Comparing activated charcoal and biochar for carbon-seeding in grass seed production

Perennial ryegrass (Lolium perenne L. ssp. perenne) seed production fields in western Oregon are often established using carbon-seeding, which consists of applying a band of activated charcoal (AC) over the seed row at the time of sowing. A preemergent herbicide is then broadcast applied to the field prior to rainfall or irrigation. In the seed row, the herbicide that encounters AC is absorbed, which allows the seed to germinate and establish. Biochar has similar characteristics to AC and is a potential alternative for carbon-seeding. Conifer-based biochars are produced in western Oregon, use less energy to make, and are less expensive than AC, providing potential benefits to stakeholders. To compare the seed row protection effects of conifer-based biochar to AC, we tested seven herbicide treatments: EPTC, diuron, indaziflam, rimsulfuron, pronamide, a combination of pyroxasulfone and flumioxazin, and a no herbicide check in a field study repeated four times in western Oregon. Results suggest that perennial ryegrass establishment was equivalent when either biochar or AC were used in combination with diuron, rimsulfuron, pronamide, and a combination of pyroxasulfone and flumioxazin signifying that biochar could be used in place of AC for these herbicides. Perennial ryegrass establishment was greater when activated charcoal was used compared to biochar when indaziflam was used. When EPTC was used, neither AC nor biochar led to perennial ryegrass establishment that was equal to the no herbicide check plots. Findings provide data on the use of biochar for carbon-seeding and an update on crop safety expectations across multiple herbicides in this system.