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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOGEOCHEMICAL PROCESSES INFLUENCING FORMATION AND STABILIZATION OF SOIL ORGANIC MATTER AND SOIL STRUCTURE
2010 Annual Report


1a.Objectives (from AD-416)
1)Develop a mechanistic understanding of processes controlling the formation and stabilization of organic matter in soils that enhance stabilization of soil structure. a) Determine the relative contributions of biochemical compounds to aggregation and C sequestration. b) Determine the role of clay minerals and charcoal in the formation and stabilization of soil organic matter and soil structure. c) Determine the nature of reactions between smectites and pesticides. d) Determine the effects of anaerobic soil conditions on biochemical processes that influence soil nutrient cycling. e) Develop integrative methods for fractionating SOM into meaningful pools..
2)Develop tools for in situ assessment of soil organic carbon and soil structure. a) Develop a multi-function probe (electrical and thermal properties) to evaluate soil structure. b) Develop and evaluate a field mobile NIRS tool for sensing soil carbon and various soil properties.


1b.Approach (from AD-416)
Field plot and column leaching studies will be used to quantify the impact of adding charcoal to soils on nutrient cycling, soil productivity, C sequestration, pesticide leaching, and on the formation and stabilization of clay-humic complexes. Interactions between selected pesticides and reference clays will be investigated to elucidate bonding mechanisms between organic molecules and clay surfaces. Seasonal patterns for cycling of phenolic and organic nitrogen compounds will be compared for routinely flooded and non-flooded soils. Anticipated products will include more accurate predictions of how crop and soil management effect nutrient cycling and soil organic matter stabilization. We will develop and test electrical and thermal soil probes to characterize soil structure. A regional non-linear multivariate calibration model for a recently developed on-the-go in situ near infrared diffuse reflectance soil probe will be evaluated to determine if the system can accurately map the spatial distribution of numerous soil properties (organic C, total N, CEC, moisture, buffer pH, and extractable nutrients) at the field scale.


3.Progress Report
Progress during fiscal year 2010 (FY10) in soil biochar research includes both field and lab scale work. Second year plant population and yield data for biochar plots established in 2007 showed no significant effect of biochar on plant populations. Several years of field data will be required before definitive information on the impact of biochar on soil quality, crop yields, and carbon sequestration can be determined. Biochar plots established in the Fall of 2008 are evaluating the impact of interactions between manure and biochar on soil quality and crop productivity. First year data showed no significant differences in yield or plant populations due to biochar additions. First year crop yields were low for all plots due to nitrogen deficiency. Statistical analysis of data from the 500-day biochar column study was completed, two manuscripts from this study were published in FY10, and a third has been submitted for publication. 13C-label corn stover was produced and will be used to quantify the interactions between biochar, residue, and soil organic matter. Collaborative germination and early plant growth studies indicate that high-temperature biochars may contain compounds that inhibit early growth of corn seedlings and some prairie species. Field studies designed to develop sustainable management strategies for harvesting corn stover as a biofuel feedstock continued at four locations. At the Bruner farm where stover removal has been on-going since 2005, the “lower half by height” treatment was changed to a “cobs only” treatment for the 2009 field harvest. The quantity of biomass removed remained about the same (~1.8 Mg ha-1), but feedstock quality was substantially better. Soil analyses are being used to track soil quality impacts using Soil Management Assessment Framework (SMAF). Data from 2008 showed that higher plant populations (~106,000 plants ha-1) planted in twin-rows increase yield, but not in 2009, possibly due to a high degree of cloudiness during July and August. Seeding a rye cover crop three weeks before grain harvest provided surface cover during the winter and good seedbed conditions for the subsequent corn crop. These studies contribute to the Agricultural Research Service (ARS) Renewable Energy Assessment Project (REAP) project. A published analytical method for carbohydrates was found to include two pairs of mis-identified compounds; a correction for this method was developed. A new more rapid analytical method for phenols in soil organic matter is under development. Plant and soil samples were collected, processed, and analyzed for the final year of field evaluations of rice grown on furrow-irrigated raised beds and paddy rice subjected to field drainage at key stages of crop growth. A humic product is being evaluated for the impact on corn growth. Crop growth measurements were taken at one field experiment on a research station and in three local farmers’ fields. The humic product increased corn ear size and expanded the grain-filling period by 10%. Grain yield was measured by hand and combine at the research station, in two of the three local farmers’ fields, and in 30 more farmers’ fields in other areas of Iowa.


