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Warm-season cover crop mixture of lablab and velvet bean

Cool-season cover crop mixtures are well researched and are cropped around the world, but less emphasis has been placed on warm-season cover crop mixtures. Former ECHO Farm Manager and now Organic Grower, Danny Blank, informed me that he observed the benefits of planting lablab (Lablab purpureus) with velvet bean (Mucuna pruriens), two leguminous vines, at the same time in Florida’s hot and humid summer. Benefits from this mixture include:

  • Large amounts of biomass production that could be chopped down in-place for the next season’s mulch (growing mulch in place)
  • Increased biological nitrogen fixation
  • Weed control over the summer from the very dense vining mat made by the mixture

To test Danny’s suggestions of biomass benefits of the mixture, we planted a small area with both monocultures of lablab and velvet bean as well as mixtures at two different seeding ratios: 75/25 of lablab/velvet bean and 50/50.

All seeds were jab-planted into planting stations with ~50 cm between-row and ~20 cm in-row spacing. Soil in the area is sandy. Before flowering, square meter biomass samples were taken of each treatment with a quadrat made from polyvinyl pipe. Fresh aboveground biomass was recorded for each sample. Subsamples of each species were dried down for dry-weight conversion. The figure below displays the fresh biomass (left) and dry biomass (right) for each cover crop treatment in tons/hectare.

Land equivalence ratios were calculated for the two mixtures based on yields of aboveground biomass (Table 1). Land equivalence ratio relates the yield of a mixture to the yield of the related monocultures grown under the same conditions. Mathematically, it is the sum of two fractions: each fraction of the intercrop yield divided by the monocrop yield. In the below example Y is yield, LL is lablab and VB is velvet bean:

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Given these results, there seems to be a biomass benefit of adding velvet bean to a lablab planting for the context in which these crops were grown. Further research and replication would be needed to further support this observation. Testing these mixtures in different climates and soil types is also important.
The LER fraction of lablab for both mixtures was much greater than 0.5, meaning that lablab gave the yield benefit in both mixtures. When grown by itself, velvet bean outperformed all other treatments. These results relate to the growth habit and the competition between these two species.

Lablab has a very slow initial growth rate, often taking up to a month before vines start to take off. Velvet bean, on the other hand has a very fast growth rate, taking off rapidly after germination (which can be relatively slow). Lablab in monoculture, may experience greater competition with weeds which may take up canopy space and resources. On the other hand, when mixed with velvet bean, the velvet bean takes over early on in the season smothering weeds and lablab later emerges overtop of the mucuna canopy (which is not very high), and covers the mucuna. This is what was observed in this small trial. Early in the season, the mucuna predominates, but the lablab becomes more competitive in the later part of the season.

Results suggest that mixtures could be a tool to extend the time over which GMCCs cover the ground, thereby providing weed suppression. There are many different warm-season annual cover crops that could be grown in different combinations or seeding ratios.

Do you have ideas for other warm-season cover crop mixtures? Have you tried any mixtures in your area?

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Great research Stacy. What research or experience do you have regarding best practices for perennial legumes that work intercropped with shorter vegetables? I have tried Jack Bean this year and it works with taller vegetables and I am looking for a perennial intercropping system for shorter vegetables. I am getting some perennial peanut seeds and later will propagate with rhizomes but seeds are easier to bring in to South Sudan. I plan to establish a permanent ground cover and then slash back and use some mulch around the edge of the planting area to give the vegetables a little distance and a head start before it regrows. I saw a grower doing this here in South Sudan.

Helpful information. A gentleman who attended last year’s ECHO conference in Ft. Myers, Richard Petcher of Petcher Seeds (https://petcherseeds.com/), has researched a wide variety of warm-season cover crop mixtures. He lives in southern Alabama and has been at this for several decades. Richard retired from his work as an extension agent with Auburn before starting his current business. His brother, Steven, is a veterinarian and raises beef cattle and can attest to the weight gains seen on his animals through the hottest parts of the year grazing cattle on some of Richard’s mixes, which is the opposite of what one would expect. Richard is a very generous man and would enjoy sharing with anyone who is interested. His contact information can be found on his website.

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Hey Dan!

I don’t have any personal experience with perennial legume-vegetable systems, but there may be others in our network who do. We did observe a decrease in cassava yields the first season we intercropped them with jack bean. A Network member in Haiti said he experienced similar results, but that in the second season of intercropping, the cassava yields were not negatively impacted by the jack bean.

I used butterfly pea as a perennial ground cover in forage bank plantings in East Africa. It’s a drought-tolerant famine pulse that tends to reseed itself if you are looking for an alternative living ground cover for drylands.

How interesting! I’d love to hear how your slash and grow with vegetables goes. We are currently trialing gliricidia with a maize-legume annual system underneath it. I think you have visited that plot and seen how the system works last year at Conference. We cut back the tree when we seed the maize.

Thanks Jeffery! Richard does have some great warm-season grazing and wildlife mixture suggestions!

The Haiti team I work with has seen an excellent response from velvetbean in a lime orchard. Besides the weed control and nitrogen fixation, velvetbean does not seem palatable for cows and goats. Unfortunately, they have local farmers that will bring their cows and goats in late at night to forage, causing considerable damage to the limes. We would like to introduce lablab as a gm/cc rotation but are afraid of the consequences. It is not possible to fence the properties. Any thoughts on a non palatable gm/cc to use in rotation with velvetbean?

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Great question Gordon!

From my experience, jack bean (Canavalia ensiformis) has low palatability to roaming livestock. There was one person that I knew of who used it as a border around his plot in Tanzania, East Africa. He said that the roaming herds would bump into it, nibble a few leaves and continue on (and not go into his plot of other crops). He had 2-3 rows of jack bean around the border of the field. This may not hold true for very hungry animals or the specific breeds in Haiti, but you could try it on a small scale or with a few plants to see if you have similar experiences.
Has anyone else tried using jack bean to deter animal grazing?

Lablab is very palatable to livestock and some varieties are aggressive climbers, so may climb your lime trees.

Does anyone else have ideas of cover crops that are unpalatable to roaming livestock?