Welcome to the Crop and Soil Sciences Seminar Series. Following is a list of the scheduled seminars for the 2006-07 academic year. Unless otherwise noted, all seminars are on Thursday, from 12:20 PM to 1:10 PM in 135 Emerson Hall. Please contact Lin Marco (lm69) or 5-1410 to reserve a slot.

Crop and Soil Sciences

SPRING 2007

5/24/07 - Computational Approaches to N Fertilizer Management Related to N2O Emissions and Economic Tradeoffs (Ivy Tan, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: Greenhouse gas (GHG) emissions from nitrous oxide (N2O) are due in part to N inputs on agricultural land.  This research examined the effects of management practices on N2O losses as a result of late-spring precipitation from both the experimental and modeling approach.  The Precision Nitrogen Management (PNM) model was calibrated using field data on N2O emissions, and soil physical and chemical properties collected from the experiment.  The PNM model was also used to simulate long-term net revenue from N fertilizer application to approximate average private and social returns for maize grain production under different N treatments. 

5/17/07 - Soil Nutrient Depletion and Repletion in the Tropical Highland Agroecosystems of Kenya (Solomon Ngoze, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: Soil nutrient depletion is a major challenge to agricultural productivity and economic growth in many developing economies in sub-Saharan Africa. Despite the general recognition of the impact of soil nutrient depletion on agricultural productivity, few studies have been undertaken to quantify the scope, rate and progression of depletion as a result of long-term human intervention (up to 100 years) in the region. This seminar will present findings on research topics that address: (1) assessment of impacts of household land use and socio economic factors in the highlands of Kenya. The objective of this research was to investigate if and how soil fertility in the smallholder farms of the western and eastern highlands of Kenya is affected by land use and selected household socio economic factors. (2) Changes in soil nitrogen and phosphorus levels over 100 years following conversion of native tropical forest to continuous low input cultivation. In this second part of the study, we used a long-term chronosequence of soil degradation to assess the impact of continuous maize cultivation on the soil N and P fertility and maize productivity of smallholder agricultural systems in the Nandi and Vihiga districts of western Kenya. In addition to quantifying changes in productivity over time, our goal was to (i) understand the long-term dynamics of declining N and P fertility, (ii) assess N fluxes on a chronosequnce of soil fertility degradation following organic fertilizer application and (iii) evaluate the forms and distribution of operationally defined labile and non-labile soil P pools using sequential extraction.

5/10/07 - NO SEMINAR

5/3/07 - Local Impacts of Forest Disturbance, and Country-wide Evapotranspiration Modeling in India (Vishal Mehta, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: This Ph.D. defense seminar will present findings on two research topics that address (1) impacts of forest disturbance on soil and vegetation in a dry tropical forest in India; and (2) GIS-based modeling of monthly reference evapotranspiration for India from 1901 to 2002. (1) Dry tropical forests comprise ~60% of Indian forest cover and have historically been used by local communities for a wide variety of uses, with little information on ecosystem impacts. Results on the impacts of disturbance on soil and vegetation will be presented, based on sampling from 200 sites in Bandipur National Park, southern India (2) The second part of this seminar will focus on modeling of monthly reference evapotranspiration from 1901 to 2002, using public domain global weather datasets as input in GRASS GIS. Model formulation, results and assessment will be presented. The entire dataset is currently publicly available on the India Water Portal (www.indiwaterportal.org) to improve access to hydrologic data for water resource research, planning and management in India.

4/27/07 - Special Seminar The Africa Green Revolution has taken off: Progress so far and emerging challenges (Bashir Jama, Policy Advisor, Agricultural and Rural Development, Bureau for Policy Development, UNDP, New York) Abstract: Africa is also the only region in the world that has not experienced a Green Revolution, which raised agricultural productivity in other parts of the world. Launching an African Green Revolution to increase agricultural productivity – particularly among Africa’s smallholder farmers – is therefore central to ending hunger and extreme poverty. It is against this background that UN Secretary-General in July 2004 called for a uniquely African Green Revolution for the 21st Century to increase productivity in environmentally sound ways. The green revolution needs to tackle five interconnected constraints faced by smallholder farmers: (i) low and declining soil fertility, (ii) poor access to improved seeds and planting materials, (iii) dependence on rain-fed agriculture and poor management of water, (iv) insufficient agricultural extension services, and (v) lack of access to markets. Many countries in Africa have headed the call, and are developing comprehensive strategies and are making significant progress in implementing the green revolution, within the broader context of achieving the Millennium Development Goals by 2015. Many research and development agencies are also providing tremendous support. This seminar will highlight the progress so far and some key challenges emerging. (Note date, time and room changes: 2:00 pm, 101 Bradfield Hall)

