Temporal and Spatial Influences of Juglands nigra and Gleditsia triacanthos on Soil Indicators in a Southern Appalachian Silvopasture Study Area By Scott A. DeBruyne and Dr. James A Burger, Virginia Tech Blacksburg Virginia, and Charlie Dr. Charlie Feldhake, USDA ARS Results and Discussion Temporal Effects of Treatments Comparison of the relative concentrations carbon and the macronutrients from loose soil samples, was used as a means of normalizing the data due to apparent differences between the 2003 and samples. There was no significant difference in the concentration of carbon or macro nutrients between treatments. Assuming that there was no real change in the controls between the 2003 and the sampling, then, there were also no significant differences between years (Fig. 4). The average relative concentration, as compared to the average concentration of control in each year, of total nitrogen, potassium, carbon, copper and boron increased between the 2003 to the sampling, and may become significant with time. No significant differences in physical indicators were measured between treatments. A decrease in total bulk density, and increase in Macro porosity was observed between 2003 and , but this difference disappears once the data is normalized (Fig. 5). Spatial Effects Within Treatments There were no significant differences in ammonium, nitrate, or total nitrogen content between treatments or at different distances. Average values for honey locusts’ ammonium and total nitrogen values, and the walnuts’ total N values did tend to be higher than the control values (Fig. 6). No significant differences in bulk density or macro porosity were observed between plots, or at different distances. Though not significant, the honey locust and black walnut plots seem to have increased bulk density and decreased macro porosity as distance from the tree row increases (Fig. 5). Figure 4. Comparison of relative soil concentrations of macronutrient and carbon levels in all treatments from samples collected in 2003 and Figure 1. Kentland Farm Agroforestry Reasearch Center. The silvopasture study area is in the red oval. Figure 2. Sampling layout for the silvopasture. Samples were collected on a gradient from one tree row to the next. Sampling occurred within each tree row in each treatment at 5 slope positions for the loose soils and at 3 slope positions for the bulk density samples. Figure 3. Sheep grazing under J. nigra in one plot of the silvopasture in 2003 Figure 6. Normalized bulk density and macro porosity values of from the 2003 and sampling. Control and Black walnut values are offset to allow for easier viewing. Introduction Silvopastures have been recommended as method of increasing forage production while simultaneously improving soil quality and increasing carbon storage. Silvopastures may effect soil quality and have different soil properties than pastures without trees, with the degree of difference in the soil properties dependant on factors including tree species, forage species, soil type, silvopasture age, and the distance of the soil from the tree. The objectives of this research were: To determine the effect of black walnut (Juglans nigra L.) and honeylocust (Gleditsia triacanthos L.) orchardgrass/fescue silvopastures on nutrient soil quality indicators. To determine if soil indicators changed between the sampling of the site in 2003 (pre-livestock) and To determine how soil indicators change as a function of distance from tree. Materials and Methods Silvopastures are located at the Kentland farm agroforestry research center, located approximately 15 km from Blacksburg Virginia. The study area contains pasture plots with 10 year old honey locust, black walnut and open pasture. The site is composed of nine plots with three replications of the three treatments in a randomized block design (Fig. 1). Within each of the silvopasture treatments, the trees were planted in a 2.4 by 12.2 m (8 by 40 ft) spacing (fig. 2). Sampling was done in the spring of 2003 and the fall and winter of Loose soil samples were collected from the top 15 cm of soil at 5 distances between tree rows in each of 5 slope positions. Intact soil cores were collected from the top 10 cm of soil. The cores were used to measure macro-porosity, capillary- porosity, total porosity and bulk density. Total soil C and total N were determined using an Elementar CNS analyzer. NH4 and NO3 were determined by KCl extraction and spectroscopy. Other elements were extracted with Mehlich I and determined by ICP spectroscopy. Conclusions Though currently not significant, the honey locust appears to have had a positive effect on nutrient and soil carbon indicators. This is likely due to better nutrient capture and accumulation in the soil surface by the honey locust. The lack of a measurable influence of black walnut was not expected and could be due to the propensity of this species to be more deeply rooted compared to having a more dense lateral root network characteristic of the honey locust. As the silvopasture increases in age the treatment effects may become more pronounced. Acknowledgements We thank the U.S. Department of Agriculture Agricultural Research Station in Beaver, West Virginia for their funding and material aid in this research work.