Recent increases in atmospheric carbon dioxide caused by the combustion of fossil fuels and tropical deforestation may result in global warming. Carbon accumulation by regrowing temperate forests, in regions such as the southeastern United States, may have been extensive enough to counterbalance releases of carbon from the tropics. In the Virginia Piedmont, large amounts of carbon have accumulated in phytomass and detritus of loblolly pine (Pinus taeda) plantations and natural forests regrowing on post-agricultural fields. After 50 years, carbon in phytomass of old field plantations was 200,000 kg/ha, twice the amount accumulated by natural forests. Detrital carbon accumulations totaled over 100,000 kg/ha, but were dependent upon amounts of erosional loss prior to reforestation. The forested land area in the southeastern United States has stabilized, and forest conversion is now the primary form of reforestation. Therefore, the region's ability to continue to store carbon has been questioned. Still, the phytomass of late-rotation converted plantations stored 200,000 kg carbon/ha, twice the amount of the natural forests they replaced. In addition, while the harvest of natural forests resulted in small reductions in detrital carbon, it was rapidly restored to over 100,000 kg/ha within 30 years. Houghton et al. (1983) developed a series of models describing carbon dynamics during reforestation. My data show that patterns of carbon accumulation exhibited by regrowing loblolly pine plantations are different from their models. Therefore, modifications of the models are suggested to improve estimates of carbon storage in temperate forests. / Master of Science

"September 2001" / Bibliography: leaves 144-159. / xix, 159 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The two main aims of this study were: 1) to determine if the presence of Calcium carbonate in soil was the reason behind soils from Yorke Peninsula having relatively high OC (organic carbon) contents, given local farming practices, and 2) to determine the effect that the composition of the soils' OC has on the mineralisation rates. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002

In an attempt to investigate the cause of change in the competitive ability between monocots and dicots in a pastureland in Farnham, Quebec under CO2 enrichment, I chose to study the response of Plantago major (dicot) and Poa pratensis (monocot) grown in ambient and elevated CO2 chambers, hypothesizing that a large increase in root biomass of dicots would be observed under elevated CO 2. A transient stimulation of root biomass of Plantago major was found during the first month of CO2 exposure but disappeared later. / The second objective of this study was to examine the effect of 5 years of CO2 enrichment both on root biomass and on total C and N content of roots and soil in the pasture. The largest belowground growth was recorded for Taraxacum officinale. Plantago major responded by achieving the highest aboveground growth. / N content of CO2 enriched roots was reduced. This change in the elemental composition of root tissues might negatively affect the process of decomposition and therefore, the nutrient availability to soil microbes and plants. The observed reduction of NO3 in CO2 enriched soil maybe due to greater N immobilization caused by the expected increase in microbial populations.

Research on soil organic carbon (SOC) within the northern Great Plains has not been clearly documented. Objectives of this study were (i) to inventory literature reporting SOC responses to agroecosystem management, (ii) extract data for the Northern Great Plains Rapid Carbon Assessment, and (iii) summarize data to identify relationships between SOC and land use management. Soil organic carbon at 0 ? 15 cm depth was 1.57 ? 6.87 kg C m-2, 1.56 ? 5.34 kg C m-2, and 1.48 ? 5.48 kg C m-2 under grasslands, conservation tillage (CST), and conventional tillage (CT), respectively. Soils with a Productivity Index (PI) of 80 ? 100 had greater mean SOC (4.14 kg C m-2) across all managements. Correlation between SOC and PI for CT was significant (r=0.240) (P=0.05) and highly significant (r=0.418) (P=0.01) for CST. Management practices for cropland soils combined with productivity potential appear to relate to the C accrual potential of northern Great Plains soils.

No description available.

Successful renovation of wastewater and sludge via land application depends upon sludge-induced soil changes associated with carbon (C) and nitrogen (N) cycles within the soil/plant system. The C, N, and hydrologic cycles within a soil/sludge system receiving a year-round, daily application of paper mill sludge were studied. Soil samples were collected from three locations on a land application site in the Piedmont of Virginia that had received papermill sludge applications for six, two, and no prior years. The average application rate was 4.4 cm/wk, each week of the year, with a N loading of 700 kg N ha⁻¹yr-⁻¹. The column study showed that C and N were still accumulating on the land application site after 6 years, but at a decreasing rate. Based on this study, C accumulation will level out after 13 years of application, but N will continue to accumulate for almost 30 years. As application period increased, soil bulk density increased in the O, A, and B horizons, the percentage of non-capillary porosity fell below 10% in the A horizon and approached zero in the B horizon, and there was a dramatic decrease in the soil's hydraulic conductivity in both the A and B horizons. Nitrogen leaching is expected to increase with time due to high amounts of N in the papermill sludge, a continued narrowing of the C:N ratio, a high percentage of nitrification, and low denitrification rates. Experimental timing and rates of sludge additions were imposed to alter the aerobic/anaerobic properties of the soil system to determine the conditions under which optimum C and N mineralization, nitrification, and denitrification would occur. Application rates were factorially arranged for single or multiple doses on a daily or alternating schedule. The C decomposition and N mineralization processes were both optimized with an increase in the length of cycle; they were maximized with an alternating 9 days on/9 off application schedule. The nitrification potential also increased with the length of cycling, with an average nitrification rate of 96%. Denitrification was minimal in all treatments, with an average denitrification rate of 16%. This was primarily attributed to movement of nitrate-N below the most biologically active zone in the soil column. Sludge renovation will ultimately depend upon the excess N being sequestered in plant biomass or denitrified. Proper management of these processes will ensure that wastes decompose, and that N is stored or evolved as a benign gas rather than leached at unacceptable levels. / Master of Science

