FROID, Mont. — Past agricultural practices have depleted soil organic matter in fields throughout the MonDak. Cover crops could be a remedy, but there are many management questions to be answered, from which crops to grow to the kinds of insects a cover crop might harbor over time.
Against that backdrop, researchers at the Froid Research Farm are taking a deep dive into cover crop science with a test strip planted there with radish, turnip, peas, lentils, and other common cover crops.
Multiple scientists are working in this plot for various studies, teasing out data that can help producers make better management decisions with cover crops.
Dryland agronomist Dr. Brett Allen is crunching numbers on forage yield and quality from the cover crops, while soil scientist Dr. Jay Jabro is measuring compaction and infiltration, to see how they affect soil health. Research ecologist Dr. Tatyana Rand, meanwhile, is assessing the insect populations, both whether pest or predator.
Data from Jabro’s work indicates that compaction issues begin easing in as little as two years, thanks to the work of deep-rooted crops. Decaying roots help create new pore spaces and channels in the soil for water and nutrients to move through.
“This is an inexpensive way to address soil compaction,” Jabro said. “This is the biological way.”
Jabro added that moisture has a profound impact on soil, and that just after a rain is the worst time to decide to take “just one pass” across the field.
“Even one trip can damage the field with 80 percent compaction there,” he said. “And it takes years to restore the soil structure. So stay out of the field when it is wet.”
Allen is tracking forage yields that averaged 1.2 ton per acre in the plot so far, for four years. That’s despite a drought year and a hail year that wiped out many crops at the Froid Research farm.
The cover crops are harvested when the radishes begin flowering to a 4-inch height, and the forage yield and quality are measured. The cover crops are then left to grow until frost, after which the standing biomass is measured. That has averaged 2.8 tons per acre over the four years of the study, which continues to 2021.
Rand is looking at insect populations in the cover crop, and in two oil seeds that might serve as replacements for chemfallow in a two-year durum rotation.
Chemfallow has been found to contribute to erosion and loss of organic matter, as well as tillage hardpans.
Canola is in the same family as Brassica carinata and Camelina sativa, the latter of which are replacements for chemfallow in durum rotations. The oilseeds have potential market in jet fuel.
So far, Rand’s research found that carinata is favored 10 to 1 by flea beetles over camelina.
But carinata was also favored by pollinators, including hover flies, whose larvae are important aphid predators, in addition to growing up to later become pollinators.
Lygus bugs were among the most common pests for both camelina and carinata.
The bug is a generalist that feeds on a lot of different species by puncturing the plant and sipping out the juice. Unfortunately, when it punctures the plant, it also injects a toxin that causes flowers to fall off and reduces seed yields.
In the cover crop, insect pests appeared to be fairly evenly distributed across pest groups with no clearly dominant one. There were aphids, flea beetles and grasshoppers in equal amounts.
Beneficial predators in the cover crop, meanwhile, tended toward spiders and parasitoid wasps.