4/26/07 - Are Nanoparticles Really "Nano" in the Environment? Monitoring the Aggregation of Titanium Dioxide Nanoparticles in Dilute Electrolytic Solutions (Rebecca French, Master's Candidate, Crop and Soil Sciences, Cornell University) Abstract: Nanotechnology is a booming industry with applications in fields as varied as space exploration and health care. However, the unique properties of nanomaterials that make new technologies possible also imply that current regulations may not be sufficient to protect human and environmental health. Government and nonprofits are calling for basic research to determine the impact of these materials on the environment including their fate and transport in soils. Although studies show that some nanoparticles are able to move through porous media, they also indicate that the particles have a strong tendency to aggregate under environmental conditions. Titanium dioxide nanoparticles (nano-TiO2) are currently used in environmental remediation schemes, sunscreens, and paint products. Such use increases the likelihood that nano-TiO2 will be introduced into the environment, as do accidental spills and disposal associated with its use by industry. Toxicology studies indicate that nano-TiO2 may not be as benign as its bulk counterpart. In this context, this study investigates the aggregation kinetics of nano-TiO2 at ionic strength and pH ranges typical of soil solutions. As shown by dynamic light scattering (DLS), nano-TiO2 exhibits rapid aggregation, going from a primary aggregate size of 50 nm to aggregates of 1-3 micrometers in diameter after only 30 minutes of exposure to 20 mM NaCl at pH 4.5. The rate of aggregation increases as pH nears the particles’ zero point of charge (ca. pH 5.6), and in the presence of CaCl2. DLS measurements also indicate that the aggregates’ size distribution becomes increasingly polydisperse with time. Aggregate sizes will be verified by optical and transmission electron microscopy. The results provide a good starting point for addressing broader questions about the fate of nanoparticles in the environment.

4/19/07 - NO SEMINAR

4/12/07 - Competition for Above and Below Ground Resources Among Annual Species from the Plant to the Field: Quantification, Analysis and Modeling (Andres Berger, PhD Student, Earth and Atmospheric Sciences) Abstract: Competition for resources is common in both mono-species (crop) and multi-species (crop-weed) systems. There is still an important lack of knowledge and understanding of the mechanisms involved in competition for resources and particularly on how these mechanisms may interact. Furthermore, crop-weed competition is a dynamic process that depends on changing weather and soil conditions, as well as on plant community factors, such as density and spatial arrangement. Mechanistic crop-weed simulation models offer a computational approach for dynamically exploring interactions among the diverse drivers of competition. They can also provide a quantitative estimation of the potential competitiveness of weeds which can then be used as a component of precision weed management. In this seminar I will present results from our experiments on below-ground zone of influence, patterns of soil water acquisition by weedy and weed free corn, and soil nitrogen as a driver of growth. I will also present the main features of the model we are developing along with preliminary results and future directions.
AND
Assessing the Effects of Cry3Bb Bt Corn and Insecticides on Decomposer Organisms and Plant Residue Carbon Turnover and Fate in Soil (Kai Xue, Graduate Student, Crop and Soil Sciences, Cornell University) Abstract: Transgenic Bt corn variety MON863 expresses the Cry3Bb protein, which has insecticidal activity against certain species of corn rootworm. MON863 was released for commercial use in the U.S. in 2003. Despite the rapid adoption of Bt crops by farmers, public concern continues to mount over the potential environmental impacts of these crops. In our study, the effects of Cry3Bb Bt corn on carbon allocation, depomosition rate and decomposer organisms were evaluated to provide information for industry and for regulatory agencies to aid them in policy decisions and provide the public with additional information by which to evaluate the potential environmental impact of Bt corn. So far, no negative effect of cry3Bb Bt corn was found in the measurements we tested.

4/9/07 - Special Seminar Advanced 15N-based techniques to trace nitrogen transformations and N2O emissions from stream sediments exposed to high N and OM loads (Professor Avi Shaviv, Soil and Environmental Chemistry, Head, Department of Environmental, Water and Agricultural Engineering, Technion University, Israel) (Note date change)