Thesis (MPhil (Sustainable Development, Planning and Management))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Sustainable agricultural management practices have a profound impact on soil carbon sequestration. The amount of carbon that can be stored in a given soil is influenced by climate, soil type, and the quality and quantity of organic inputs. Together, the interactive effect of these factors determines the Soil Organic Content (SOC). Sustainable agricultural management practices influencing Soil Organic Matter (SOM) include application of organic amendments, conservation tillage, and use of cover crops, crop rotations, crop residue management, and nutrient management. Increasing SOC enhances soil quality, reduces soil erosion, and increases agricultural productivity with considerable on-farm and off-farm benefits. To assess how management practices affect SOC, two case studies were conducted in Yavatmal district of Maharashtra in India and Lynedoch near Stellenbosch. The first case study examined the differences in SOC content on four farms each managed with 13 different sustainable agricultural techniques and one farm managed under conventional management practices. The second case study investigated the SOC differences between an organic and a conventional vegetable farm. The results of both studies show that farms that are managed under sustainable agricultural practices generally contain higher SOC content than farms that are managed under conventional agricultural practices. / AFRIKAANSE OPSOMMING: Om te bepaal hoe bestuurspraktyke Grondlikke Organise Koolstoff raak, is twee gevallestudies in die distrikte Yavatmal in Maharashtra, Indië, en Lynedoch buite Stellenbosch uitgevoer. Die eerste gevallestudie het die verskille in Grondlikke Organise Koolstoff -inhoud bekyk op vier plase waar 13 verskillende Volhoubare landboubestuurspraktyke het ‟n diepgaande impak op grondkoolstof-beslaglegging. Die hoeveelheid koolstof wat binne gegewe grond gestoor kan word, word deur klimaat, grondsoort en die gehalte en hoeveelheid organiese toevoer beïnvloed. Saam bepaal die interaktiewe effek van vermelde faktore die Grondlikke Organise Koolstoff -inhoud. Volhoubare landboubestuurspraktyke wat Grondlikke Organise Materiaal beïnvloed, sluit in die toediening van organiese verbeterings, bewaringsgrondbewerking, die gebruik van dekkingsoeste, oesrotasies, die hantering van oesresidu en voedingstofbestuur. Vermeerdering van Grondlikke Organise Koolstoff verhoog grondgehalte, verminder gronderosie en vermeerder landbouproduktiwiteit met aansienlike voordele op en verwyderd van die plaas. volhoubare landboutegnieke in die bestuurproses toegepas word, en een plaas wat volgens konvensionele bestuurspraktyke bedryf word. Met die tweede gevallestudie is ondersoek gedoen na die Grondlikke Organise Koolstoff -verskille tussen ‟n organiese en ‟n konvensionele groenteplaas. Die uitslae van albei studies dui daarop dat plase wat volgens volhoubare landboupraktyke bestuur word oor die algemeen hoër Grondlikke Organise Koolstoff-inhoud aantoon in vergelyking met plase wat volgens konvensionele landboupraktyke bedryf word.

