Sunn hemp studied as alfalfa alternative

Tropical legume may be low-cost forage alternative for short growing seasons or to rescue fields in late-planting years.

Tim Lundeen, Editor

May 24, 2019

3 Min Read
Wyoming sunn hemp2.JPG
Plots of C. juncea at the Sustainable Agriculture Research & Extension Center research station. Photo was taken Aug. 3, 2018. From left to right stands are 45, 32 and 27 days old. Photo taken by Cameron Juma, 2018 SAREC intern.

The success of the Wyoming crop and livestock industry has been limited by market accessibility, infertile soils, short growing seasons and low availability of high-quality, low-cost animal feed, said Carrie Eberle, a University of Wyoming assistant professor of plant sciences.

Eberle thinks the plant Crotalaria juncea, also known as sunn hemp — not to be confused with the recently legalized industrial hemp — may be an answer to help improve crop output. Sunn hemp is a tropical legume that produces high-tonnage biomass in a short time and fixes nitrogen.

Her research project is among 13 headed by University of Wyoming faculty that will benefit from a grand total of $1 million in seed grant funding that is part of the university’s Top-Tier Science Initiative, an announcement from the university said. The Science Initiative Faculty Innovation Grants were awarded to interdisciplinary teams of University of Wyoming faculty.

Eberle's project received almost $90,000 in funding. Dr. Steve Paisley, associate professor and interim director of the University of Wyoming department of animal science, is the project's co-primary investigator.

“We hypothesize the adoption of this crop into Wyoming systems could fit into the short summer growing window, improve soil health, increase soil nitrogen and be used as a high-quality, low-cost alternative to alfalfa hay,” Eberle said. “A knowledge gap exists in how to manage C. juncea for forage harvest, soil improvement properties, yield potential and value as animal feed. With this project, we will establish how irrigation and harvest management affect crop performance and feed quality.”

Eberle told Feedstuffs that C. juncea — which has the "hemp" moniker because it has very fibrous stems — has been reported to produce high amounts of biomass (5-10 tons per acre) and fix large amounts of nitrogen (up to 150 lb. per acre).

She said while they are not yet certain of its full potential in Wyoming, preliminary data suggest that it may have biomass yields of 1.5 tons per acre at about 60 days after planting. "I also have some data on feed quality that shows it is roughly comparable to an alfalfa hay," Eberle added.

She said one of appealing traits of sunn hemp is that it can fit in a short growing season, which may allow flexibility in a crop rotation and "possibly be a good option to rescue fields that have early-season failure or be an alternative for late years like this year where you may not want to plant corn."

Eberle said the study has two main objectives. The first is to understand how to manage sunn hemp in the field, and they are going to look at cutting date, height and regrowth. The researchers want to know how the plant responds but also how the feed quality is affected by management.

The second objective is to focus on the animal side, and Paisley will be conducting studies on both digestibility and feediblilty of sunn hemp.


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