4/5/07 - NO SEMINAR

3/29/07 - Soil Characterization by VNIR Reflectance Spectroscopy and its use with Spatial Statistics (Ali Bilgili, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: Soils often show high spatial variability within and across fields, which requires the analysis of large sample sets to estimate global or regional means, which may be prohibitively expensive with conventional laboratory techniques. Visible-Near Infrared Diffuse Reflectance Spectroscopy (VNIRS) shows great promise for rapid and inexpensive assessment of soil physicochemical and biological properties both in the laboratory and in situ. VNIRS may also be combined with geostatistical methods to optimize sampling efficiency and spatial estimation. This study investigated the feasibility of VNIRS to predict various soil properties of soil samples collected on a 25x25 m sampling grid over 32 ha (800x400m) in a semiarid area of Turkey. Partial Least Square Regression (PLS) and Multiple Adaptive Regression Splines (MARS) were applied for data analysis, and results were validated with cross validation and independent validation sets. It is concluded that several important soil variables used in environmental modeling can be predicted successfully. The overall success was dependent on the range and autocorrelation between soil variables rather than different statistical method. VNIRS was also compared with (co) kriging analysis for the same unknown sampling points using different sampling designs. In some instances, especially for soil organic matter, VNIRS always gave better prediction results, while for other properties the results of both methods were comparable.
AND
Farming for Beetles: Invertebrate Weed Seed Predation Assessed in (1) A Transition to Organic Cash Grains Study and (2) A Cry3Bb Bt Corn System (Rachel Shuler, MS Candidate, Crop and Soil Sciences, Cornell University) Abstract: Weed seed predation by invertebrates was investigated in two distinct annual cropping systems. Both studies were located less than 250 meters apart on the Robert B. Musgrave Research Farm near Aurora, NY. One study investigated the economically difficult transition period from conventionally managed continuous corn to organic cash grains. Seed predation varied significantly by crop type in the three year corn/soybean/spelt-clover rotation, with the highest predation rates in the spelt-clover. No weed or nutrient management treatments significantly impacted seed predation rates. While weed seed predation could never hope to entirely supplant cultivation or herbicide application as stand-alone weed control, this type of research can make it a more practical component of integrated weed management, particularly in low-input/organic cropping systems. The other study, conducted simultaneously in 2005 and 2006, compared the non-target impacts of Cry3Bb Bt corn to conventional broad spectrum soil insecticides for controlling corn rootworms, Diabrotica spp.(Coleoptera: Chrysomelidae). Invertebrate activity density was significantly lower using the broad spectrum insecticide; however, weed seed removal rates did not vary by insecticide treatment. This study also had a significant methodological component, calibrating the behavioral impact on seed predators of two different weed seed predation setups. Impacts of seed predation method were significant and varied by weed species, leading to important prescriptions to standardize future research in this field. Geospatial analysis also showed significant month-dependant spatial autocorrelation of both seed removal and predator activity density. Invertebrate communities and associated weed seed predation were also significantly different in the Cry3Bb Bt corn and the adjacent transitional cash grains system.

3/22/07 - SPRING BREAK

3/15/07 - Effect of Management Choices in the Old Orchard on Apple Replant Disease Severity (Angelika Rumberger, Research Associate, Crop and Soil Sciences, Cornell University) Abstract: Apple replant disease (ARD) affects young apple trees in replanted orchard sites. The symptoms include stunted growth, necrosis of feeder roots, and reduced yields. A wide variety of biotic (like root-lesion nematodes, Phytophthora spec., Fusarium spec. etc.) and abiotic (like soil compaction, nutrient imbalances, toxic residues) factors contribute to ARD in site specific combinations. The most promising ARD-management strategies include soil fumigation, the use of disease tolerant rootstocks and replant in previous drive lanes rather than in the old tree-rows. So far little is known about how orchard management practices in the previous orchard might affect subsequent replant problems. We conducted two biotests testing for the effect groundcover management systems and choice of rootstock variety in the old orchard on ARD severity. Both, weed management practices and choice of rootstocks in the old orchard can affect ARD.

3/8/07 - Arsenic Contamination in Ground Water and Soils: Spatial Variability and its Effect on Arsenic Uptake, Crop Growth and Grain Yield in Rice (Oryza sativa) (Zia Ahmed, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: In Bangladesh, irrigation water is thought to be a major arsenic pollutant of the soil-plant system, and an additional public health hazard along with high-arsenic drinking water. Geostatistical methods for describing spatial distributions of arsenic in the water-soil-plant system are an integral component for risk assessment of this contaminant. We collected ground water from 161 selected shallow tubewells (STW) used for irrigation of rice. Paddy soil (0-15 cm depth) and rice samples were collected from a 1 m2 area at each STW site. The water, soil and grain samples were analyzed for total arsenic. Variograms analysis showed that arsenic concentrations in water were more spatially dependent than arsenic in soil and rice grain. No clear similarities are visualized among the kriged maps of water, soil and grain arsenic content. However, soil arsenic was higher in the low lying Ganges Tidal Flood Plain AEZ than in the High Ganges River Flood Plain AEZ. To some extent, soil arsenic is influenced by seasonal flooding in both rice and no-rice cultivated soils. Multiple regression analysis showed that arsenic and iron levels in water, soil arsenic, silt content and organic carbon were significant variables influencing the concentration of arsenic in rice grain. Nevertheless, the model explained only 19% of the variability in grain arsenic content. Adding a variety term into the MLR model significantly improved the goodness of fit (R2 = 41%), indicating the influence of variety on arsenic accumulation in grain. To know the effects of genotypes x environment (GXE) on rice grain arsenic content, 20 boro (dry season) and 18 wet season rice varieties were grown in 10 locations in Bangladesh. It was observed that most of the variations of grain arsenic content were explained by the environment. In a geenhouse experiment at Cornell University, it was observed that growth of the 18 dry season varieties from Bangladesh were suppressed in high arsenic soils (53 ppm). All short duration vatieties performed better than long duration varieties in terms of phytotoxicity and grain yield production.

