MEASURING THE ENVIRONMENTAL-EFFECTS OF CONVERTING CROPLAND TO SHORT-ROTATION WOODY CROPS - A RESEARCH APPROACH

Conversion of cropland to short-rotation woody biomass crops (SRWC) ha s received increasing interest as biomass utilization technologies hav e improved and concerns for effects of fossil fuel emissions on global climate have developed. Effects of this conversion on erosion, hydrol ogy, water quality and soil productivity may be significant. A large c ooperative research project began in the spring of 1995 at three sites representative of the lower Tennessee Valley to compare the environme ntal effects of growing traditional row crops with the production of S RWCs over 3- to 5-year rotations. This paper presents the research app roach be used to evaluate these effects and a few preliminary results from the initial 3 months of the study. Small watersheds cultivated in row crops: corn (Zea mays L.) or cotton (Gossypium hirsutum L.), are being compared with small watersheds in tree crops: sycamore (Platanus occidentalis L.), sweetgun (Liquidambar styraciflua L.) or eastern co ttonwood (Populus deltoides Bartr.) with respect to: (1) erosion; (2) run-off quality (nutrients, pesticides) and quantity; (3) groundwater quality; (4) soil chemical changes (carbon, nutrients, pesticides); (5 ) soil physical changes (infiltration, bulk density, aggregate stabili ty); (6) soil biological changes; and (7) wildlife populations. During the spring and summer of the first growing season, few differences in run-off quantity and erosion were observed between treatments. One ex ception was a tendency towards higher erosion under cotton than cotton wood. Larger differences are expected in later years as trees become e stablished and a litter layer develops. At two sites during the first growing season. differences between row crops and SRWCs were observed in both the runoff and leaching of NO3-N, NH4-N, P, Ca, Mg and K in sp ring following fertilization of the row crops only at these two sites. Wildlife studies on small mammals and bird populations, as well as mi crofauna, are just getting under way. (C) 1998 Elsevier Science Ltd.