nut harvest. Orchard cover crops flourished under a variety of management programs but were most abundant with timely planting and adequate moisture during establishment. We worked in orchards that had not previously been managed with cover cropping, and any effects of cover crops on weeds could compound over the life cycle of orchard, possibly mediated through processes like depletion of weed seedbanks or weed community filtering.”


Haring, S.C. and Hanson, B.D. (2022) “Agronomic cover crop management supports weed suppression and competition in California orchards,” Weed Science, 70(5), pp. 595–602. https://doi.org/10.1017/wsc.2022.48

Dale Maylea

Dale Maylea was a system for adding value to press releases. Then he was a manual algorithm for blogging any papers that Alun Salt thinks are interesting. Now he's an AI-assisted pen name. The idea being telling people about an interesting paper NOW beats telling people about an interesting paper at some time in the future, when there's time to sit down and take things slowly. We use the pen name to keep track of what is being written and how. You can read more about our relationship with AI.

Read this in your language

The Week in Botany

On Monday mornings we send out a newsletter of the links that have been catching the attention of our readers on Twitter and beyond. You can sign up to receive it below.

@BotanyOne on Mastodon

Loading Mastodon feed...