Optimal Nutritive Value of Honeylocust Seed Pods Within Temperate Silvopasture

Sustainable farms are rare in Appalachia due to severe topography, limited land use potential, lack of diversification, and small farm size (ASA, 1989). Steep slopes and rocky terrain characterize the landscape, making much of it unsuitable for crop production (Proctor and White, 1962). Historically, these lands have been cleared for pasture, despite their tendency to erode and degrade rapidly. In addition, by producing only a single product, farmers in these areas do not take advantage of the diverse, natural environmental niches of Appalachia and limit their ability to cater to various markets. Farm size also constrains the economic sustainability of single-product production systems, as typical Appalachian farms are considered too small (150 acres) to be economically viable (USDA, 1999).

Livestock production on small Appalachian farms using marginal lands is not considered sustainable (Baker et al., 1981). Appalachian farmers typically have limited resources and it is crucial to their livelihoods that those resources be appropriately and adequately utilized to secure environmental and economic sustainability. The purpose of this project is to explore ways of increasing and diversifying production from land resources and to help overcome resource limitations by incorporating trees into pasture-based production systems (silvopasture). 

Silvopasture is a land management system in which trees, forages, and livestock are simultaneously managed on the same area of land. Interactions between trees and ground vegetation result in a complex set of competitive and complementary effects, whose relative impact varies in space and time around trees (Scanlon, 1982; Sharrow, 1991). The benefits of a silvopasture system may include: (1) increased production and nutritive value of cool-season forages in mid-summer; (2) production of additional products such as nuts, fodder, and timber; (3) increased animal comfort due to shade; (4) greater soil fertility due to nutrient recycling and nitrogen fixation; and (5) reduced soil erosion and improved stream quality.

Honeylocust trees have gained particular interest for silvopasture systems. Honeylocust growth patterns (leafing out in late spring) and morphology (open canopy with compound leaves) are ideal for agroforestry in that they minimize competition with forages. Further, the trees have been noted as a potential source of supplemental feed for ruminants. Honeylocusts produce edible seed pods that livestock may consume after pods drop in autumn. Millwood, a high-sugar honeylocust variety produces pods that contain elevated levels of non-structural carbohydrates relative to pods from wild honeylocust trees. Millwood pods may have sugar concentrations as high as 368 g kg-1 (Gold and Hanover, 1993) and the cultivar produces significantly greater pod yields. By one estimate, an acre of well-managed honeylocust trees can produce yields of nutritious fodder comparable to an equal area of oats (Smith, 1950). However, timing of maximum nutritive value is not well defined. Moreover, the utility of pods may vary with animal species. Because cattle lack upper teeth, they may be unable to break the hard seeds and digest the seed proteins. In such case, some degradation may actually improve nutrient availability. Research regarding the nutritive characteristics of honeylocust is thus needed to further clarify this tree’s fodder potential and best management within silvopasture systems.

Honeylocust silvopasture production systems have great potential benefit to small farms by increasing on-farm resources through provision of supplemental energy feed for grazing livestock. Incorporating trees into pasture systems can also improve animal comfort and, depending on management, they may also diversify farm income through production of timber or cordwood. Although introduction of honeylocust trees into pasture systems would be expected to be scale neutral (i.e. applicable across the range of farm sizes) their use may be of particular value for those farming small or hilly acreages where higher-value production systems are needed to improve small farm viability. Limited resource farmers such as those in Appalachia need management alternatives to help increase short- and long-term productivity of their land. 

Integrated tree-crop forage-livestock production systems may help make farms more diverse, productive, and sustainable, while minimizing adverse off-site environmental impacts. 
Because the Appalachian Region contains headwaters of most of the rivers that provide water for the major population centers of the eastern United States, it is critical that increases in the agricultural productivity of the region not compromise water quality. Incorporating honeylocust trees into pasture production systems may actually improve environmental health because trees protect stream quality and conserve soil fertility. Trees retain and recycle on-site nutrients because they are excellent scavengers of nutrients from the subsurface flow. In addition, leaf litter from trees adds organic matter to the soil, aiding soil aggregation and reducing nutrient run-off.

Our project focused on evaluating the productivity and nutritive value of honeylocust seed pods because data on nutritive characteristics of improved varieties of honeylocust (such as Millwood) are limited. Although utility for cattle may differ from that for sheep, honeylocust pods represent a potential high-quality feed resource for ruminants, and information on this resource is needed to help guide producer management decisions regarding tree selection and utilization within silvopastures. These efforts are part of a larger project to develop diverse, sustainable, and environmentally sound tree-crop and forage-livestock production systems for farms on marginal lands with limited resources.