Charles M. Feldhake

Soil spatial variability relationships in a steeply sloping acid soil environment

Management of pastures in steep terrain can be expensive in terms of time, chemical inputs, and equipment requirements. Management of those portions of pasture that will yield the most for minimum inputs requires a knowledge of the spatial patterns of the soil and atmospheric environments. A steep 2.4-ha unimproved pasture in southern West Virginia was studied to determine the spatial dependency of aboveground biomass production on soil characteristics. The predominant soil of the study site was Gilpin silt loam (fine-loamy, mixed, mesic, Typic Hapludults) with an average A-horizon pH (1:1 H 2 O) of 4.5 (range 3.8 to 6.1). The study site was broadcast seeded with red fescue (Festuca rubra L.) in 1982, making it the major plant species. However, several other plant species, including orchardgrass (Dactylis glomerata L.), red clover (Trifolium pratense L.), white clover (Trifolium repens L.), broomsedge (Adropogon virginicus L.), velvet grass (Holcus lanatus L.), yarrow (Achillea millefolium L.), and wild strawberry (Fragaria virginiana L.), and others were common. Transects were laid out up and down the north-facing, south-facing, and west-facing slopes and one transect was established on the contour for measurement of soil characteristics at a 1-m spacing. Plant aboveground biomass was measured at a 2-m spacing on three of the slope transects and on the contour transect. Although correlation analysis failed to find many statistically significant relationships between biomass production and soil characteristics, cross-semivariogram analyses of biomass production and surface soil pH and extractable Al, Mn, and P indicated that a strong spatial dependency exists. Those relationships were used for identifying homogeneous areas of biomass production and associated soil characteristics by ordinary kriging.

Microclimate of a natural pasture under planted Robinia pseudoacacia in central Appalachia, West Virginia

The conditions under which forages yield more under tree canopies than in open fields are not well understood. This study was conducted to determine how microclimate experienced by forages in central Appalachia is modified by black locust (Robinia pseudoacacia L.) tree canopies. The effect of tree row location relative to forage growing point was evaluated for its impact on soil water, photosynthetically active radiation (PAR), red/far-red ratio, and surface soil temperature. There was no consistent spatial dependency relating tree rows to soil water levels. While daily PAR decreased as the time under shade increased, the level of PAR under tree canopies nearly doubled as cloud cover increased from 0 to 25%. The red/far-red ratio decreased from 1.16 to 0.2 over forage growing between tree rows compared to forage within tree rows. Surface soil temperature remained nearly constant (1.5–2 °C increase) during sunny days under tree canopies but increased 8–12 °C by mid afternoon at unshaded sites depending on soil water levels. Forages under black locust trees experienced less extreme variation in both daily PAR and temperature than unshaded forages, thus reducing the metabolic cost of adaptation to extreme conditions.

Establishing trees in an Appalachian silvopasture: response to shelters, grass control, mulch, and fertilization

In order to successfully introduce trees into existing pastures, it is important to determine and recommend a whole range of tree establishment practices. In the spring of 1995, approximately 350 bare-root seedlings each of black walnut (Juglans nigra L.) and honeylocust (Gleditsia triacanthos L.) were planted in six randomized paddocks within a silvopastoral study area at the Agroforestry Research and Demonstration Site in Blacksburg, Virginia. Three seedling establishment studies were tested, including (1) a tree protection study, (2) a water retention study, and (3) a fertilization study. Seedlings were planted using two different tree shelters (60 cm-tall poultry wire cage and 1.2 m-tall plastic Tubex), two water retention treatments (mulch and herbicide spray), and one fertilizer treatment. All treatments were compared to untreated controls. Tree survival, damage, and stem volume were compared for each species. Tree survival was comparable among all studies over three growing seasons. Tree establishment using poultry wire and Tubex shelters resulted in significant reduction of deer damage and significant increase in stem volume from 1996 to 1998. Tubex shelters had a pronounced positive impact on tree height and also on stem form; height of both black walnut and honeylocust was twice the height of control seedlings. Mulch and herbicide treatments for moisture control resulted in significant stem volume increases over thecontrol treatment from 1997 to 1998. However, mulching was less effective than the herbicide treatment. There was no significant tree growth response resulting from fertilization during this same period.

Light Measurement Methods Related to Forage Yield in a Grazed Northern Conifer Silvopasture in the Appalachian Region of Eastern USA

The Appalachian region is characterized by hilly topography and a humid temperate climate. In most areas agriculture is limited to pasture although the native climax vegetation is a species-diverse forest. Silvopasture systems can help diversify and increase farm income. Information is needed on the yield response of forage grown as an understory crop among trees. The light environment of a conifer silvopasture was characterized by three methods, a hand-held photosynthetically active radiation (PAR) meter for quick measurements over a large area, fixed PAR meters recorded using data loggers for a large number of measurements over time, and hemispherical photography with software to calculate seasonal direct beam radiation. Light data were considered in terms of forage yield. Plots were harvested when forage reached 20–25 cm in height after which the entire area was grazed by sheep. There were limitations to all methods of quantifying radiation environment for predicting yield. Yield decreased linearly with decreased PAR; however, data variability was high and correlations, while statistically significant, were weak. Grazed silvopastures are dynamic with shifting yield patterns in response to the interactions between the spatially variable soil, changing seasonal environment, and spatially variable animal impacts for each grazing event.

