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United States Department of Agriculture

Agricultural Research Service

2008 Annual Report

1a.Objectives (from AD-416)
Enhance carbon sequestration for improved soil quality and erosion control; Quantify the form and release of major nutrients as affected by soil redox potential; Determine the impacts of conservation tillage on fate of pesticide in soil.

1b.Approach (from AD-416)
Quantify dissolved organic carbon in runoff samples from subwatersheds in the St. Joseph River; Identify enzymes as soil quality indicators; Monitor effects of changing soil redox potential on nutrient form and release; Quantify the fate of atrazine, metolachlor and glyphosate under varying temperature and crop residue; Quantify the competition between glyphosate and phosphorus and glyphosate and potassium for possible nutrient decline due to glyphosate usage.

3.Progress Report
• Monitoring of dissolved carbon losses from runoff and subsurface tile drainage at twelve sites within the Cedar Creek watershed was continued in FY08. This work is in tandem with the National Soil Erosion Research Laboratory’s Conservation Effects Assessment Project (CEAP) water quality project. Data from the first five years are being analyzed for publication. • Four additional ARS Experimental Watersheds were sampled for soil sequestration and soil quality (Cedar Creek in IN, Beasley in MS, Choptank in MD, and UNH in NH). Soils have been processed and are being analyzed in cooperation with the National Soil Tilth Lab (Ames, IA). Analyses for three of the first five watersheds (Southfork and Walnut Creek in IA and Leon River in TX) have been completed, with the remaining two scheduled for completion by the end of the calendar year (Little River in GA and Ft. Cobb in OK). • The scientific literature has been reviewed for linkages between ß-glucosidase activity and soil quality and carbon sequestration. ß-glucosidase is involved in the decomposition of plant residues and roots. Additionally, a ß-glucosidase indicator has been developed for inclusion into the Soil Management Assessment Framework (SMAF). A draft of a paper describing this work has been completed. • Monitoring of trace gas emissions and carbon sequestration continues at two experimental sites: ACRE, west of West Lafayette, a Mollisol soil and TPAC, south of Lafayette, an Alfisol soil. Both sites include corn-soybean rotations (five treatments) and ACRE includes grass management plots. Data from the first four years of measurement are being analyzed for publication, with one manuscript submitted for publication and another scheduled for completion by the end of the calendar year. Based on the results, treatments were reviewed and alterations were made at both sites. • Monitoring of changes to soil quality characteristics, carbon sequestration and productivity is continuing in the field experiment designed to determine impacts of corn residue removal on the soil. We are also following changes in soil biochemistry (soil enzyme activity) over time. • A constant temperature room was constructed to conduct the redox experiments and collect data on nutrient form and release. Experiments have been conducted using the redox instrumentation developed earlier at the National Soil Erosion Research Laboratory, but modified for this study. Data are presently being analyzed. • A green house protocol for adjusting redox potential was developed and bench top experiments are being conducted. Field plots with different rates of gypsum were completed and a newer one established to expand to include heavy metal uptake in plants. • Plans are being developed for an incubation study to explore the impact of glyphosate application rates on the form and release of soil P and K.

This accomplishment supports NP 202, Component 2.

1. Development of an early indicator of soil carbon sequestration trends. A review of the peer-reviewed literature, as well as data from on-going experiments, on soil enzyme activity showed that ß-glucosidase activity, when normalized to soil carbon content indicated the likely trend in soil carbon sequestration. This value, calculated as ß-glucosidase activity (reported as µg p-nitrophenol released g-1 soil hr-1 incubation) divided by the soil carbon content (g C kg-1 soil) (BGN), for sites with native vegetation, long-term pastures, and some no-till systems fell between 11-16. High BGN values indicate systems that will likely sequster C in the future. Low BGN values (< 11) indicate management systems that will result in degradation of the soil. The BGN value is an early indicator of the impcat of soil management systems on C sequestration and overall soil quality. The impact is that now there is a way to determine if changes to a managment system are going to result in soil carbon stocks changes without having to wait 3-5 years or longer before current analytical techniques can detect changes in soil C. This accomplishment supports NP 202 Problem Statement 3.2 Soil Carbon Dynamics.

2. Development of B-glucosidase indicator scoring curves for the Soil Management Assessment Framework (SMAF). SMAF, the leading soil quality model, does not yet include any soil enzyme as an indicator of soil quality or function. Work was completed to develop a set of scoring curves and the accompanying algorithms that take into consideration soil type, based on the ability of a soil to sequester carbon, soil texture and local climate. This expands the usefulness of the SMAF model, which is beginning to be widely used to access management impacts on soil quality. The accomplishment supports NP 202 Problem Statement 5.2. Decision tools to assess benefits and enhance adoption of conservation practices and systems.

6.Technology Transfer

Number of Non-Peer Reviewed Presentations and Proceedings1

Last Modified: 10/7/2015
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