Effect of Kenaf and Soybean Rotations on Yield Components

As kenaf (Hibiscus cannabinus L., Malvaceae) production in the US continues to increase it is essential to integrate this alternative fiber crop into existing cropping systems. Soybean [Glycine max (L.) Merr., Fabaceae] is now grown widely in the same production areas where kenaf can be successfully produced. A kenaf/soybean rotational system could have long term economic and pest control advantages, if there are no adverse effects of rotating these two crops. A three-year field study was conducted at Haskell, Oklahoma to determine the effect of six kenaf/soybean rotations on kenaf and soybean yield components. The kenaf cultivar 'Everglades 41' and soybean cultivar 'Forrest' were planted on a Taloka silt loam soil in mid May and harvested each October. The crops received no irrigation, rainfall was the only source of moisture. The individual kenaf/soybean rotations did not adversely affect the kenaf stalk yields or soybean seed yields. Kenaf stalk yields across all rotational combinations and years averaged 7.9 t/ha, while soybean seed yields averaged 866 kg/ha. Seasonal rainfall affected soybean growth and yields more than any effects due to the cropping sequence. A continuous kenaf rotation produced the greatest kenaf yields (9.4 t/ha) in the final year. It was determined that either a three-year continuous or rotational cropping system can be used for kenaf and soybean production without reducing crop yields. Kenaf is a warm season annual fiber crop closely related to cotton and okra that can be successfully produced in a large portion of the US, particularly in the southern states. For the last 3000 years kenaf has been used as a cordage crop to produce twine, rope, and sackcloth (Wilson et al. 1965). Kenaf was first domesticated and used in north Africa. India has produced and used kenaf for the last 200 years, while Russia started producing kenaf in 1902 and introduced the crop to China in 1935. The US started kenaf research and production during World War II to supply ropes for the war effort and developed high-yielding anthracnose-resistant varieties, cultural practices, and harvesting machinery (Nieschlag et al. 1960; Wilson et al. 1965; White et al. 1970). Then in the 1950s and early 1960s USDA researchers determined that kenaf was an excellent source for cellulose fibers for a large range of paper products (newsprint, bond paper, and corrugated liner board) with less energy and chemical requirements than standard wood sources. More recent research and development work in the …