http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Microbial activity as a tool for assessing agricultural soil
xiii, 143 leaves : illustrations ; 28 cm.
A rapid soil testing procedure for soil C and N mineralization that is both rapid and precise is needed. The rapid procedure is based on the quantity of CO₂-C evolved for 24 hours under optimum laboratory conditions following the rewetting of dried soil and is strongly correlated with N mineralization. Results of the one-day CO₂ procedure were highly correlated with soil N mineralized from samples collected in March for 1995 and 1996 (p=0.004, p<0.001) and forage N uptake (p<0.001) for both years of the study near Stephenville, Texas. Residual inorganic N in the same soil samples was poorly correlated with soil N mineralization and forage N uptake. Herbicides applied to soils potentially affect soil microbial activity. The objective of this study was to determine the impact of glyphosate on soil microbial biomass and activity across a wide range of soils. Glyphosate significantly stimulated soil microbial activity as measured by C and N mineralization, as well as soil microbial biomass. Strong linear relationships between C and N mineralized, as well as between soil microbial C and N (r² = 0.96, 0.95), respectively. Glyphosate appeared to be rapidly degraded by soil microbes regardless of soil type or organic matter content, even at high application rates, without adversely affecting microbial activity. Methods of determining soil microbial biomass need to be reliable and produce consistent results across soils with a wide range of properties. Extraction efficiency of 0.5 M K₂SO₄ relative to water was dependent upon soil pH. Changes in microbial biomass estimates with changes in extractant molarity and soil pH suggest that chloroform fumigation-extraction may not be reliable in a wide range of soils.
Issued also on microfiche from University Microfilm Inc.
Includes bibliographical references (leaves 129-142).