Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/25/2003
Publication Date: 1/15/2004
Citation: NIELSEN, D.C. KENAF FORAGE YIELD AND QUALITY UNDER VARYING WATER AVAILABILITY. 2004. AGRONOMY JOURNAL 96:204-213. Interpretive Summary: Cropping systems in the central Great Plains would benefit from the diversity introduced with production of a broadleaf crop in rotation with winter wheat. Kenaf produces a high quality forage and needs to be tested for productivity and forage quality under dryland conditions in the central Great Plains. This study found that kenaf forage production responded linearly to increased water availability, with average yields likely to be about 4700 kg/ha (dry weight). Total dry matter production would be less for kenaf than corn silage under similar water availability conditions, but kenaf's higher crude protein concentration results in 55 to 84% higher crude protein production per hectare compared with corn. Kenaf stubble remaining after harvest is sufficient to eliminate possible soil erosion by wind, and to aid in soil water recharge by snow catch. Kenaf appears to be a viable alternative forage crop for the central Great Plains.
Technical Abstract: A broadleaf forage crop grown in rotation with winter wheat is needed to diversify and enhance dryland crop rotations in the central Great Plains. Kenaf (Hibiscus cannabinus L.) has been reported to provide good quality forage for livestock, but forage yield and quality have not been evaluated under varying water supply conditions. This study was conducted to determine kenaf soil water extraction, plant height, regrowth following cutting, forage yield, and quality responses to varying water availability. Kenaf was planted under a line-source gradient irrigation system to provide a range of available water conditions (rainfed to full evapotranspiration replacement). Kenaf was harvested in early August, leaving a 20 cm stalk for regrowth, and then harvested again just prior to the first autumn frost. Soil water content, crop water use, and forage yield were measured to produce water use-yield relationships. Forage quality was assessed from measurements of crude protein, neutral detergent fiber, acid detergent fiber, and total digestible nutrients, and calculated relative feed value. Biomass production increased linearly with increases in available water and water use, with about 1000 kg ha-1 dry matter produced with 25 cm water use increasing to 6000 kg ha-1 with 50 cm water use. Crude protein ranged from 16 to 28 g kg-1, decreasing with increasing water use. Neutral detergent fiber ranged from 23 to 48 g kg-1 and acid detergent fiber ranged from 17 to 31 g kg-1, both increasing with increasing water use. Both total digestible nutrients (range 66 to 84 g kg-1) and relative feed value (range 130 to 308), decreased with increasing water use. For a given amount of water use, kenaf dry matter productivity was lower than corn silage, but kenaf crude protein productivity was higher than corn silage (55 to 84%). Kenaf appears to be a high quality livestock forage that has potential as both an irrigated or dryland crop in the central Great Plains.