Field pennycress seed has shown promise as a source of oil for biodiesel, as well as meal to use as a biological herbicide, said Kwesi Ampong-Nyarko, research scientist with Alberta Agriculture.
Field pennycress is known to most farmers as stinkweed or french weed.
Botanically, pennycress is in the mustard family. It grows as either a summer or winter annual. Wild populations live in many disturbed habitats, from roadsides and vacant lots, to beaches.
Pennycress, listed as stinkweed, was among the five most abundant weeds in weed surveys of Alberta and Saskatchewan cropland.
Read Also
Ag in Motion speaker highlights need for biosecurity on cattle operations
Ag in Motion highlights need for biosecurity on cattle farms. Government of Saskatchewan provides checklist on what you can do to make your cattle operation more biosecure.
The commercial interest in field pennycress comes from the oil content of the seed, which ranges from 26 to 40 percent. The oil is suitable for industrial uses such as low temperature lubrication and biodiesel production.
The meal left behind after the oil extraction is high in glucosinolates.
Glucosinolates are common in the mustard family and are responsible for the sharp taste in mustard and horseradish, and the cancer-fighting properties in broccoli, brussels sprouts, cauliflower and other crucifer vegetables.
However, glucosinolates can be toxic, especially in high doses, which can be used to turn the meal into an organic bioherbicide.
Ampong-Nyarko tested the potential of the bioherbicide in greenhouse trials. Pennycress meal suppressed a variety of broad-leaved weeds such as lamb’s quarters, purslane, stinkweed, white cockle, scentless chamomile, cow cockle, dandelion, common groundsel and redroot pigweed.
It was less effective at suppressing grassy weeds.
The amount of meal needed for effective weed control is probably too high to make it an effective tool for field crops, but it has potential for use in horticultural crops.
High value vegetable and herb crops are often grown using plastic mulch for weed control. A strip of plastic is laid down, and desired plants are transplanted through holes in the plastic.
This eliminates most weeds but there can still be intense competition with weeds that emerge through the holes in the mulch.
In rhodiola test plots at the Crop Diversification Centre North near Edmonton, Ampong-Nyarko found excellent weed suppression when 20 to 30 grams of pennycress meal were applied to the holes in the plastic mulch. No negative effects were observed on the rhodiola. Rhodiola is being studied as a medicinal plant at CDC North.
The meal might also be considered as a valuable organic fertilizer, with about four percent nitrogen and 0.7 percent phosphorus. Injury to crops can be avoided by applying more than two weeks before seeding.
Producers could take advantage of this information by keeping in mind four possibilities: the use of screenings, wild crafting, green manuring and cropping.
Using weed screenings as a source of biodiesel, herbicide, feed and fertilizer could add value to products taken from the field.
Wild crafting offers another opportunity that otherwise would be wasted.
“It is feasible to harvest wild stands of pennycress using conventional combines,” said Ampong-Nyarko. “Seed yield of self-seeded winter pennycress harvested in July ranged between 1,980 and 2,560 pounds per acre.”
Weedy fields could also be used as green manures. As well, because stinkweed is often dominant in the spring, cultivation may provide some weed control, but further research is required.
A more extreme option is growing pennycress as a field crop.
“Pennycress has a lower break-even cost than canola” said Ampong-Nyarko.
“We have obtained a non weed status for pennycress, thus paving the way for its cultivation as a crop in Alberta.”
Ampong-Nyarko has studied the agronomy of pennycress and has developed cultivation techniques.
However, using a weed as a crop poses potential problems. Natural seed dormancy means that some of the seed sown one year will emerge in following years. Harvest losses will increase this problem.
Extra care must be taken in designing a rotation capable of dealing with the added seed input.
Ampong-Nyarko recommends following three years of field pennycress with a winter cereal.
Research suggests we may be able to convert a weed into an opportunity.
Brenda Frick, Ph. D., P. Ag. is an organic research and extension specialist. She welcomes your comments at 306-260-0663 or via e-mail at
———
