Kenaf (Hibiscus cannabinus) and Sunn Hemp (Crotalaria juncea): Monoculture and Polyculture Production.

Kenaf (Hibiscus cannabinus L.) and sunn hemp (Crotalaria juncea L.) are fast growing summer annual crops with numerous commercial applications (fibers, biofuels, bioremediation, paper pulp, building materials, cover crops, and livestock forages).  Field research was conducted in southeast Oklahoma (Lane, OK) to compare monoculture and polyculture production of these two crops.  The experiment was arranged in a randomized complete block design (RCBD) with 3 planting regimes, 4 harvest dates, and 4 replications.  Kenaf, ‘Tainung #2’, and sunn hemp, ‘Tropic Sun’, were planted on 1 June 2009 on a Bernow fine sandy loam, 0-3% slope (fine-loamy, siliceous, thermic Glossic Paleudalf) soil in 4 rows with a 76 cm spacing between rows in plots 3 m wide and 9.1 m long.  Kenaf and sunn hemp were each planted as monocultures with final population stands of 430,547 plants ha^-1, and as a polyculture with a combined plant stand of 430,547 plants ha^-1.  Kenaf and sunn hemp plants were harvested at 45-, 90-, 135-, and 177-days after planting (DAP).  Plant height, stalk diameter, leaf and stalk yields were determined for each harvest.  Kenaf leaf and stalk yields were greater than sunn hemp when comparing within the polycultures and between the monocultures.  Stalk yields and stalk biomass percentages for both crops increased with each harvest date across cropping systems.  Leaf biomass percentages decreased with each harvest date and leaf yields peaked at 135 DAP.  The monoculture of each crop produced as good, or better, crop yields and individual stalk parameters (plant weight, plant height and stalk diameter) than crops grown in polyculture.  These results provide no short term incentive for producing kenaf and sunn hemp in polyculture.