3/1/07 - World Food Prize Reception Dean Susan Henry invites CSS faculty, emeritus faculty, staff, and students to a reception in honor of Dr. Colin McClung, Cornell alumnus (M.S. '49, Ph.D. '50) in soil science and co-recipient of the 2006 World Food Prize for his pioneering work in discovering, assessing and ameliorating soil fertility constraints to agricultural production in the Brazilian Cerrado during the 1950's < http://www.worldfoodprize.org/>. The program will include a short film profiling the three WFP Laureates for 2006, reflections and poster presentations by Dr. McClung, his colleagues, and scientists from North Carolina State University and Cornell University who partnered with fellow Brazilians during the 1970's and 80's to bring this vast area of central Brazil into production. (Note time and room changes: 4:30 - 6:30 pm, G10 Biotechnology Building)

2/22/07 - How Close to Home Might We Grow Our Food? Mapping Potential Foodsheds in New York State (Christian Peters, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: A foodshed is the area from which a population derives its food supply. Although food on American tables has never been more global than it is today, a small, but growing, number of people believe that producing more food locally will help to address the economic, environmental, and social ills of the modern food system. However, little analysis exists to evaluate the merits of such a strategy. In the interest of filling this information vacuum, this talk will describe a spatial analysis which mapped potential local foodsheds for population centers in New York State. A combination of conventional geographic information system tools and optimization modeling were used to estimate the minimum distance within which food needs could be met and the types of foods which are most likely to be produced locally. The findings suggest that a significant share of food could be supplied locally or regionally, though the associated impact on fuel use and greenhouse gas emissions would depend on the efficiency with which goods were transported to market.

2/15/07 - Arsenic and Rice: Consequences of Biogeochemistry and Crop Production Practices (John Duxbury, Professor AND Yamily Zavala, Postdoctoral Associate, Crop and Soil Sciences, Cornell University) Abstract: Biogeochemical processes have led to the accumulation of soluble arsenic in shallow groundwater in the Bengal basin. This water is now used to irrigate rice, which results in flows of arsenic into the environment and the food system. Rice productivity and quality are both adversely affected. In the United States, arsenic in various forms has been widely used as an insecticide and defoliant in cotton. Residual arsenic also adversely affects rice production in the southern USA. A survey of rice available in supermarkets and specialty stores showed large differences in the arsenic content of rice available to consumers in upstate NY.

2/8/07 - The Global Digital Soil Properties Map Project (GlobalSoilMap.net) (David Rossiter, Professor, Senior University Lecturer in the Department of Earth Systems Analysis (DESA), International Institute for Geo-Information Science and Earth Observation (ITC), Enschede, The Netherlands) Abstract: There is a need for accurate, up-to-date and spatially referenced soil information. This need has been expressed by the modeling community, land users, and policy and decision makers. This need coincides with an enormous leap in technologies that allow for accurately collecting and predicting soil properties at fine resolution. This project proposes to make a new digital soil map of the world using state-of-the-art and emerging technologies for soil mapping and predicting soil properties. This dynamic digital map will be supplemented by interpretations and pedotransfer functions for use by modelers and other users of soils data in a range of global issues such as food production, hunger eradication, climate change, regional watershed modeling and environmental degradation. A workshop was held at Lamont-Doherty Earth Observatory (USA) in December 2006, and attended by 30 scientists from universities, research centres and developmental organizations across the globe. The group has formed a consortium that will seek funding for this major global effort. The seminar will present more detail on one key aspect of this effort: rescue and renewal of legacy soils data.

2/1/07 - NO SEMINAR

1/25/07 - In-sourcing Our Food: Scaling Production and Distribution for Local Viability (Joel Salatin, Grass Farmer, Polyface Farm, Swoope, VA) Abstract: From backyard to beyond and from farm gate to foodshed, today's alternative food movement offers a fundamentally different and innovative approach. Marrying techno-glitzy to heritage wisdom, local food entrepreneurs bring marvelous answers to modern problems. Solving problems from bioterrorism to food pathogens, e-dominated transparent farms connected to their foodsheds use less energy and give more satisfaction emotionally, economically, and environmentally. As an equal but opposite reaction to the industrial global out-sourced food action, the local food movement is viable, vital, and viral. We can make it happen today. COSPONSORS: NWAEG, the Department of Crop and Soil Sciences, Cornell Dining, and funded in part by the GPSAFC. (Note time and room changes: 4:00 pm, 233 Plant Science)

