NEW CROPS Kenaf Forage Yield and Quality under Varying Water Availability

stalks. Similar results were reported by Bhardwaj et al. (1996) for kenaf consumption by goats (Capra hicus). A broadleaf forage crop grown in rotation with winter wheat (TritiUnger (2001) in the Texas Panhandle (average annual cum aestivum L.) would diversify dryland crop rotations in the central Great Plains. Kenaf (Hibiscus cannabinus L.) provides good quality precipitation 475 mm; average June through October livestock forage, but yield and quality have not been evaluated under precipitation 303 mm) concluded that kenaf had only varying water availability conditions. This study determined kenaf limited potential as a dryland forage crop on the southsoil water extraction, plant height, regrowth following cutting, dry ern high plains of the United States because of low plant matter (DM) yield, and forage quality responses to varying water material yields (2300 kg ha 1). On the other hand, he availability. Kenaf was planted on a Weld silt loam (fine, smectitic, suggested that the high protein content of kenaf [327 g mesic Aridic Argiustolls) under a line-source gradient irrigation syskg 1 at 65 d after planting (DAP) declining to 195 g tem. Water conditions ranged from rainfed to full evapotranspiration kg 1 at 121 DAP], along with its higher potential yield replacement. Kenaf was harvested in early August and then again in where precipitation was greater, could make it a useful October. Dry matter yield increased linearly with increases in available forage crop where precipitation was more reliable. Philwater and water use, with about 2000 kg ha 1 DM yield produced with 274-mm water use increasing to 6000 kg ha 1 with 507-mm water lips et al. (1999) in Oklahoma also reported that wholeuse. Crude protein (163 to 279 g kg 1) decreased with increasing water plant CP of kenaf declined with time from 223 g kg 1 use. Neutral detergent fiber (229 to 478 g kg 1) and acid detergent at 40 DAP to 154 g kg 1 at 101 DAP. Vinson et al. fiber (168 to 314 g kg 1) increased with increasing water use. Total (1979) similarly found CP declined from 246 g kg 1 at digestible nutrients (656 to 840 g kg 1) and relative feed value (range 30 DAP to 47 g kg 1 at 105 DAP for kenaf grown under 130 to 308) decreased with increasing water use. For a given amount irrigation in Arizona. Similar results of declining CP of water use, kenaf DM yield was lower than corn (Zea mays L.) with increasing plant age have been reported by Muir silage, but kenaf crude protein production was higher than corn silage (2001), Swingle et al. (1978), Webber (1993), Phillips et (73–215%). Kenaf appears to be a high quality livestock forage that al. (1999), Vinson et al. (1979), and Bhardwaj et al. has potential as both an irrigated or dryland crop in the central (1996). Changes in kenaf CP with water availability have Great Plains. not been documented in the literature. Phillips et al. (1999) reported 3-yr average DM yields of 8644 kg ha 1 at 101 DAP with about 200 mm of T traditional wheat–fallow dryland production growing season precipitation. Unfortunately, the irrigasystem of the central Great Plains is gradually being tion amounts applied were not clearly specified. They replaced by cropping systems that include other crops. concluded that harvesting kenaf at 70 to 80 DAP would The diversification of crops includes corn, proso millet optimize digestibility and N concentration of the stalks (Panicum miliaceum L.), sunflower (Helianthus annuus and maximize the proportion of leaf DM in the whole L.), and forage and seed legumes (Anderson et al., 1999; plant. Dicks et al. (1992) stated that the optimum growth Peterson et al., 1996; Nielsen et al., 1999; Nielsen, 2001; period for kenaf to produce maximum leaf/stem ratio Vigil and Nielsen, 1998). Another potential forage crop and highest quality forage was 60 d. Webber (1993) to diversify cropping systems in this region may be reported 2-yr average kenaf yields in Texas of 4764 kg kenaf. ha 1, with 404 mm of precipitation from planting to 76 Kenaf is a warm-season annual that, when mature, DAP, and 7512 kg ha 1, with 476 mm of precipitation can produce fiber for rope, carpet backing, and paper. from planting to 99 DAP. In that study, whole-plant CP Kenaf could provide a high-protein forage for integrated was found to be much lower than in many other reported crop–livestock operations without the multiyear comstudies (60–80 g kg 1). Muir (2001) in central Texas mitment of land and resources required of alfalfa (Medfound a strong kenaf DM increase in response to inicago sativa L.). Some studies have been done showing creased growing season precipitation, but the producthe forage characteristics of immature kenaf and demtion function was not calculated. In that study, 2359 kg onstrating its feasibility as a potential livestock feed. ha 1 was produced after 90 d of growth in a dry year Phillips et al. (1996) observed that lambs (Ovis aries) compared with 5064 kg ha 1 in a relatively wetter year. readily consumed leaves, stems, and immature kenaf Muir et al. (2001) reported a 2-yr average DM yield of 13 762 kg ha 1 for kenaf grown with 448 mm of growing USDA-ARS, Central Great Plains Res. Stn., 40335 County Road GG, season precipitation and 435 mm of supplemental irrigaAkron, CO 80720. Received 2 Dec. 2002. *Corresponding author ([email protected]). Abbreviations: ADF, acid detergent fiber; CP, crude protein; DAP, days after planting; DM, dry matter; DP, digestible protein; NDF, Published in Agron. J. 96:204–213 (2004).  American Society of Agronomy neutral detergent fiber; RFV, relative feed value; SAI, silhouette area index; TDN, total digestible nutrient. 677 S. Segoe Rd., Madison, WI 53711 USA