Particle analyser accurately counts weed seeds

A team of researchers at the University of Arkansas, Auburn University and North Carolina State University set out to see if a piece of technology, called a computerised particle analyser, can be used to count weed seeds. Their results are promising and show the analyser accurately counts seeds.

Matthew Bertucci, a scientist at Arkansas, says seed counting is a tiring yet important fact of life in their research.

Monitoring weed seed production

“Many weed control strategies or studies evaluate the ability of an herbicide to kill weeds and elevate crop yields,” he explains. “However, weeds that have been stunted, but not killed, may still produce viable seed that can contribute to weed populations in later years. Monitoring weed seed production then becomes important to evaluating weed control efforts.”

The group focused on the seeds from one weed, called Palmer amaranth. It’s a summer annual weed especially troubling for row and vegetable crops. While native to the southwestern United States, it has spread from coast to coast in the U.S..

Hand counting

These seeds have historically been counted by tediously hand counting a specific amount. Researchers then used that information to estimate larger quantities of seed.

To accurately hand count and double check seed numbers for this research, Bertucci and his team counted 5 seeds at a time and placed them in groups on graph paper.

While image analysis methods like the computerised particle analyser are out there, there had not been scientific proof of accuracy. Many researchers still use hand counting methods. Bertucci wanted to test and report if this imaging technology is accurate.

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When seeds are hand counted, they are grouped on graph paper so they are easier to total. Hand counting can be a tedious process. – Photo: Matthew Bertucci

“Seed production is an important part of weed control,” he says. “But there are few papers that consider weed seed production as part of a successful weed control strategy. It was my hope that by reporting on an automated seed counting alternative, more researchers might be willing to measure seed production when evaluating weed control.”

Fast-moving conveyor belt

The computerised particle analyser is a table-top lab instrument. It has a long, fast-moving conveyor belt that sends the seeds across a camera. As the seeds are pushed past the light source of the camera, they cast a shadow that is recorded and counted. The camera takes many images per second. Special software analyses the images to distinguish between seeds and non-seed material for counting.

2,000 to 2,500 seeds in 14 seconds

About 2,000 to 2,500 seeds can be hand-counted and checked in half an hour. However, the computerised method can count that same amount in roughly 14 seconds. Accounting for the time to load samples and clean the instrument, it can take just 3 minutes from start to finish.

Researchers think this technology can be used for other kinds of seeds. But, they would have to fine-tune software for each weed species based on their characteristics like size and weight.