Species trials for biomass production on abandoned farmland.

As part of a nationwide study of the potential for woody crops to supply biomass for energy use, we evaluated seven hardwood tree species and six hybrid poplar clones on four different sites in Vermont, with three fertilizer treatments on some sites. Not all species were evaluated on all sites. Plots containing 25 trees were replicated three or four times at each site. Trees were planted at a spacing of 0.6 x 0.6 m or 0.9 x 0.9 m and grown for 3 years. The application of fertilizer did have significant effect on height, diameter, and stem weight. Species with high yields (about 16 oven-dry t/ha/year) included four of the hybrid poplars. Silver maple, black locust, and the other two hybrid poplars yielded about 10 oven-dry t/ha/year. Based on growth alone, these species and clones were recommended for short-rotation intensive culture in areas with similar climate and growing sites. North J. App!. For. 2:43-47, June 1985. The contributions of the following people to this project are gratefully acknowledged: S. H. Williams, J. A. Peterson, N. E. Scar-borough, L. A. Wilbur, K. Richards, D. B. Howard, G. J. Badger, and A. H. Rye. Acknowledgment is also made of support and coopera t ion f rom the following: Windsor Minerals Corporation; the Burl ington Elec tric Department; Vermont Department of Forests, Parks a n d R e c r e a t i o n ; a n d t h e M i n e r Agricultural Research Institute. Funded in part by the U.S. Department of Energy t h r o u g h O a k R i d g e N a t i o n a l L a b oratory. The potent ia l for increasing yields through short-rotation intensive culture (SRIC) of hardwood t rees has been recognized as a source of energy and wood fiber (USDA For . Serv . 1980). Hardwoods are favored for their ability to coppice, avoiding replanting cost after harvest. They are also capable of fast juvenile growth and grow over a geographically widespread area. The Shor t Ro ta t ion Woody Crop Program, sponsored by the U .S . Department of Energy and managed by Oak Ridge National Laboratory, consists of a number of projects nationw i d e w h i c h address a l l a s p e c t s o f SRIC, inc lud ing spec ies se lec t ion ; stand establishment and management; and co l l ec t i on , transportation, a n d storage strategies (Ranney et al. 1982). Several projects , including work re ported here, involve species selection. H a r d w o o d s p e c i e s o f t h e n o r t h eastern U.S. include several with possible value for SRIC. Work with hybrid pop la r has shown p rom i s e f o r f a s t growth and high yields (Dawson et al. 1976, Zsuffa et al. 1977, Dickmann and Stuart 1983). However, other species remained untested, especially in SRIC plantations. New England, because of changing METHODS To evaluate growth rate and yield on several s i tes , p lant ings were estab lished at four locations in Vermont in 1979, at elevations from 30 to 140 m and on different soils (Table 1). Seven species and six hybrid poplar clones were evaluated (Table 2). All planting sites were clean cultivated using a combinat ion of herbicides, plowing, harrowing, and rototilling (Hansen et al. 1983). Species p lots of 25 t rees , 5 rows x 5 t rees , were planted. A 3-year rotation was chosen with 0.6 x 0.6 m or 0.9 x 0.9 m spacing to obtain canopy closure in that t ime per iod. Species were ran domly planted within blocks. One or two rows of buffer trees were planted around each block. Blocks were repli cated three or four times, as space and stock availability permitted. Experi ment 3, site 3, had only one replicate because of unavailability of planting stock. Experiment 1 tested the effects of different rates of fertilizer application confounded with methods of application on tree growth rates and yield. A soil analysis determined the fertilizat ion rate for corn for each of three sites. All plots were fertilized to this control level. In addition, two other agricultural methods a n d d e c l i n i n g numbers of farms, contains large areas of land that were once farmed. For example, in Vermont in 1964 there were 9247 farms on 1.0 million ha; in 1979 there were 5900 farms on 0.7 million ha. Much of this abandoned marginal farmland is suitable for SRIC plantations. Our object ive was to tes t several hardwood species at close spacing in small plots on several sites to determine the species' potential for SRIC