2008 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.
Laboratory and field studies are in progress to determine the effects of biochar (charcoal derived from biomass) on soil properties, agricultural productivity, water quality, and carbon sequestering. Biochar was applied on 24 plots at two rates (9814 and 18440 kilograms per hectare (kg/ha)). The impact of these biochar applications on yields of continuous corn will be monitored over the next few years. A 500-day soil column study designed to quantify the impact of biochar on soil quality, carbon sequestration, emissions of greenhouse gasses and nutrient concentrations in leachate from the columns was completed. Analysis of the samples is nearly complete. Preliminary analysis of the data indicates that biochar amendments reduced soil bulk density, sequestered large amounts of carbon, increased soil respiration, reduced leaching of nitrate by 10%, and reduced phosphorous leaching by 40 to 70%. The biochar also acted as a liming agent.
Data analysis was completed and a paper written and submitted for publication documenting the interaction between cation exchange selectivity and adsorption of an organic compound (m-dinitrobenzene) by clay minerals. Results indicate that organic molecules on clay surfaces influence the affinity of the clay for various cations and conversely the type of cation on the clay surfaces influences the affinity of the clay for organic molecules through a complex feed-back system.
Work on testing the near-infrared tools for analyzing the spatial distribution of soil properties at a field scale was minimal this year. This effort has been deemphisized to make room for more biochar work.
New analytical tools for the analysis of amino acids and amino sugars, phenolic acids, and carbohydrates in soils are essential for meeting Objectives 1A and 1D. A relatively new analysis for amino acids and amino sugars was critically evaluated and modified to improve efficiency of extraction and quantification of these amino compounds. This method will allow scientists to study nitrogen cycling in soil and better predict nitrogen availability in soil for plant uptake. A method for measuring labile phenols was evaluated and found unsatisfactory. A replacement method for labile phenols is being set up, as is a method for ergosterol, which is a marker for fungal residues. A method for carbohydrates was set up.
Work is continuing on development of electrical and thermal probes to analyze soil structure. Preliminary experiments are being conducted to assess a commercial Hydra, monofunction thermal, and 12-wire probes using a vector network analyzer. Analysis of data collected with mono-function probes is underway. We have finished analysis from an Iowa prairie site, Idaho, Colorado, Ohio, and are working on samples from Iowa forest vs. crop. We received undisturbed cores from Texas but were unable to use them because of excess compaction. A multi-function probe will be built and tested in the future.
(NP202, Components 2, 4, and 7)
Laboratory versus field calibration of a soil moisture probe. Environmental and crop growth models require accurate soil moisture data which must be collected in the field with soil moisture probes. This study showed that soil moisture probes that were calibrated in the laboratory and then taken to the field do not give the same results as soil moisture probes that were calibrated on-site in the field. The laboratory calibration was linear, but the field calibration was non-linear perhaps due to uneven wetting of soils in the field. The study will help modelers to obtain more reliable soil moisture data and thereby to improve the accuracy of model predictions. (NP202, Component 2)
Electrical spectra of undisturbed soil from crop rotation study. Electrical spectra of soils can potentially be used to assess management effects on soil properties, but techniques for measuring electrical spectra of undisturbed soils are needed. A 12-wire probe for measuring electrical spectra of soils was developed and tested using undisturbed soil cores. Crop management did not have a significant effect on the electrical spectra, but soil differences were significant. Now undisturbed soil samples can be used for determining electrical spectra. (NP202, Component 2)