Tree Establishment for a Temperate Agro-forest in Central Appalachia, USA

Small farms in Appalachia are economically challenged due to complex topography and soil constraints that limit productivity. Most farms have considerable acreage in forest, some of which is on the least productive sites, which contributes little income. The purpose of this study was to determine management and microclimate impacts on the establishment of an agro-forest for increasing the economic value of the forested land resource. A 1.2 ha forest clear-cut was planted with red oak (Quercus rubra) as the desired mature forest species alternated with rows of Chinese chestnut (Castanea mollissima), pawpaw (Asimina triloba), hazelnut (Corylus americana), and white pine (Pinus strobus) for generating income as the forest matures. Oak and chestnut required protection from deer. Oak had the lowest survival rate (61%) and chestnut had the highest survival rate (94%). While providing protection, Tubex plastic tubes also resulted in spindly tree growth. Plastic tubes did, however, improve pawpaw survival. Oak did best on well-drained locations. Chestnut and hazelnut were negatively impacted by forest edge more than oak or pawpaw. Overall there was a high degree of variability in tree growth suggesting that on low productivity sites, a planting density substantially higher than the desired final stand may be warranted to optimize the tree-vigor/micro-site match.

Forage Production Under and Adjacent to Robinia pseudoacacia in Central Appalachia, West Virginia

Species-diverse production systems, such as agroforestry, provide opportunities to increase the value of total production through marketing of multiple products from a given unit of land. Designing successful systems requires an understanding of how species compete for resources and grow in proximity to other species with distinctly different growth habits and resource demands (Sanchez, 1995; Ong and Leakey, 1999). Systems successful in a particular soil-climate environment may not be productive or sustainable in others (Ong et al. 1991). Soil fertility, texture, and depth along with temperature, timing and amount of precipitation, solar radiation levels, and topography provide a wide array of site conditions that generates a virtually continuous array of growing conditions. The Appalachian Region of the eastern United States is characterized by steep, complex topography and a humid, temperate climate. Agricultural production is mainly from small farms averaging 60 ha with 40% of that land area occupied by woodlands (USDA, 1999). Since the terrain is steep and fiscal resources limited in many cases, highly mechanized and chemical-dependent crop production is limited. The dominant form of agriculture, on an area basis, is the production of perennial forage grazed by beef cattle. This form of agriculture does not generate enough income to support a family on an average farm, thus off-farm jobs are the norm. Agricultural systems that offer some prospect of increasing income and providing environmental services are desirable. The Appalachian Region is economically depressed relative to most of the United States. The headwaters of most major river systems in the eastern United States are located in the region. Since these river systems provide water for many major population areas in the eastern United States, it is important that increased agricultural production is not achieved at the expense of water quality. One approach to improving small farm productivity is to implement silvopasture systems that provide treeand forage-based income-generating opportunities.

Calibration and use of plate meter regressions for pasture mass estimation in an Appalachian silvopasture

A plate meter for measuring pasture mass was calibrated at Agroforestry Research Site in Blacksburg, Virginia, USA, using six ungrazed plots of established tall fescue overseeded with orchardgrass. Each plot was interplanted with bare root honey locust and black walnut seedlings spaced along a gradient ranging from 1.8 to 11.0 m. Plate height (PH) of forage between trees was measured by placing a 46 mm × 46 mm × 5.6-mm-thick acrylic plastic plate meter on pasture canopy at six locations four times a season. PH was measured between ground and plate as it rested on pasture canopy. To calibrate the plate meter against a known dry matter yield, 50 × 50-cm clip plots followed each PH measurement. The resulting regression slope was 421 kg ha−1 cm−1, with an r 2 value of 0.86. Unique research investigating the response of forage mass to site elevation is presented using the developed equation. The field-calibrated regression slope of ruler height (RH) to PH was 1.71 cm cm−1, with an r 2 value of 0.87, showing good correlation between RH and PH. A comparable regional regression equation was found to adequately predict independent calibration clip plot data reported at this site. The results support the application of regression equations for estimating pasture mass in areas having similar climates and pasture composition.

Soil spatial variability and steep pasture management considerations in an acid soil environment

Management of pastures in steep terrain can be expensive in both time and equipment requirements. Management of those portions of pasture that will yield the most for minimum inputs requires a knowledge of the spatial patterns of the soil and atmospheric environments. A steep 2.4 ha unimproved pasture in southern West Virginia was studied to determine the spatial dependency of aboveground biomass production on soil characteristics. The predominant soil on the study site was Gilpin silt loam (fine-loamy, mixed mesic, Typic Hapludults) with an average A-horizon pH (1:1H2O) of 4.6 (range 3.8 to 6.1). Three transects were laid out up and down the slope and one transect on the contour for measurement of soil characteristics at a one meter spacing. Plant aboveground biomass was measured at a two meter spacing on three of the slope transects and the contour transect. Although correlation analysis failed to find any strong relationships between biomass production and soil characteristics, cross-semivariogram analyses of biomass production and surface soil pH and extractable Al, Mn, and P indicated that a strong spatial dependency existed. Those relationships were used for identifying homogeneous areas of biomass production and associated soil characteristics by ordinary kriging.