Chapters 5.58

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5.58 -Sweet Clover as a Forage Legume Yellow Sweet Clover - Melilotus officinalis & White Sweet Clover - Melilotus albus


Katrina Grise , University of Guelph, Canada

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Suggested citation for this chapter.

Grise,K. (2022) Sweet Clover as a Forage Legume Yellow Sweet Clover - Melilotus officinalis & White Sweet Clover - Melilotus albus, In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Background

Sweet Clover “Melilotus officinalis” and “Melilotus albus” is a green manure legume that is native to Eurasia (Europe, Central Asia, and India) (Cover Crop Database) and has been introduced to North America, Africa and Australia. It is versatile with multiple applications including use as a forage crop and restorative cover crop that adds nutrients to soils. This crop would be beneficial in some parts of Africa, Caribbean and South Asia where soil remediation is a substantial concern (Hoyos, 2017). In addition to the difference in colour between the white sweet clover and yellow sweet clover varieties, both have different qualities (Kirk and Stevenson, 1931). Historically, white sweet clover seed costs more than yellow sweet clover (Madson, 1980)

Rainfall and Temperature and Requirements Role in Combating Climate Change

Clover is versatile and can grow in diverse climates (Panagos, 2017). Climate change is resulting in larger areas of drought and extreme weather/season unpredictability. Sweet clover is a drought tolerant crop with a mid length to short growing season (Panagos, 2017). Optimal rainfall for sweet clover is only 432 mm or more thorough the growing season, though Yellow sweet clover is found to be more drought tolerant (McLeod, 1982). Sweet clover growth is dependent on the spring soil saturation that comes with winter melts, especially at the germination stage. During the beginning stages of sweet clover growth, there is typically an abundance of moisture. Another advantage of sweet clover is that it is low growing and works efficiently to suppress weeds (Ontario Ministry of Agriculture, 2020). Weeds often take advantage of bare patches that become abundant under dry conditions. Due to its deep roots, the crop is optimal for erosion control such as in hillside farming (Panagos, 2017). Sweet clover can be grown in areas that do not exceed 42°C and do not drop below -4°C for more than five consecutive months (Ontario Ministry of Agriculture, 2020), though more heat tolerant varieties may exist.

Benefits and Dangers as a Livestock Forage Crop

As a forage crop for cattle, “sweet clover contained 88.1 to 112.1 per cent as much digestible crude protein and 86.6 to 103.8 per cent as much total digestible nutrients” (Benson, Casper, and Johnson, 1940). Clover as a forage crop is easy to initiate, and it can be intercropped with other forages such as bromegrasses, fescues, wild rye and many more (Yisehak, 2008). The ideal forage crop meets the nutritional needs of the livestock and is native to the area. Not only does this mix work for a forage crop, but it can also be harvested and bailed up and used for winter feed or for the dry season (Yisehak, 2008). Clover can be left in place for foraging after the cash crop is harvested or farmers may choose to harvest the clover and dry it for off season livestock feed (Adhikary et al., 1991). Many smallholders in Africa and South Asia suffer from inadequate livestock feed in the dry season, causing them to sell or slaughter their animals (Hulse, 2003).

It is critical that all farmers planting sweet clover are as a forage crop are aware of the dangers that can accompany it. Sweet clover leaves contain the toxin, warfarin, which is sold commercially as a rat poison (Cover Crop Database). Sweet clover should not be used as the primary forage crop due to the warfarin content which causes early term miscarriages in livestock (Paul, 2005). This is the reason that some farmers are hesitant to uses sweet clover as a forage crop. Farmers in the business of livestock production know the devastating loss of potential new offspring and the costs that accompany that loss (Paul, 2005). Farmers do not need to cut sweet clover from the forage diets completely but may us it in moderation with other forage crops.

As an aside, warfarin can also be used as a natural health supplement for those that suffer from hypercoagulability (hyper blood thickening) conditions (Cover Crop Database). Blood conditions are very temperamental and should be closely monitored by a medical professional, though for those who farm in remote locations and cannot access medical help, this property of sweet clover may offer benefits.

Soil Nutrient Value

Sweet clover adds nutrients to the soil especially nitrogen (Cormack, 1937) by its roots associating with underground rhizobia bacteria that convert atmospheric nitrogen gas into usable nitrogen fertilizer (Hirsch, 2004). Following decomposition, sweet clover acts as a biofertilizer for other crops. Crops such as corn and canola starve soil of nitrogen when grown in succession. Sweet clover roots have the capacity of reaching depth of 2 meters (Rebsomen, 2020; Cormack, 1937) which is prime for rejuvenating damaged soils at hard to reach depths. If rooting depth is desirable to the farmer, sweet clover will grow best if not mowed or grazed in the first year of growth (Ghaderi-Far, 2010). For farmers that have concerns about nutrient and topsoil erosion, the root health of a clover forage crop can make significant preventative/mediation changes. Studies conducted in Saskatchewan, Canada, concluded that in three years of testing with sweet clover for nitrogen restoration, the crops sequentially provided 59, 66, and 70 kg/ha, respectively (Crop Cover Database).

