05. June 2020
Perennial plants are taking root
Rethinking the agricultural system
By Laura von Ketteler
For thousands of years, plant breeding has concentrated on annual plant cultures. Initially, farmers planted crops that were very similar to their wild relatives. By crossing and selection, harvests could be increased and more people could be fed. The cultivation of corn, wheat and rice spread all over the world. Everywhere the rhythm of agriculture developed in the same way, sowing begins in spring and the harvest takes place in autumn. However, this is not the rhythm dictated by nature. The majority of wild plants are perennial, they are responsible for a functioning ecosystem and with their root system and biomass they provide stability and diversity in nature. Perennial plants are therefore the focus of science and agriculture.
Today, annual crops, such as corn, weed, ray, rice, barley and most vegetables, account for around 70 percent of the human population’s food intake and the majority of planted cropland worldwide. “Annuals were important for the Green Revolution and have ensured that crops can be grown on a wide scale. However, they are only as successful today because there is a large input of herbicides, fertilizers and irrigation and the use of tillage is taking place”, says Maria von Korff, leading scientist of the Institute of plant genetics at Heinrich Heine University in Düsseldorf, Germany.
To grow annuals successfully weeds are being suppressed implementing hoes and plows before planting them. Soil disturbance has caused soil carbon loss, nutrient leakage, and soil erosion. The modern methods of agriculture have their cost. Approximately, 24 billion tons of healthy soil are lost worldwide each year. Additionally, pesticides and fertilizers affect the groundwater quality and intense infiltration oversalts the soil.
To the roots of perennial plant research
Researchers around the world ask themselves if it is possible to rethink the agricultural system as it is and to change it to an environmentally friendly one: a system that is adapted to natural ecosystems. Growing perennials is one approach that promises a transition towards a regenerative agricultural system. The idea: Perennial plants do not have to be reseeded or replanted every year, so they do not require annual plowing or herbicide applications to establish.
In the state of Kansas, amongst a huge agricultural industry, the Land Institute, a nonprofit research institute, is working on exactly these questions. For the founder Wes Jackson one thing has always been clear: Nature as measure has been his motto for decades. The Land Institute seeks to develop an agricultural system that uses natural systems – in preference over extractive industrial systems – as the measure of productivity.
Today the scientists from the Land Institute do research on perennial oilseeds such as Silphium integrifolium which could replace sunflower. The also do research on raps and legumes such as lupine and lucerne. The biggest success in their research has been on grains and so called Kernza, a perennial relative of wheat and the first perennial grain that has been cultivated commercially. The outdoor brand Patagonia brews beer from Kernza called the “Long Root Pale Ale” and eco bakeries use it to bake bread.
The Land institute has two approaches in developing perennial plants. First, domesticating wild perennial plants. Populations of the crop are grown out at the Institute, and plant breeders select the best individuals for the traits of interest. The individual plants are then cross-pollinated, and the resulting seeds are planted to produce the next improved breeding population. The second approach is perennialization of existing crops. This means crossing an existing annual grain crop with a wild perennial relative.
Approaches to various varieties
“To develop Kernza we have combined annual wheat genes with wild perennial wheat relatives”, says Land Institute lead researcher Lee DeHaan. “But we are still working on improvements, as it is not really economically viable. In the end the most important factor is that yield can keep up with conventionally grown crops”, he explains. Kernza lives on approximately three to four years and can be swathed and collected with a pick-up header or direct harvested with a stripper header or grain header on a combine adjusted for its small size and light seed. But today weed produces four times more corn than Kernza, still it could be the beginning of a success story in the research of perennials.
The so called PR23, a perennial rice which has been developed in China in cooperation with the Land Institute offers an even more successful approach. “The yield is comparable to the conventionally grown rice and it has several advantages. It saves a lot of manual work and can be harvested twice a year” knows von Korff. In China PR23 is already planted on thousands of hectares.
Initial research is also being conducted in the vegetable sector. Hanno Schäfer, TU München, hopes for the establishment of perennial vegetables and fruits. With his team he discovered relatives of the honey melon in Australia and India. “Especially in dry areas such as north Africa and dry regions of India, where the effects of climate change are the strongest, perennial vegetables could have a huge potential” he says. Perennial honey melons could most probably maintain for five to ten years. Schäfer is of the opinion that not crossing and selecting is the way to go here but CRISPR CAS.
Advantages of perennial crops
What makes perennials so promising that scientists come up with the patience for research that will take decades until it will show some success? “Perennials have several advantages and answers to current challenges in agriculture” DeHaan explains. “Over the years perennials have develop a really deep root system which is more tolerant to droughts. In general, they don’t show stress nearly as soon as annuals do” he adds.
Scientists are of the same opinion that perennials are likely to have a higher resistance to pests because they have time to develop resistance over several years. The clue will be to combine the best aspects from annuals and perennials in order to increase yield stability, resilience to pests and tolerance towards droughts. “On the other side perennials are also likely to take longer to recover if they are affected by pests or severe weather extremes” DeHaan points out.
If the yield will be comparable to conventionally grown crops, farmers could additionally to environmental benefits safe money they usually spend on labor, petrol, seeds and especially on one thing farmers spend most money on: nitrogen fertilizer.
What do we need for the future?
Discovering new varieties is one thing, but an even bigger challenge could be to reform the agricultural system as it is. Several industries along the value chain, such as the seed-, fertilizer- and machinery industry is dependent on annual processes. “Fast profit is not to be made with perennials and it will be difficult to break through existing production chains” von Korff believes.
DeHaan and von Korff agree that perennials will not replace the agricultural system as it is today, but they will offer a good alternative in areas that are affected by droughts or erosion. To be able to continue this long-term research, further publicity and more importantly funding is needed.