American researcher says one of the benefits of perennial grain crops would be their low input-to-productivity ratio
Soil health is a key measurement when striving to improve the sustainability of global food production.
“To be sustainable, you cannot have an agriculture that depletes the soil source. Eventually it’s going to collapse,” said Tim Crews, director of research at the Land Institute in Salina, Kansas.
Crews, who is working to develop perennial grain crops, said agriculture has a lot to learn from how perennial crops are able to build soil and stay productive for so long.
Crew said all of the world’s grains are annuals, and a significant ecological disturbance is required to grow them, even though they are productive.
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“We essentially have to clear cut all the vegetation on the landscape every year, whether with a plow or herbicides, and re-sow them every year,” he said.
“That comes with a significant cost in terms of sustainability.”
As much as half of the nitrogen applied to annual crops is lost to the environment, he added, and even no-till systems can be susceptible to soil erosion in some areas and have high chemical dependency.
Land-based ecosystems are primarily made up of perennials, but any slight disturbance in the vegetative cover allows annual crops, including weeds, to quickly show up to take advantage of available space and sunshine.
“We put out a welcome map that is as large as could be to invite weed vegetation in. What if we have an agriculture that does not lay out that map?” Crews said.
“These problems don’t exist on the prairie. The prairie kind of just grows itself every year and actually maintains in our part of the world the same level of total productivity as a wheat field, with no inputs,” he said.
Perennialism and biodiversity are two of the drivers of a healthy soil ecosystem, which is what Crews is hoping to incorporate into the cropping system he is studying.
Perennial crops have many benefits, not the least of which is their low input to productivity ratio.
Crews described a study to demonstrate the high level of productivity that prairies can produce with no inputs. It compared Kansas wheat fields that had been in production for at least 70 years with adjacent prairie hay meadow crops.
The wheat fields received 30 kilograms of nitrogen per acre per year, while the prairie hay meadow crops had never been fertilized.
Both crops had been harvested every year for more than 70 years and they exported about the same amount of nitrogen. Twenty kilograms per acre came off both fields at harvest.
However, Crews said 1.2 to 1.7 four more tonnes per acre of soil organic matter were left in the hay meadow than in the annual wheat field.
“The take home for us is that there is some ingenuity in that prairie,” he said.
“We think it has to do with the soil micro-organism, the microbiome. It’s clearly the lack of disturbance that allows it to both hold onto a lot of nitrogen and release a fair amount every year in a timely fashion, so that you can achieve levels of productivity that compares with annual wheat.”
Crews said he is developing a perennial grain crop called kernza that is essentially a bread intermediate wheatgrass selected for seed yield.
“We’ve gone from about three milligrams per seed up to eight, and this is just in 12 years of intensive selection,” he said.
The kernza strain is close to initial commercialization, and growers in Minnesota and Wisconsin are producing the crop. A brewery in Oregon will process it into beer beginning this winter.
“It will be a niche crop like quinoa and other low yielding grain as we continue to improve on the germplasm.”
The Land Institute is also working on a perennial sorghum and wheat, which they are crossing with wild perennial relatives and trying to capture or introgress the perennial traits into the annual crops.
Silphium is another domestication project similar to kernza, which Crews hopes will be a perennial oilseed crop that replaces annual sunflower.
He considers the domestication projects as the tortoise approaches when it comes to variety development because it can take many years to achieve yields comparable to the annual crops with which they will be competing.
Hybrid crosses are the faster approach because they have the potential to create high yielding perennial food crops in a short amount of time.
“We may get lucky rolling the dice and land on a hybrid that actually works,” he said.
“If the perenniality works, we already have the seed quality and the seed traits that make it useful to society,” he said.
The Land Institute is working with a Missouri botanical garden and St .Louis University to create a global inventory of the grass, legume and the aster family sunflower family to identify prospects for future domestication.
robin.booker@producer.com
