Influence of solar radiation on the productivity and nutritive value of herbage of cool-season species of an understorey sward in a mature conifer woodland

Silvopastoral systems in the Appalachian region of the USA could increase the carrying capacity of livestock and contribute to a reliable supply of high-quality herbage. In 2000, 2001 and 2002, the influence of solar radiation [0.20, 0.50 or 0.80 of maximum solar radiation (MSR); treatments 20-, 50- and 80-MSR respectively] on the productivity and nutritive value of a mixture of sown grasses and legumes established under a mature stand of conifers was investigated. Yields of dry matter (DM), crude protein (CP), total non-structural carbohydrates (TNC) and total digestible nutrients (TDN) were greater for the 80-MSR treatment except in 2000 when DM yield did not differ. As a proportion of the sward, introduced species (Dactylis glomerata L., Trifolium repens L., and Lolium perenne L.) increased over time for the MSR-80 treatment, corresponding with a decrease in the proportion of bare area and of non-introduced species. CP concentration of herbage was 207 g kg(-1) DM or greater across treatments and years with higher concentrations on the 20- and 50-MSR treatments. Herbage from the 80-MSR treatment had a greater concentration of TNC than that of the 20- and 50-MSR treatments. Estimated concentration of TDN was similar for all treatments in 2000 and greater for the 80-MSR treatment than the other two treatments in 2001 and 2002. High CP concentrations in herbage, as a result of appropriate thinning of trees in an Appalachian silvopastoral systems, could be utilized as a protein supplement to herbage with low CP and higher fibre concentrations.