Tree growth and timber returns for an agroforestry trial in Goldsboro, North Carolina
Abstract
A 17 acre (6.9 ha) agroforestry research and extension alley cropping trial was established at the Center for Environmental Farming Systems in Goldsboro, North Carolina in January 2007, with a randomized block design with five replications. The demonstration planted rows of loblolly pine (Pinus taeda), longleaf pine (Pinus palustris), and cherrybark oak (Quercus pagoda), with crop lands in alleys of 40 ft or 80 ft (12.2 to 24.4 m) wide between the tree rows. Crops of soybeans (Glycine max) and corn (Zea mays) were planted in alternating years since establishment. As of 2011, survival rates were 93 [percent] for cherrybark oak, 88 [percent] for longleaf pine, and 97 [percent] for loblolly pine. Average diameter at ground level was 1.0 in (2.5 cm) for cherrybark oak, 2.1 in (5.3 cm) for longleaf, and 3.2 in (8.1 cm) for loblolly. Heights averaged 4.6 ft (1.4 m) for cherrybark oak, 5.2 ft (1.6 m) for longleaf, and 10.4 ft (3.2 m) for loblolly. Growth, yield, and economic projections for traditional timber production indicated that species volumes and values tracked the current height and diameter relationships. Loblolly pine had the largest projected internal rate of return, at 7.2 [percent], followed by longleaf pine at 3.5 [percent], and cherrybark oak at 2.9 [percent]. There might be more loss in crop and silvopasture production with loblolly, however, and production of pine straw for longleaf or game mast for cherrybark oak may offer other benefits. Crop yields on the sandy soils were very poor during the four years observed.