Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 13, 2005
Publication Date: August 30, 2005
Citation: Burner, D.M., Pote, D.H., Ares, A. 2005. Management effects on biomass and foliar nutritive value of Robinia pseudoacacia and Gleditsia triacanthos f. intermis in Arkansas, USA. Agroforestry Systems. 65(3):207-214. Interpretive Summary: Ranchers of the southeastern USA often have to resort to expensive, supplemental hay feeding during summer when growth of conventional plants is constrained by reduced rainfall and high air temperatures. Deep-rooted trees could be used for livestock feed during dry summer months to broaden forage options, reduce costs, and increase livestock gain, but few tests have been conducted on their yield or quality. We examined effects of fertilization and pruning height on monthly leaf yield and quality of black locust and thornless honey locust. Black locust had high yields of nutritious forage in August when other forages typically are low yielding, and was faster growing, yielded more forage, was more drought tolerant, and lacked thorns, as compared to thornless honey locust. These results are of interest to other scientists, extension personnel, and ranchers because they show that black locust can provide high yields of quality livestock feed when summer drought reduces yield of other forages.
Technical Abstract: The browse potential of black locust (Robinia pseudoacacia L.) and thornless honey locust [Gleditsia triacanthos f. inermis (L.) Zabel] has not been adequately tested. Our objective was to determine effects of fertilization and pollard height on biomass and foliar nutritive value in separate studies of black locust and thornless honey locust in Arkansas, USA. Shoots were sampled monthly for two consecutive growing seasons to determine foliar, shoot, and total aboveground biomass, shoot basal diameter, and foliar nutritive value (crude protein and in vitro digestibility). Black locust yielded more foliar biomass when pollarded at 50- or 100-cm and fertilized with 600 kg P/ha, than at 5-cm with or without P, averaging 3.5 Mg dry matter/ha. Shoot basal diameter was predictive of foliar, shoot, and total aboveground biomass of black locust (R-squared = 0.52 to 0.79), but not for foliar yield of thornless honey locust. Black locust foliar crude protein and in vitro dry matter digestibility (> 170 and 534 g/kg, respectively) decreased as leaves aged, but still met or exceeded maintenance needs for beef cattle (Bos taurus L.). Thornless honey locust had less agronomic potential than black locust because of its slower growth, low yield (250 kg/ha), poor drought tolerance, and a slight tendency for reversion to undesirable thorny phenotype. Black locust should be considered for livestock browse when drought induces semi-dormancy of herbaceous forages.