In an interdisciplinary study requiring the synergistic association of historical evidence and chemical and biochemical analyses, this thesis investigates the properties and characteristics of historically modified soils known as anthrosols. These soils, developed through the anthropogenic addition of high volumes of organic-rich municipal waste materials to land, including human and animal waste, as part of the waste management practices in medieval urban communities in Scotland at St Andrews, Roxburgh and Elgin, offer an insight to the state and dynamics of these organic material. Soil is one of the most sensitive environmental domains to transformation. These transformations are visible from the alterations to the physical and chemical properties of soil. Anthropogenic activities may leave behind signatures in the soil in the form of artefacts, ecofacts, elemental enrichment or depletion, enhancement in soil magnetic properties and organic matter content. In the historical dimension of this study, the observable features and measurable properties of soil profiles are exploited to reveal past organisation and functions of cultural landscapes by carefully studying the stratigraphic units of soil profile, and examining the association of each unit with settlement artefacts and soil properties. Through comparison with historical records of past events on the respective study sites, the relationship between the soils record of past human activities is observed through physical, chemical and biochemical properties. The historical record is used to assess if such evidence can be used reliably to develop the account of site use for the medieval burghs of Scotland. In the environmental aspect, investigation focuses on the physical and chemical conditions of these soils in terms of their carbon content, composition, residence time estimates and their role in global C cycle and terrestrial carbon budgeting. Past investigations of anthopogenically-deepened soils have been interpreted with respect to historical site use, however, the environmental implications of the resultant accumulated organic material or residue have not previously been considered in much detail. A particular novelty of this aspect of the project is that it is an in-depth examination of anthropogenic soils with known histories extending into the medieval period. This time-depth allows a new understanding of the processes and products of decomposition of known organic materials that were added to soil. The biophysicochemical data obtained from these soils such as their extant organic carbon content and variability with depth, the composition of the various carbon species that together constitute soil organic matter, and biological community and activity (microorganisms and enzymes) provides critical information on the relative recalcitrance, state of decomposition, and the mechanism of stabilisation of these materials in the soil.

A two year study was initiated in 1999 at the Macdonald Campus Farm, on a 2.4 ha site consisting mainly of St-Amable sand to shallow loamy sand (Typic Endoaquent; Humic Gleysol). The site was planted to alfalfa ( Medicago sativa) prior to the establishment of the experimental design and has been planted to corn (Zea mays L.) since 1991. The experiment was set up as a randomized complete block design and consisted of three tillage levels (NT, no-till; RT, reduced tillage; and CT, conventional tillage) and two residue levels (-R, no residues; +R, with residues). This study was performed in order to ascertain the effect of these management systems on soil organic carbon (SOC), particulate organic matter carbon (POM-C), microbial biomass carbon (MBC) levels and soil physical properties. Soil physical properties measured included bulk density, saturated hydraulic conductivity (Ksat), dry and wet aggregate stability, total porosity, macroporosity at -1 kPa and -6 kPa of matric potential, and moisture content. Crop yield was also measured. Results indicated that lower rates of mineralization of POM-C under NT+R in the surface 0--10 cm led to significantly higher SOC at the same depth. There were no significant differences between treatments at the 10--20 cm depth. The MBC was not a good indicator of the differences in soil organic matter levels between treatments. No-till treatments had higher bulk densities, reduced total porosity and macroporosity, increased moisture content, and increased constant-head measured Ksat. Differences in Ksat as measured with the Guelph permeameter, were not significant between treatments, most likely due to increased earthworm activity in NT. There were no significant differences in crop yield in 1999, but a significantly wetter year in 2000 caused lower grain yields in NT+R compared to NT-R and CT+R.

CH$ sb4$ and CO$ sb2$ fluxes were measured in upland boreal forest soils, over the period May 16$ sp{ rm th}$ through Sept. 16$ sp{ rm th}$, 1994, among a variety of vegetation and drainage characteristics. Most upland soils consumed CH$ sb4$, (0.6 to $-$2.6 mg CH$ sb4$ m$ sp{-2}$ d$ sp{-1}$), and produced CO$ sb2$, (0.2 to 26.8 g CO$ sb2$ m$ sp{-2}$ d$ sp{-1}$). CH$ sb4$ consumption showed no seasonal trend, however CO$ sb2$ flux displayed an increasing rate until late August, after which flux rates began to decrease. Differences among the sites examined showed soil temperature and organic matter content to be the primary controls in predicting seasonal mean CH$ sb4$ flux rates. Similarly for CO$ sb2$ flux, soil temperature and C content proved to be the best predictors of seasonal mean differences among the range of sites examined. / Sites could be divided into 2 categories, strong CH$ sb4$ consuming and CO$ sb2$ producing sites, Gillam Aspen, Gillam Pine, OBS Aspen, Burn Moss, Palsa Birch, and YJP Dry and weak CH$ sb4$ consuming and CO$ sb2$ producing sites, Gillam Spruce, OBS Spruce, YJP Wet, Burn Spruce and Palsa Moss. The strong flux sites all exhibited similar trends in soil characteristics as they were the warmest, driest sites with faster nutrient cycling processes and thin ($ sim$2 to 10 cm) organic layers. The weak flux sites were colder, wetter, with slower nutrient cycling, and a thick organic/peat layer ($ sim$20 to 50 cm). The primary visual distinction between these two groups was the presence of a Sphagnum sp. ground cover, which was characteristic of weak CH$ sb4$ consuming and CO$ sb2$ producing sites.