Agroforest Syst (2008) 72:51–62 DOI 10.1007/s10457-007-9098-x Yield components and nutritive value of Robinia pseudoacacia and Albizia julibrissin in Arkansas, USA David M. Burner Æ Danielle J. Carrier Æ David P. Belesky Æ Daniel H. Pote Æ Adrian Ares Æ E. C. Clausen Received: 13 June 2007 / Accepted: 2 October 2007 / Published online: 20 October 2007 Ó Springer Science+Business Media B.V. 2007 Abstract Ranchers need alternative livestock feeds Black locust exceeded mimosa for every yield com- when herbaceous forages become limiting in summer. ponent (leaf mass tree–1, leaves shoot–1, shoots tree–1, Our objectives were to determine: (1) leaf and stem shoot mass tree–1, stem basal area, and biomass tree–1) biomass components, (2) nutritive value [in vitro dry except mass leaf–1. Projected yields were 1,900 and matter digestibility (IVDMD), total nonstructural 1,600 kg leaves ha–1 for black locust and mimosa, carbohydrate (TNC), N, and N digestibility] of leaves respectively, assuming a population of 12,300 trees for animal browse, (3) concentration of the secondary ha–1. Mimosa leaves had greater IVDMD, TNC, and N metabolites robinin and mimosine, and (4) in vitro leaf digestibility than black locust. Mimosa leaves and bark toxicity for black locust (Robinia pseudo- exceeded the nutritional N requirements of growing acacia L.) and mimosa (Albizia julibrissin Durz.), cattle (Bos taurus L.) and goats (Capra hircus L.), but respectively, pollarded at 50 cm in Arkansas, USA. protein supplementation would be needed for growing goats grazing black locust leaves. Tissue concentra- tions of secondary metabolites robinin and mimosine D. M. Burner (&) Á D. H. Pote Dale Bumpers Small Farms Research Center, United were below detectable limits in black locust and States Department of Agriculture, Agricultural Research mimosa, respectively. The extract of black locust bark, Service, 6883 South State Hwy. 23, Booneville, but not leaves, was toxic to bioassayed African green AR 72927, USA monkey (Cercopithecus aethiops L.) cells. Either black e-mail: [email protected] locust or mimosa could provide moderate quantities of D. J. Carrier high quality, rotationally grazed forage for goats Biological and Agricultural Engineering, University of during summer months when herbaceous forage may Arkansas, Fayetteville, AR 72701, USA in short supply. D. P. Belesky Appalachian Farming Systems Research Center, United Keywords Black locust Á Crude protein Á States Department of Agriculture, Agricultural Research In vitro dry matter digestibility Á Mimosa Á Service, 1224 Airport Rd, Beaver, WV 25813, USA Mimosine Á Nitrogen Á Pollard Á Robinin A. Ares Forest Science, Oregon State University, Corvallis, OR 97331, USA Introduction E. C. Clausen Ralph E. Martin Department of Chemical Engineering, Black locust (subfamily Faboideae) and mimosa University of Arkansas, Fayetteville, AR 72701, USA (subfamily Mimosaceae) are tree species in Fabaceae 123 52 Agroforest Syst (2008) 72:51–62 Lindl. that could be used for livestock browse in USA (Williams et al. 2000; R. D. Williams, 2006, personal and other countries. Both species are invasive in communication). some ecosystems (Mullen et al. 2000; Rice et al. The objectives of this study were to determine: 2004), and their browse is highly preferred by goats (1) leaf and stem biomass components, (2) nutritive (Luginbuhl and Mueller 1999). Goats fed black locust value [in vitro dry matter digestibility (IVDMD), leaves in summer had similar live weight gain total nonstructural carbohydrate (TNC), N, and N ([100 g day–1) as goats fed alfalfa (Medicago sativa digestibility] of leaves for animal browse, (3) quan- L.) pellets (Papachristou et al. 1999). Voluntary tities of the secondary metabolites robinin and intake of alfalfa meal and black locust leaf meal mimosine, and (4) in vitro leaf and bark toxicity for did not differ for sheep (Ovis aries L.) in a study in black locust and mimosa trees pollarded at 50 cm in which weight gain was not measured (Horton and Arkansas, USA. Christensen 1981). Nutritive value analysis (Baert- sche et al. 1986; Burner et al. 2005) suggests that black locust has potential as livestock feed. Materials and methods The feed value of black locust leaves has been debated for some time mainly because of the The experiment was situated on a Linker soil presence of antiquality components. Black locust is (fine-loamy, siliceous, semiactive, thermic Typic toxic to the horse, Equus caballus L. (Ball et al. Hapludult) near Booneville, Arkansas (35.11°N, 1996) but not to goats (Cheeke 1992; Govt. of 93.95°W; 152 m above sea level). Initial composition Canada 2006). It is not known if black locust is toxic of the topsoil (15-cm depth) was