FALL 2006

12/14/30/06 - Soil Structure Assessment via Wavelet Analysis of Micropenetrometer Traces (Chun-Yu Wu, PhD Student, Crop and Soil Sciences, Cornell University) Abstract: Soil structure, along with the associated concept of "tilth", has been frequently mentioned in recent years as one of the essential attributes by which to gauge the "quality" or "health" of soils. Much about the concept of soil structure is well understood, but its quantification remains a vexing, challenging problem to this date. Laboratory methods to determine the size distribution and the stability of soil aggregates have been increasingly criticized recently as artifactual, and various authors have argued that what we currently refer to as "soil structure" does not exist in the soil in place, prior to its disruption. There is therefore a need to assess in situ, and to quantify, the degree to which soils exhibit any kind of micro-architecture. At this point only one method, the very ingenious spectral analysis of micropenetrometer traces, offers the potential to provide this quantification in a rapid and reliable manner. There is, however, a number of nagging questions about this technique that would need to be addressed and answered before it can become a routine tool for field use. In this context, the key objective of this proposal is to carry out a detailed study of the analysis of micropenetrometer traces, and to work out a number of unresolved aspects of the technique. Specifically, we intend to confirm that the apparent periodicity manifested by micropenetrometer traces in field soils is not the result of a ratchet-like process that would occur indifferently in aggregated as well as non-aggregated soils, as long as soil moisture falls within a certain range. We also shall determine the extent to which the information on soil micro-architecture or aggregation, obtained via spectral or wavelet analysis of micropenetrometer traces, is sufficiently independent of the moisture content of the soil at the time of measurement (at least in non-swelling soils), and that, therefore, independent soil moisture determinations are not required. In addition, we shall carry out a careful light-, laser scanning-, and scanning electron microscopic analysis of the organo-mineral structures that are associated with the repeating frequencies in the transformed micropenetrometer traces. Finally, we shall evaluate the conditions (e.g., minimum number of points) under which micropenetrometer traces can be analyzed by decomposition with wavelets, and whether this analysis provides significantly richer, localized information than the classical spectral methods. The outcome of this research will be a fully worked-out and reliable method to quantify the micro-architecture of soils in situ, without significant disruption. We expect that this improved method will be invaluable in future studies concerning the quality and health of soils, and the impact of agricultural practices on them.

12/07/30/06 - Influence of Soil Texture and Management Practices on Soil Organic Carbon Stocks in the Indo-Gangetic Plains (Sanjay Gami, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: The rice (Oryza sativa L.) - wheat (Triticum aestivum L.) rotation has emerged as a major production system in the Indo-Gangetic Plains (IGP) of South Asia. However, the productivity of this cropping system is either stagnating or declining. Under this system, wetland rice culture destroys soil aggregates and released organic matter mineralizes readily in the aerobic phase of the rotation leading to severely depleted soil carbon contents. The goal of this study was to assess the influence of soil texture on carbon stocks of IGP soils under native forests and rice-wheat cropping to provide a perspective on the potential for carbon sequestration in agricultural soils. Three long-term soil fertility experiments (LTFEs) were sampled to understand the effects of nutrient and organic inputs on soil organic carbon (SOC) stocks under conventional tillage. Regression analyses showed linear increases, but wide variability, in SOC with increasing silt+clay content at all depths for both forest and cultivated soils. In LTFEs, SOC stocks were highest in the FYM treatment and the no tillage-grassland and lowest in the cultivated control and NPK treatments; residue return and reduced FYM inputs gave intermediate SOC stocks. The SOC stock in the grass control was similar to that in the FYM treatment, suggesting that a change to no tillage would provide a SOC benefit equivalent to adding 4 Mg ha-1 dry wt of FYM/crop. There was little or no impact of NPK fertilization on SOC stocks with crop residue removal. Trends in animal populations and FYM availability in the study areas and throughout the Indo-Gangetic Plains make it impractical to consider using FYM to increase SOC stocks. Shifting to no-tillage agriculture presents the best option for increasing SOC stocks. The RothC-26.3 model was used to predict SOC levels and dynamics. Methods for using 13C labeling techniques for both rice and wheat crops will be described.

11/30/06 - From Past Iron Making to Modern Environmental Research: Effects of Temperature and Time on Chemical Properties and Surface Charge of Charcoal (Chih-Hsin Cheng, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: In recent years, charcoal has received increasing attention owing to its potential importance in a wide range of biological and chemical processes. Charcoal samples from historic charcoal blast furnaces were conducted in this research. The objective was to study the effects of temperature and time on chemical properties and surface charge of charcoal. Our results showed that charcoal could be gradually oxidized, even under room temperature. The historic charcoal samples further demonstrated this long-term natural oxidation. With the formation of oxygen-containing functional groups, surface charge of charcoal would be modified, in which the positive surface charge would decrease and the negative surface charge would increase. The point of zero net charge (PZNC) dropped from pH 7 in the fresh charcoal to pH below 3 in the historic charcoal. Our data also showed that higher mean annual temperature (MAT) and higher soil pH could lead more negative charge of charcoal. The results would be extended to reinforce and clarify some misunderstanding points in the past, such as the deterioration of charcoal during storage or the reason to continue using charcoal instead of anthracite for furnace fuel in the 19th century.