Benefits of Growing Sweet Clover on Hillsides

Hillside farming is a reality that many smallholder farmers are faced with (Chapagain and Raizada, 2017), and erosion is a serious problem. Sweet Clover is not completely shade tolerant though can thrive in low sun (Cover Crop Database) which is an attribute that may make it ideal for farming where solar exposure is not optimal. Sweet clover can be hand planted on those hillsides to form horizontal rows between cash crop rows. Planting in this way will promote a terrace made without earthmoving labour. Where the clover is planted, the roots will prevent erosion and deliver nutrients to the soil that otherwise would wash away.

Weed Control and Pollinator Health Benefits

The lengthy bloom cycle of sweet clover is optimal to help preserve bee and pollinator populations and additionally adds more desirable flavours to honey to make the product more commercially attractive (Rebsomen, 2020). Many farmers use Sweet Clover as a restorative crop instead of using pesticides to eliminate weeds (Iinicki & Enache, 1992). For example, Tansy (Tanacetum vulgar) is a weed that can be challenging to eliminate. If herbicides are used, the soil may take a long time to recover. In that time, legumes will not grow in the soil. If sweet cover were planted instead, it can choke out the Tansy and can be used as a preventative ground cover (Iinicki & Enache, 1992).

Sweet Clover Applications for Smallholder Farmers

In North America, the seeds of sweet clover are typically low in cost (Madson, 1980), as it is not a high demand crop cover. Accessing seeds may be a challenge without the access to online retailers. Though seeding is most efficient if planted using machinery, smallholder farmers will likely be planting their crops by hand. The high germination rates and low cost of sweet clover means that the clover crops can be planted by hand broadcasting, though trench planting would ensure a higher yield (Ferguson, 1967).

Soil remediation is the most common use for sweet clover in North America and parts of Africa because of its remarkable ability to rejuvenate soil nutrient balances (Yisehak, 2008). In order to do this, a farmer will need to know first the best time to seed this crop. Ideally, clover grows best when the seeds can begin to grow in moist conditions, such as at the onset of rainfall (or spring snowfelt in temperate environments) (Yisehak, 2008). Clover seeds are generally more affordable because it is not typically used as a cash crop, so some farmers may choose to plant in mid autumn after harvest of another crop is removed from the fields instead of spring planting (McLeod, 1982). Some of the seeds planted as winter/dry season crops are lost to birds/animals, due to runoff (Yisehak, 2008). Due to the affordability of sweet clover seeds, some farmers take the risk of planting it (Madson, 1980).

Manual weeding is time consuming for smallholder women farmers (Chapagain and Raizada, 2017). Resilient root structures of clovers choke out weeds naturally without the concerns that come with harmful herbicides (Cover Crop Database). Many herbicides stunt the soil health potential of legumes (Rebsomen, 2020). Legume crops may be the primary source of income for some farmers which makes weed control a constant struggle. Roadside ditches are areas often unused and completely full of weeds (Sheard, 2005). Farmers can use sweet clover in areas such as ditches that surround crops to combat encroaching weeds (e.g. dispersing seeds and pollen).

Smallholder farmers may be able to use sweet clover to create a layered farming system that functions as a controlled ecosystem with components that work together. An example of a layered crop would be clover and maize intercropped in the same field to feed livestock, with additional components that can bring in more income to the farmers. Here, the two crops should be planted at an adequate distance of 6 inches / 15.2 cm or more (Martin, 1999). If alternative cash crops were to be intercropped, the root systems would need to be shallower than those of sweet clover’s deep tap roots (Duke, 1981). An additional component that could thrive with the clover and maize and/or livestock would be bees. As already noted above, bee farmers often search for clover crops to put their bees near, not only because the bloom season is so lengthy, but clover honey has a top shelf taste (Rebsomen, 2020)

Additional Constraints of Sweet Clover

Though its deep rooting system has many benefits, tilling the land after sweet clover is more labour intensive (SARE). The post harvest tilling of clover may discourage smallholder farmers. As mentioned above, farmers of livestock are often discouraged from sweet clover due to the warfarin content that is not ideal for reproducing livestock. Even though clover is very hardy, it is not immune to pests such as sweet clover weevil, root borer, and sweet clover aphid (Cover Crop Database). On the second year of the two-year growing cycle, sweet clover stems become too large and woody for livestock consumption (SARE).

References

1. Ontario Ministry of Agriculture, Food and Rural Affairs, (a.d). Retrieved September 27, 2020, (https://www.sare.org/publications/managing-cover-crops-profitably/legume-cover-crops/sweet-clovers/?fbclid=IwAR3hmzvxpIkjAmz7tGVmIM8Atoqom_3ttsxLvfeYEy2S9ZZpKmubwNs1t2k)

2. R. C. Martin, P. R. Greyson, and R. Gordon, Canada Journal of Research, Competition Between Corn and A Living Mulch, (April 27th, 1999) Retrieved October 12th 2020

3. M. W, Cormack, Canadian Journal of Research, Fusarium Spp. As Root Parasites of Alfalfa and Sweet Clover in Alberta, (April 10th, 2011) Retrieved September 30th 2020, (https://www.nrcresearchpress.com/doi/abs/10.1139/cjr37c-037)

