Sunn Hemp: A Legume Cover Crop with Potential for the Midwest?

Abstract

Crops like corn and soybean occupy vast area in the Midwest, USA. When land is left fallow after the harvest of these crops, a number of degradation factors operate and bring about soil erosion, nutrient loss, decreased soil organic carbon, reduced biological activity and increase in weed biomass. Integrating cover crops (CCs) into this system would build benefits that the very system lacks. There are various CCs available, but leguminous CCs allows for reduced application of fertilizer nitrogen and builds the soil fixed atmospheric nitrogen. Winter CCs are restricted in the Midwest because of the short planting window which greatly minimizes the biomass accumulation. Warm season CCs would serve well here. Sunn hemp is one such tropical CC that grows well in temperate conditions too, without producing seeds. It comes with many benefits -including decreased soil erosion, improved soil organic carbon, increase in soil fixed nitrogen, higher biomass that adds organic matter and N to the soil, reduced weed density and weed biomass. The timing and method of termination influences the residue management. Going by the benefits it adds, sunn hemp is a viable warm season CC that can be grown in the Midwest and has great potential in fallows, prevented plant acres, areas of crop failure (planted and failed) and also in areas after the harvest of the short season small grains or processing crops. However, intensive research on sunn hemp is needed in the Midwest which is discussed.

Sunn hemp biomass accumulation, regrowth, and nutritive value in response to harvest time and cutting height

“…Sunn hemp ( Crotalaria juncea L.) is a tropical legume from India that has use as a green manure, fiber, and forage crop. Research within the continental United States has been limited by access to reliable seed sources until recent breeding efforts conducted at Auburn University began in the early 2000s (Cook & White, 1996; Mosjidis et al., 2013; Shekinah & Stute, 2018).…”

“…Another study reported sunn hemp biomass accumulated 130 lb N acre −1 in 84 days (Cherr et al., 2006). High N content is also accompanied by biomass yields of 2.3–5.4 tons acre −1 in 60–90 days (Blanco‐Canqui et al., 2012; Cherr et al., 2006; Joy & Peterson, 2005 and Shekinah & Stute, 2018). Additionally, sunn hemp biomass nutritive value adequately meets nutritional requirements of beef and dairy cattle as a high‐quality forage source (Katiyar & Ranjhan, 1969; Mansoer et al., 1997; NRC, 1989).…”

Synergy and/or Antagonism in a Cover Crop Sequence: Rotational Effects on Rye in the Midwest

“…Most farmers choose to grow single species solely to enhance the ease of planting operations (Mirsky et al, 2009). activity, decreased accumulation of SOC, and increased weed density (Appelgate et al, 2017;Shekinah & Stute, 2018). Most of these losses occur because of a lack of actively growing plants in the late fall or early spring.…”

Dynamics of Soil Nitrogen Availability Following Sunn Hemp Residue Incorporation in Organic Strawberry Production Systems

“…As a tropical legume, sunn hemp (Crotalaria juncea L.) is adapted to growth conditions found in the southeastern United States and Florida: sandy soils with low fertility characterized by a long warm season (Durairaj and Stute, 2018). Using sunn hemp as a rotational crop in organic strawberry production systems holds great potential for improving soil fertility and quality and environmental sustainability as this high-residue cover crop can help increase SOM, contribute to N supply through N-fixation, reduce weed pressure, and suppress sting nematodes (Belonolaimus longicaudatus), a major soilborne pest for strawberry production in Florida (Blanco-Canqui et al, 2012;Braz et al, 2016).…”