11/23/06 - NO SEMINAR

11/16/06 - NO SEMINAR

11/09/06 - Soil Organic Matter Degradation and Associated Threshold Dynamics in Kenya - From Landscape Biogeochemistry to Nanoscale Biogeocomplexity (James Kinyangi, PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: Forest and agricultural conversions are a major source of land use potential for smallholder agriculture in the tropics. The productive capacity of these landholdings is now diminished due to excessive nutrient mining from long-term cultivation and organic matter degradation without replenishment of mineral nutrients. As part of the NSF biocomplexity project, we have assessed the biogeochemistry of soil degradation and associated threshold dynamics of 100+ years on three chronosequence sites in 800 km-2 settlement corridor proximal to Kakamega-Nandi forest margins. Results from C, N, d ¹³C, d ¹⁵N and extractable cation charge (+) show that; degradation dynamics constitute forest and agriculture equilibrium states, where distinct threshold responses emanate from organic matter decay and loss in the cation charge from the exchange complex. Infrared spectroscopic investigations reveal that the microscale variability in the location of organic matter is unaffected by changing land-use but the nanoscale biogeocomplexity studied by C NEXAFS, show evidence of alterations in organic matter functional characteristics, which however, do not manifest at the landscape level. From these chronosequence data, we demonstrate how multiple scale responses can lead to a near permanent loss in the ecological function of tropical soils to support agriculture.

11/02/06 - The Significance of Free-living Noncultivated Diazotrophs in Soil (Florence Hsu, Graduate Student, Crop and Soil Sciences, Cornell University) Abstract: Most knowledge of biological N-fixation in soils is based on cultivated strains and symbiotic systems. In the soil, nonculivated free-living diazotrophs may also play an important role for N fixation. Model systems for N-fixation in soil are generally based on a narrow range of cultivated diazotrophs which utilize simple sugars or organic acids as their primary sources of C and energy. However, these energy resources are often limited in soils especially below the soil surface. Therefore, free-living noncultivated diazotrophs have often been neglected historically due to difficulties associated with cultivating these organisms. Recent evidence suggests that a wide diversity of free-living noncultivated nitrogen fixing organisms exist in soil. These noncultivated N-fixers remain poorly characterized, and their contributions in soil have yet to be determined. In this project, molecular techniques that can avoid the limitations of traditional cultivation of microorganisms will be used to investigate these noncultavated diazotrophs in soil and to assess their contribution to soil N fixation.
AND
Hyperspectral Sensing of Soil Pedons for Soil Classification and Survey (EJ Neafsey, Graduate Student, Crop and Soil Sciences, Cornell University) Abstract: Diffuse-reflectance near-infrared spectroscopy has demonstrated substantial potential in the rapid, accurate estimation of key soil properties. Many of these soil properties are diagnostic for the purpose of soil classification and survey. As many of the United States' soil surveys approach 40-50 y in age, there is an interest in using proven remote sensing platforms to supplement the current methodologies employed in the soil survey update process. This study is guided by the following objectives: (1) characterize the hyperspectral response of selected soil chemical and physical properties that are important to soil survey, (2) assess quality of hyperspectral data collected in situ as an aid to field-based soil survey operations and (3) compare the quality and usefulness of hyperspectral data collected using laboratory- and field-based methods for soil classification and survey. The hyperspectral responses of selected soil samples from pedons in Allegany and Ontario Counties in western New York were correlated with Cornell Nutrient Analysis Laboratory (CNAL) and National Soil Survey Center (NSSC) soil properties values using Partial Least Squares 1 (PLS1) regression. In addition, the degree of spectral discrimination among soil samples from known horizons was examined using principal components analysis (PCA). Also, an unaligned 1.2 m ?0.2 m grid with a resolution of 0.05 m (n = 124 sample points) was created on one pedon in Allegany County to assess the feasibility of predicting the spatial distribution of selected soil properties throughout a portion of the soil profile.

