Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/12/2004
Publication Date: 11/22/2004
Citation: Burner, D.M., Pote, D.H., Ares, A. 2004. Potential of Gleditsia triacanthos f. inermis and Robinia pseudoacacia for livestock browse: foliar nutritive quality and biomass estimation. Ninth North American Agroforestry Conference - 2005: Moving Agroforestry into the Mainstream, Jodhpur India. International Conference: Multipurpose Trees in the Tropics CD. Session 4. p. 3.
Technical Abstract: Despite a 7-9 month growing season and adequate rainfall (1000-1500 mm), production of herbaceous, C3 forage in the southeastern USA follows a spring-fall bimodal distribution. Insufficient rainfall and high ambient air temperatures during summer often induce semi-dormancy of C3 and C4 species, necessitating expensive, supplemental hay feeding. Deep-rooted trees like Gleditsia triacanthos f. inermis and Robinia pseudoacacia could be used for rotational livestock browse during dry summer months to broaden forage options, reduce costs, and increase livestock productivity. However, the temporal yield distribution and nutritive value of leaf biomass have not been adequately tested. Our objective was to determine effects of fertilization and pollard height on foliar nutritive value, foliar-shoot diameter relationship, and biomass in separate studies of Gleditsia and Robinia. Tests were conducted near Booneville, Arkansas USA (35 deg 05 min. N, 93 deg 59 min. W, 152 m a.s.l.) on a Linker fine, sandy loam soil. The Gleditsia test was a randomized complete block design with three replications. In March 2001, 2-yr-old Gleditsia seedlings (45 to 60-cm tall) were transplanted at 1.4-m spacing into furrows spaced 0.8-m apart created by deep (55-cm) tillage. Nitrogen was applied to Gleditsia at 0, 75, and 150 kg N/ha/yr in split applications. The Robinia test was a split-plot design with two replicates located adjacent to the Gleditsia test on the same soil series. Robinia colonized the site during 2000 and 2001 from existing root stock. P fertilization was the main plot effect (0 and 600 kg P/ha/ yr), and pollard height (stems cut at 5-, 50-, and 100-cm from soil surface) was the subplot effect. Three shoots per plot were sampled monthly from June to October 2002 and 2003 for shoot basal diameter and yield, leaf yield, and leaf crude protein and in vitro dry matter digestibility (IVDMD). Foliar crude protein (>112 g/kg) and IVDMD (>534 g/kg) decreased as leaves aged, but still met or exceeded maintenance needs for beef cattle. Gleditsia was slow-growing and exhibited premature leaf abscission due to moisture stress, while Robinia was high yielding (8 to 9 Mg/ha) during summer. Shoot basal diameter was strongly predictive of foliar and shoot biomass, but linear or non-linear equations varied unpredictably with cultural practice. The generalized equation for foliar yield of Gleditsia was only moderately predictive (R2 = 0.39), but generalized linear and non-linear biomass estimates for Robinia differed <10% from specific equations and were highly predictive (R2 = 0.74 to 0.93). Livestock producers should consider using Robinia pseudoacacia pollarded at 50- or 100-cm for high yields of alternative browse when drought induces semi-dormancy of herbaceous forages.