4. L. E. Kirk and T. M. Stevenson, Canada Journal of Research, Factors Which Influence Spontaneous Self-Fertilization in Sweet Clover (Melilotus) (September 1st 1931) Retrieved October 12th 2020, (https://cdnsciencepub.com/doi/abs/10.1139/cjr31-071)

5. Sherif, E. A. (2008, October 27). Melilotus indicus (L.) All., a salt-tolerant wild leguminous herb with high potential for use as a forage crop in salt-affected soils. Retrieved November 16th, 2020, from (https://kopernio.com/viewer?doi=10.1016%2Fj.flora.2008.10.004)

6. Cover Crop Database, Sweet clovers, (a.d). Retrieved September 30th, 2020, (https://ucanr.edu/sites/asi/db/covercrops.cfm?crop_id=41)

7. Panos Panagos1, Pasquale Borrelli 2, Katrin Meusburger2, Bofu Yu3, Andreas Klik4, Kyoung Jae Lim5, Jae E. Yang5, Jinren Ni6, Chiyuan Miao7, Nabansu Chattopadhyay8, Seyed Hamidreza Sadeghi9, Zeinab Hazbavi9, Mohsen Zabihi9, Gennady A. Larionov10, Sergey F. Krasnov10, Andrey V. Gorobets10, Yoav Levi11, Gunay Erpul12, Christian Birkel13, Natalia Hoyos14, Victoria Naipal 15, Paulo Tarso S. Oliveira 16, Carlos A. Bonilla17, Mohamed Meddi18, Werner Nel19, Hassan Al Dashti20, Martino Boni1, Nazzareno Diodato21, Kristof Van Oost22, Mark Nearing23 & Cristiano Ballabio1, Scientific Reports, Global rainfall erosivity assessment based on high-temporal resolution rainfall records (2017, June 23) Retrieved December 1st, 2020 (https://kopernio.com/viewer?doi=10.1038%2Fs41598-017-04282-8&token=WzMwMjMxNDMsIjEwLjEwMzgvczQxNTk4LTAxNy0wNDI4Mi04Il0.RYXHYqQl3KFFYNbuwxGvamFHd3I)

8. M.E. Benson, H.H. Casper, and L.J. Johnson, Nutrient and Toxic factors in Sweet Clover (1940) Retrieved December 1st, 2020, (https://library.ndsu.edu/ir/bitstream/handle/10365/5407/farm_38_06_03.pdf?sequence=1&isAllowed=y#:~:text=sweet%20clover%20contained%2088.1%20to,stacks%20(P%22'O.)

9. Kechero Yisehak, Effect of Seed Proportions of Rhodes Grass (Chloris gayana) and White Sweet Clover (Melilotus alba) at Sowing on Agronomic Characteristics and Nutritional Quality (2008, February 20) Retrieved December 1st, 2020

10. S. Adhikary, D . K . Bagchi, P. Ghosal, R. N . Banerjee and B. N . Chatterjee, Studies on Maize-Legume Intercropping and their Residual Effects on Soil Fertility Status and Succeeding Crop in Upland Situation (1991, April 30) Retrieved December 1st, 2020

11. Joseph H. Hulse, Integrated Food Systems for Food Security in a Changing World Environment (July 16-20, 2003) Retrieved December 1st, 2020, (https://kopernio.com/viewer?doi=10.1111%2Fj.1365-2621.2004.tb06318.x&token=WzMwMjMxNDMsIjEwLjExMTEvai4xMzY1LTI2MjEuMjAwNC50YjA2MzE4LngiXQ.NndkWwo6F-AJf4Wwub8fUCvnBII)

12. Karl Paul, The Journal of Biological Chemistry, Hemorrhagic Sweet Clover Disease, Dicumarol, and Warfarin: the Work of Karl Paul Link (2005, February 25) Retrieved December 1st, 2020, (https://kopernio.com/viewer?doi=10.1093%2Ftoxsci%2F66&token=WzMwMjMxNDMsIjEwLjEwOTMvdG94c2NpLzY2Il0.xtFGQCTv7lqUO5B9BOkCTlMxm0c)

13. Walter Giordano & Ann M. Hirsch, The Expression of MaEXP1, a Melilotus alba Expansin Gene, Is Upregulated During the Sweetclover–Sinorhizobium meliloti Interaction (2004, January 28) Retrieved December 1st, 2020, (https://kopernio.com/viewer?doi=10.1094%2Fmpmi.2004.17.6.613&token=WzMwMjMxNDMsIjEwLjEwOTQvbXBtaS4yMDA0LjE3LjYuNjEzIl0.R4l1EtkMMAW32WED0WPEBTUgIUo)

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16. Richard D. Iinicki & Adrian J. Enache, Subterranean clover living mulch: an alternative method of weed control (1992, May) Retrieved December 1st, 2020, (https://www.sciencedirect.com/science/article/abs/pii/016788099290096T)

17. Leeson, JY, Thomas, AG, Sheard, and JW Sheard, Weed distribution across field boundaries adjacent to roadsides (2005) Retrieved December 1st, 2020

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