Measuring the environmental effects of converting cropland to short-rotation woody crops: A research approach

Abstract

Conversion of cropland to short-rotation woody biomass crops (SRWC) has received increasing interest as biomass utilization technologies have improved and concerns for effects of fossil fuel emissions on global climate have developed. Effects of this conversion on erosion, hydrology, water quality and soil productivity may be significant. A large cooperative research project began in the spring of 1995 at three sites representative of the lower Tennessee Valley to compare the environmental effects of growing traditional row crops with the production of SRWCs over 3- to 5-year rotations. This paper presents the research approach 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.), sweetgum ( Liquidambar styraciflua L.) or eastern cottonwood ( 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 stability); (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 exception was a tendency towards higher erosion under cotton than cottonwood. Larger differences are expected in later years as trees become established 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 NO 3-N, NH 4-N, P, Ca, Mg and K in spring following fertilization of the row crops only at these two sites. Wildlife studies on small mammals and bird populations, as well as microfauna, are just getting under way.