4.Accomplishments
1. Biochar, a form of charcoal produced while making renewable biofuels, can be used to increase carbon storage and improve soil quality in Midwestern fields. Agricultural Research Service (ARS) scientists in Ames, Iowa, conducted laboratory and field studies to determine how biochar affected several soil biological, chemical, and physical properties in a typical agricultural soil. The laboratory study showed that applying biochar decreased soil compaction, increased soil acidification (pH), and increased the capacity of soil to hold water and plant nutrients compared to soils that did not receive biochar. Applying biochar increased total nitrogen by as much as 7%, organic carbon (C) by as much as up to 69%, and the quantity of several other plant nutrients compared to the unamended soil. These results are important because in addition to helping produce renewable bioenergy, the process that creates biochar (pyrolysis) also produces a co-product that can be used to store soil carbon and improve other soil properties and processes (i.e., soil quality).

2. Using the Soil Management Assessment Framework (SMAF) can help quantify long-term effects of harvesting corn stover or other crop residues. ARS scientists in Ames, Iowa, used a SMAF analysis to establish baseline against which effects of harvesting corn stover as a bioenergy feedstock can be evaluated. The analysis showed that total organic carbon, soil-test phosphorous, and soil bulk density had the lowest values and therefore needed to be closely monitored. No-tillage increased soil carbon concentrations, but the overall soil quality index decreased slightly under no-tillage because of lower acidification (pH) and higher bulk density (compaction).

3. Soil organic matter is a complex material that can be better characterized by using a combined physical and chemical extraction procedure than either method alone. The physical extraction involves either sieving or floating the lighter weight organic material away from the heavier soil mineral particles. Various chemical analyses are then used to determine the composition of the various fractions. ARS scientists in Ames, Iowa, used sequential steps of sieving, floating, and chemical extraction to characterize soil organic matter from soils under different management practices and showed that the fractions have different chemical properties. This is important because more complete analysis of soil organic matter is crucial when investigating soil carbon sequestration (storage), nutrient cycling (fertility), and soil aggregation (structure).


Review Publications
Logsdon, S.D., Green, T.R., Seyfried, M.S., Evett, S.R., Bonta, J.V. 2010. Hydra Probe and Twelve-wire Probe Comparisons in Fluids and Soil Cores. Soil Science Society of America Journal. 74:5-12.

Zobeck, T.M., Norfleet, M.L., Karlen, D.L. 2009. Soil Conditioning Index. In: Lal, R. Encyclopedia of Soil Science. Second Edition. New York, NY: Taylor & Francis Group. Available: http://www.informaworld.com/10.1081/E-ESS-120044014.

Wienhold, B.J., Karlen, D.L., Andrews, S.S., Stott, D.E. 2009. Protocol for indicator scoring in the soil management assessment framework (SMAF). Renewable Agriculture and Food System. 24(4):260-266.

Amer, A.M., Logsdon, S.D., Davis, D. 2009. Prediction of Hydraulic Conductivity as Related to Pore Size Distribution in Unsaturated Soils. Soil Science. 174(9):508-515.

Kovar, J.L., Pierzynski, G.M. 2009. Methods of Phosphorus Analysis for Soils, Sediments, Residuals, and Waters-Revised Edition. Southern Cooperative Series Bulletin. Available: http://www.sera17.ext.vt.edu/Documents/P_Methods2ndEdition2009.pdf

Logsdon, S.D., Schilling, K.E., Hernandez Ramirez, G., Prueger, J.H., Hatfield, J.L., Sauer, T.J. 2010. Field estimation of specific yield in a Central Iowa crop field. Hydrological Processes. 24(10):1369-1377.

Last Modified: 11/24/2014
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