Water-budget evaluation of prairie and maize ecosystems

Annual monitoring of water-budget components is useful for comparing the fate of water inputs among ecosystems. Land-use changes from natural prairies to managed agroecosystems alter water-budget components. Weekly hydrological budgets for a restored natural prairie and maize (Zen mays L,) agroecosystems (no-tillage and chisel-plow) were constructed for 132 consecutive wk between June 1995 and January 1998. Precipitation, drainage, soil water-storage changes, and snow-cover changes were measured on Piano silt loam soil (fine-silty, mixed, superactive, mesic Typic Argiudoll) at agricultural and prairie sites. Compared with the maize ecosystems, the prairie maintained greater soil water contents deeper in the soil profile (0.8-1.4 m), somewhat larger evapotranspiration (Et), and significantly less drainage because of considerable interception of precipitation by a residue layer. Soil water storage in the no-tillage maize setting was more similar to the prairie, while Et, net primary productivity, and drainage were more comparable to the chisel-plow agroecosystem. Total drainage measured with equilibrium-tension lysimeters was 199 mm of water (coefficient of variation [CV] = 5.7%) for the prairie ecosystem, 563 mm of water (CV = 13.6%) for the no-tillage maize ecosystem, and 793 mm of water (CV = 18.5%) for the chisel-plow maize ecosystem. Residue interception for the prairie was 477 mm, compared with 681 mm of precipitation during the growing season of 1997, which contributed to lower prairie drainage. The combination of similar productivity, higher soil water contents, and less drainage than the chisel-plow ecosystem suggests that a no-tillage ecosystem is more sustainable than the chisel-plow agroecosystem in terms of reducing potential adverse environmental impacts associated with soil water movement.