Soil and Water Quality Research Unit

Welcome to the Soil and Water Quality Unit web site.   This unit is part of the National Soil Tilth Laboratory.

Dr. Douglas Karlen

Research Leader

2110 University Boulevard

Ames, IA  50011

Soil and Water Quality Unit Research Programs
Biogeochemical Processes Influencing Soil Structure and Organic Carbon Sequestration

(1) Identify mechanisms influencing retention of carbon in soil to reduce increases of greenhouse gases in the atmosphere, including formation of organic C stable aggregates and C sequestration in soils.  (2)  Determine relationships between microbial and plant processes and the impact on processes that regulate the exchange of greenhouse gases between soil and the atmosphere, including C sequestration, C and N mineralization, and aggregation.  (3)  Determine the complex permittivity spectra and electrical conductivity of soil water and use these to evaluate soil structure and its possible impact on processes affecting greenhouse gas fluxes.  (4) Quantify the effect of long-term management on removal of carbon from the atmosphere and storage in the soil, and on soil structure that may affect movement of carbon among soil, water, and atmospheric pools.

Assessing and Using Soil Quality to Guide Sustainable Land Management Objectives

(1) Determine how soil management practices affect sensitivity and response of various soil quality indicators; (2) Improve N and P use efficiency through use of appropriate soil quality indicators; (3) Describe persistence, bioavailability and transport of organic chemicals relative to soil quality assessments; (4) Develop soil quality assessment methodology for field, watershed, and regional scales.

Reducing Nitrate Contamination to Surface Waters from Artificially Drained Soils

(1)  Quantify at the watershed scale the impact of adopting the Late Spring Nitrogen Test to determine N fertilization of corn on NO3 concentration and load in subsurface drainage; (2)  Determine the temporal dynamics of soil N mineralization and evaluate the relationships between net N mineralization and soil microbial activity, organic matter pools, soil properties, and climate variables;  (3) Develop alternative tile drain design and management scenarios and evaluate the effectiveness on NO3 removal rate and capacity in poorly drained soils; and (4)  Modify and evaluate the ARS SWAT watershed model for simulating hydrology and water quality in tile drained watersheds.