CROP RESIDUE EFFECTS ON SOIL QUALITY FOLLOWING 10-YEARS OF NO-TILL CORN

Numerous biological, chemical, and physical indicators of soil quality have been suggested, but few have been evaluated using data from long-term field studies. Our objective was to evaluate several proposed soil quality indicators to determine effects of removing, doubling, or maintaining crop residues for 10 years in a no-till, continuous corn (Zea mays L.) production study. Soil aggregate characteristics, penetration resistance, bulk density, volumetric water content, earthworm populations, respiration, microbial biomass, ergosterol concentrations, and several soil-test parameters (pH, P, K, Ca, Mg, Total-N, Total-C, NH4-N, and NO3-N) were measured on samples collected from Rozetta and Palsgrove silt loam (fine-silty, mixed, mesic Typic Hapludalfs) soils. Soil aggregates from double residue treatments were more stable in water than those from normal and removal treatments. The double and normal residue treatments had higher total carbon concentrations and higher levels of microbial activity as measured by CO2 evolution. Ergosterol concentrations where crop residues were removed were 8 to 10 times lower suggesting this biochemical measurement of fungal biomass may be a sensitive soil quality indicator. Earthworm populations where crop residues had been removed for 10 years were significantly lower than in either normal or double residue treatments. Measures of force and energy required to crush soil aggregates were extremely variable and showed significant differences only for aggregate size. Several parameters were used to develop a soil quality index that gave ratings of 0.45, 0.68, or 0.86 for removal, normal, or double residue treatments,