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*Did you know that alfalfa is the most widely grown forage legume in the world? However, yield gains have not occurred at the same pace as other crops over the past 50 years. It is more difficult to obtain yield gains from perennials than from annuals. Alfalfa varieties have improved, but yield gains have been slow.
Traditionally, genetic selection for increased alfalfa yields has focused on the aerial characteristics of the plant, largely ignoring the potential contribution of the root system to improved yields. However, the latter can contribute by facilitating access to water and nutrients.
Researchers at the University of Minnesota are increasingly interested in the root system, saying that most alfalfa is underground with roots that grow up to 5 feet per year and up to 30 feet long. It’s no surprise that root structure plays a significant role in alfalfa productivity. Roots have the potential to influence nitrogen fixation, nutrient uptake, water use efficiency, plant resistance to elevation, winter hardiness and pest tolerance.
Alfalfa roots can be classified into 4 types:
- pole
- Branches (bundled, branched)
- Plotters
- Rhizome
Most modern alfalfa cultivars have a taproot. Studies of alfalfa roots are tedious and uncommon, but new techniques have recently been developed to generate digital images of the roots, speeding up the process.
In a study by Deborah Samack, alfalfa plants were crossbred into high- and low-fiber populations and sorted according to whether they were branched or branched. These populations were evaluated over two years. Forage yields of plants selected for their fibrous, branched roots were 7 to 14% higher during the establishment year and 9 to 16% higher during the first year of production than alfalfa.
The study therefore suggests that breeding modified root morphology is a viable strategy for improving alfalfa productivity. In fact, these plants had more nodules than those with primary roots, which could mean better nitrogen fixation. It is also possible that the rooting branches allow the plants to access more nutrients from the soil.
There are still many questions to be answered regarding the engineering of alfalfa roots. It is possible that plants with taproots have an advantage in storing carbohydrates to survive the winter or being more resistant to drought conditions. Conversely, plants with branched roots may give plants an advantage in moist soils where gas exchange is high.
In short, everything is not black and white. Different types of root systems bring interesting aspects to the field. Why not choose a mix of both types to reap all the benefits!
*The text was produced by Roselyn Goupil, in collaboration with the Council of Quebec Feed Mills (CQPF). However, the comments contained in the text are those of the author alone and do not represent the views of the CQPF.
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