10/26/06 - Legume Crop-based Soil Phosphorus Management and Effects on Maize (Zea mays) Productivity in Western Kenya (Jane Kapkiyai, PhD Candidate, Crop and Soil Sciences, Cornell University). Abstract: The low availability of phosphorus (P) in many tropical agricultural lands is a major constraint to crop production. Some legume genotypes posses stress response mechanisms that enhance their P accessibility in low P soils and may be useful components for integrated soil fertility management in these soils. In this study, some selected legumes were assessed for their performance in soils of contrasting levels of soil fertility degradation arising from different management histories, P dynamics and adsorption following incorporation of the legume residues were measured, and the effect of the legumes on growth and nutrient uptake of maize (Zea mays) determined. Three non- P responder species, pigeon pea (Cajanus cajan), white lupine (Lupinus albus) and groundnut (Arachis hypogaea) and two P responders, soybean (Glycine max) and Lablab (Lablab purpureus) were used in the study. There was no site effect on plant dry matter production and P uptake in the field, but in pots, the P responders showed higher performance in high fertility soil. Greater anion exchange membrane (AEM) P values were obtained in the less degraded soil, and varied across sampling times. The plant residues depressed AEM P in the highly degraded soil but increased it in the less degraded soil. Whether alone or mixed with residue, Minjngu rock phosphate (MRP) caused a gradual increase in AEM P. The most degraded soil adsorbed more than twice the amount of P adsorbed by the non-degraded soil. Maize and soybean crop residues reduced P adsorption while white lupin had no effect. Maize produced more biomass and higher grain yields and had a higher nutrient uptake when grown in association with or after legumes than sole or after maize. These results show a promising potential of the studied legumes to contribute to P management in the nutrient depleted cropping systems of western Kenya. It was apparent that the benefit of the legume crops on soil nutrient availability and maize growth depended on the initial soil status.

10/19/06 - Can Native Tallgrass Prairies Serve as a Model for Sustainable Agroecosystems? (Steve Culman, Graduate Student, Crop and Soil Sciences, Cornell University) Abstract: A model agroecosystem would support long-term nutrient export mostly though endogenous sources - namely biological nitrogen-fixation and mineral weathering of soil. The native tallgrass prairies of north-central Kansas may meet these requirements, as they have been annually hayed for the last 75 years or more without experiencing a decline in above ground biomass yield. This long-term nutrient removal with no anthropogenic nutrient inputs can be contrasted to neighboring annual agricultural fields which require a large amount of nutrient inputs to sustain current yields. Research at the Land Institute, in Salina, Kansas has catalyzed a collaborative effort to look at differences in soil biology and nutrient dynamics between prairies and annual agricultural fields in order to better understand the mechanisms which allow prairies to export large amounts of nitrogen over time. My specific role in this effort is to explore the differences in soil bacterial diversity and nitrogen-fixing bacterial gene diversity between annual cropping systems and native tallgrass prairies.
AND
Long-term Removal of Maize Residue for Biofuel: Will It Affect Soil Quality? (Bianca Moebius, PhD Student, Crop and Soil Sciences, Cornell University) Abstract: Recent increases in fuel prices are inspiring discussion about potential methods for renewable energy production from crop-based biofuels. The use of residues for biofuel production would prevent diversion of products/feedstock from the food and feed supply. However, the potential economic benefits of crop residue removal must be weighed against the potential impacts on soil quality. This study, located in Chazy, NY, evaluated the long-term effects of 32 years of maize residue harvest on soil quality under plow till and no till systems on a Raynham silt loam, on physical, chemical, and biological soil quality indicators. Effects of residue management were compared to those of tillage, and a strategy for sustainable maize residue harvest for biofuel production was identified. Twenty-five indicators were used in the assessment, including standard chemical soil test measurements, aggregate stability, bulk density, penetration resistance, saturated hydraulic conductivity, several porosity indicators, total organic matter, parasitic and free living nematode counts, root rot and decomposition ratings, potentially mineralizable nitrogen and glomalin (autoclave-stable soil protein). Only 8 of the indicators measured (Bulk density, AWC, K, Mg, OM, Decomp, EEG and TG) were adversely affected by residue harvest. Of these 8 properties affected by residue treatment, all except K, Mg and EEG were equally or more significantly affected by tillage, and only K was not significantly affected by tillage. Tillage treatment as a main factor significantly affected 15 out of the 25 measured indicators. In addition to those affected by both main factors (tillage and residue), WSA, N, Al, Mn, Zn, pH, Parasitic Nematode Populations, and PMN were only affected by tillage. This study suggests that, on a silt loam in a temperate climate, long-term residue removal has limited adverse effects on soil quality. Residue removal appears sustainable when combined with no till management.

10/12/06 - Assessing the Effects of Bt Corn and Insecticide on Arbuscular Mycorrhizal Fungi and Plant Residue Decomposition in the Field (Luz Marina Londono, MS Candidate, Crop and Soil Sciences, Cornell University) Abstract: The use of genetically-modified crops such as transgenic Bt corn is rapidly increasing worldwide.ÿ Studying their potential impact on microbial ecosystems is critical for determining their safety and for establishing appropriate regulatory policies. While some environmental impact assessment studies have been conducted, these have been largely carried out in the laboratory setting.ÿ Field studies are therefore needed.ÿÿ Here, we evaluate: 1. The effect of Cry3Bb transgenic Bt corn and insecticide on abundance, activity and diversity of AMF; and 2. Differences between microbial communities that colonize residues of Cry1Ab Bt corn from those that colonize residues of non-transgenic isolines.ÿ Our findings suggest that transgenic Bt corn has no effect on the soil microbial communities studied.