pH 5.5, 15 kg P ha–1, to cattle or sheep. Data are limited or contradictory 450 kg K ha–1, and 1.57 g N kg–1. Fertilizer was on specific leaf toxins, toxin concentrations, critical applied to the soil surface at the rate of 55 kg P ha–1 toxicity levels for ruminants, and whether cultural and 55 kg K ha–1 in March 2001, and 340 kg P ha–1 in practice might influence toxin concentrations. Data March 2002. also are limited on secondary metabolites in black One-year-old black locust trees (Lawyer Nursery locust. The nontoxic flavonoid robinin (kaempferol- Inc., Plains, MT, USA) and 2-year-old mimosa trees 3-O-robinoside-7-O-rhamnoside), a complex of iso- (started from seed collected in Oklahoma, USA) were meric forms of a triglycoside, occurs in Robinia spp. inoculated by dipping roots in species-specific strains flowers (Maksyutina 1972; Sando 1932), but presence of Rhizobium spp. (Liphatech, Milwaukee, WI, in leaves is not documented. Robinin has antioxidant USA). Trees were transplanted in February 2002 at properties that benefit human health, and could be a a spacing of 0.9 m within and between rows value-added flavonoid extracted prior to biofuel (12,300 trees ha–1). There were four contiguous rows conversion (Lau et al. 2005). of each species in each plot. Trees in the center two Less is known about the nutritive value of mimosa rows were for sampling while those in the outer two than black locust. Mimosa leaves have less neutral rows served as buffers. Alleys were mowed period- detergent fiber (NDF), acid detergent fiber (ADF), and ically to control herbaceous vegetation. crude protein (CP), and is less preferred by goats than Immediately after transplanting, height and basal black locust (Addlestone et al. 1999). An unidentified stem diameter were measured for about 20 trees plot– water insoluble, nonalkaloid constituent present in 1. During establishment, dormant trees were pollard- pods and seeds of at least two Albizia species causes ed at 50-cm height above soil surface in March 2003 cattle toxicity in southern Africa (Basson et al. 1970). and January 2004 to stimulate shoot proliferation. Mimosine [b-N-(3-hydroxy-4-pyridone)-a-aminopro- Dry mass of pollard clippings was measured for about pionic acid] is a toxic alkaloid present in leaves of 20 trees plot–1. At this location during November Leucaena spp. (Soedarjo et al. 1994). Mimosine in through April, these species are dormant due to cold Leucaena leucocephala decreases in concentration temperatures and daylength. During the study, dor- with leaf age, from 45 g kg–1 in 1-week-old to 2 g kg–1 mant trees also were pollarded in December 2004. in 10-week-old leaves (Tangendjaja et al. 1986). A stationary weather station (Spectrum Technol- Mimosa does not appear to have been tested for ogies, Inc., Plainfield, IL, USA) was located 4 km mimosine despite anecdotal evidence of its presence west of the study site. Data including air temperature 123 Agroforest Syst (2008) 72:51–62 53 (measured by a thermocouple at 1.5 m above soil 29 surface), soil temperature (measured by a thermo- a 28 couple placed 15 cm below soil surface under grass ) sod), and rainfall (measured with a tipping bucket C 27 o recorder at 1.5 m above soil surface) were recorded at r u( 26 0.5-h intervals in July through September 2004 and r ete 2005. Long-term (1971–2000) air temperature and 25 ma rainfall data for Booneville, AR, USA (NOAA 2002) were used for reference. Air temperature was lower 24 aairtep during July–September 2004 than in the same months e 23 Mn of 2005 or the long-term mean (Fig. 1a), whereas soil temperature was lower in August 2004 than in August 22 2005 (Fig. 1b). More rainfall was received in July 21 2004 and September 2005 than the long-term mean 29 for the same months, but rainfall was similar to the 2004 b long-term mean in August 2004 and 2005 (Fig. 1c). 28 2005 ) C 27 o Long-term r Yield measurements u( 26 r ete 25 Four trees were harvested at random from each plot ma itep in July, August, and September 2004 and 2005. These 24 months were selected because forage quality and asol e 23 quantity can become limiting in pastures and range- Mn land in the southern USA. Shoots were clipped from 22 the main stem at 50-cm height above soil surface and counted. Basal area tree–1 (mm2) was calculated as 21 2004 200 2005 the sum of basal diameters of each clipped shoot c measured 2 cm distal to the cut. Leaves (petioles and Long-term leaflets) were removed from the clipped shoots, 150 including 5–10 cm of unlignified shoot apex. Leaves and shoots were counted and combined for the four m sampled trees per plot. Leaf and shoot dry mass were ( l l 100 a measured after oven drying (60°C) for 48 and 120 h, f) nm i respectively.