Soil moisture probes for dispersive soils. Soils with large amounts of high charge clays are electrically dispersive. This can cause erroneous readings with soil moisture probes that function at low frequencies unless they are specifically-calibrated on-site. Five different soil moisture probes were compared on dispersive soils. The two probes operating at the lowest frequency did not produce usable data on these soils. The other three moisture probes, which operate at higher frequency, worked well when calibrated on-site; however, the probe with the largest measurement volume produced the most consistent data. More reliable soil moisture data can be obtained on dispersive soils using soil moisture probes designed to operate at higher frequency. (NP202, Component 2)
Interaction between cation exchange selectivity and sorption of organic molecules by smectites. Little is known about interactions between organic molecules, cations, and clays in soil environment. Sorption of an organic molecule (m-dinitrobenzine) on smectite was shown to increase the preference of the clay for a weakly hydrated cation (potassium) relative to a strongly hydrated cation (calcium) and at the same time sorption of potassium on the clay was shown to increase the affinity of the clay for the organic molecule. A complex feed-back model was developed to describe these interactions. Scientists will be able to more accurately predict the fate of organic pollutants in soils and the ability of soils to supply nutrients to growing plants by better understanding interactions between organic and inorganic components of soils. (NP202, Component 7)
Improved understanding of organic nitrogen cycling in rice soils enabled improved nitrogen fertilizer recommendations. Continuous rice production in the Grand Prairie region of Arkansas has suffered from a substantial (~19%) reduction in grain yield compared to rice rotated with soybean. Research attributed this yield loss to a deficiency of plant uptake of nitrogen in the middle of the growing season. This was due to decreased plant uptake of nitrogen derived from soil organic matter, while plant uptake of fertilizer nitrogen was less affected. Acquired knowledge demonstrated that grain yield of continuous rice can be increased by adding more nitrogen fertilizer during the growing season as compensation for the decreased availability of soil organic nitrogen. This recommendation is being shared with and adopted by farmers and is expected to increase rice yields. (NP202, Component 4)
|Number of Non-Peer Reviewed Presentations and Proceedings||2|
Yamada, T., Logsdon, S.D., Tomer, M.D., Burkart, M.R. 2007. Groundwater nitrate following installation of a vegetated riparian buffer. Science of the Total Environment. 385(1-3):297-309.
Pereira, T.R., Laird, D.A., Johnston, C., Teppen, B., Li, H., Boyd, S. 2007. Mechanism of dinitrophenol herbicide sorption by smectites in aqueous suspensions at varying pH. Soil Science Society of America Journal. 71:1476-1481.
Logsdon, S.D. 2008. Electrical spectra of undisturbed soil from a crop rotation study. Soil Science Society of America Journal. 72:11-15.
Pereira, T.R., Laird, D.A., Thompson, M., Johnston, C.T., Li, H., Teppen, B., Boyd, S. 2008. Role of Smectite Quasicrystal Dynamics in Adsorption of Dinitrophenol. Soil Science Society of America Journal. 72:347-354.
Laird, D.A. 2008. The Charcoal Vision: A Win-Win-Win Scenario for Simultaneously Producing Bioenergy, Permanently Sequestering Carbon, While Improving Soil and Water Quality. Agronomy Journal. 100:178-181.
Laird, D.A., Chappell, M., Martens, D.A., Wershaw, R., Thompson, M. 2008. Distinguishing Black Carbon from Biogenic Humic Substances in Soil Clay Fractions. Geoderma. 143:115-122.
Singer, J.W., Logsdon, S.D., Meek, D.W. 2008. Soybean Growth and Seed Yield Response to Tillage and Compost. Agronomy Journal. 100:1039-1046.
Mao, J.D., Zhang, T., Lan, Y., Olk, D.C., Ding, G., Ceballos, M. 2008. Chemical Structures of Feces from Conventional and Phytase Transgenic Pigs Investigated by Advanced Solid-State NMR Spectroscopy. Journal of Agricultural and Food Chemistry. 56(6):2131-2138.
Logsdon, S.D. 2008. Activation energies and temperature effects from electrical spectra of soil. Soil Science. 173:359-367.
Laird, D.A. Analysis of Layer Charge, Cation and Anion Exchange Capacities, and Synthesis of Reduced Charge Clays. 2008. In: Ulery, A., Drees, R. editors. Methods of Soil Analysis, Part 5, Mineralogical Methods. Madison, WI. SSSA Book Serv. 5. SSSA. p. 485-508.