10/05/06 - Size Matters: Buckingham Numbers in Biological Systems (Clay Mitchell, MS/PhD Candidate, Crop and Soil Sciences, Cornell University) Abstract: Dimensional analysis applications to biological systems involve far more useful tools than just allometry.ÿ In applying Buckingham pi theorem to problems as diverse as bacteria movement, fruit bruising, and carbon fluxes above forest canopies, we will explore how to design more efficient and robust experiments and gain more knowledge from the observations that we have.ÿ We will cover the mathematical basis for the theorem and incorporate recent generalizations.ÿ The goal is to cover the theorem sufficiently for you to apply it to your own work immediately. (Note room change: 1102 Bradfield Hall)

9/28/06 - Plant Communities of the Central Finger Lakes Region (Chuck Mohler, Senior Research Associate, Department of Crop and Soil Sciences, Cornell University) Abstract: The Central Finger Lakes region of New York contains a wide diversity of natural forest and open wetland plant communities and communities developing on abandoned farm land.ÿ The seminar will discuss methods used for sampling and classifying the vegetation of the region and then present an overview of community types in relation to environmental and historical factors that control the composition of vegetation. The talk is intended to introduce a new book, "Guide to the Plant Communities of the Central Finger Lakes Region", by Charles L. Mohler, Peter L. Marks and Sana Gardescu.

9/21/06 - Black C Effects on the Biogeochemical Cycling of Soil Nutrients and Organic C in Amazonian Dark Earths (Terra Preta De Indo) (Biqing Liang, Graduate Student, Department of Crop and Soil Sciences, Cornell University) Abstract:ÿBlack carbon (BC) was found to increase soil cation exchange capacity and to be a key contributor to the high fertility in Amazonian Dark Earth soils, which are unique compared to other commonly found and poor adjacent soils in the humid tropics. Here we study the mechanisms in which BC is involved in soil nutrient retention and organic C cycling. Novel techniques such as synchrotron-based NEXAFS (Near Edge X-ray Adsorption Fine Structure Spectroscopy), NMR (Nuclear Magnetic Resonance Spectroscopy), Microprobe, coupled with density fractionation after long-term incubation with stable isotope labeled material have been used to study the surface chemical properties of BC (especially C functionality), bulk C quality (aromaticity), C, O and cation elemental distribution within soil aggregates, C distribution and long-term dynamics within aggregates. Our research questions are: i) How stable is BC? ii) How does BC surface properties affect soil organic C and nutrient cycling? and iii) How to discriminate the portion of reactive C functional groups by BC oxidation from contribution from adsorption of non-BC materials? It was found that interior regions of BC particles remain highly aromatic even after 7,000 years of exposure in soils. BC can be oxidized on the surface and absorption of labile organic soil C can occur. Both oxidation and absorption of BC lead to creation of reactive C functional groups and further soil nutrient retention in the soils. Studies of depth profiles allowed us to distinguish between the contribution of either oxidation or absorption. The understanding of the basic chemistry of BC and its effects on soil nutrient retention and organic C cycling provides an important knowledge base for sustainable soil fertility management and improving soil fertility with bio-char applications.

9/14/06 - NO SEMINAR

9/7/06 - Modeling Nitrogen Fluxes in Maize Production: Application to the Humid Northeast US (Jeff Melkonian, Senior Extension Associate, Crop and Soil Sciences, Cornell University). Abstract: Results from a number of experiments have shown that seasonal weather variability strongly affects soil nitrogen (N) processes, maize N uptake and N losses to the environment. We have developed a composite dynamic simulation model to estimate soil N dynamics and maize N uptake in response to different soil, climate and management scenarios with the goal of reducing N losses associated with maize production in New York State. The model consists of components of rigorously tested maize/N (Sinclair and Muchow, 1995) and soil N/water (LEACHN; Hutson, 2005) dynamic simulation models. The specific objectives of this work are to provide general, state-wide sidedress N rate recommendations for maize production that account for early season changes in soil N and maize N uptake, develop a web interface that individual users can access to obtain field-specific sidedress N recommendations, and develop a new N leaching index for New York State. More general applications include contributing to the assessment and remediation of N loading in the Upper Susquehanna River Basin as part of the Agricultural Ecology Program at Cornell. I will briefly describe the major crop and soil processes represented in the models, initial testing of the model against field data and recent application of the model for suggested adjustments to the standard sidedress N recommendations for maize in New York State. The web interface for the model, currently under development, will also be presented.

Other Related Seminars
Biogeochemistry and Environmental Change
Natural Resources
Plant Breeding

Fall 2005 and Spring 2006 Seminars
Fall 2004 and Spring 2005 Seminars
Fall 2003 and Spring 2004 Seminars
Fall 2002 and Spring 2003 Seminars
Spring 2002 Seminars
Fall 2001 Seminars
Spring 2001 Seminars
Fall 2000 Seminars
Spring 2000 Seminars