Soluble organic matter represent less than 1% of total soil organic matter (SOM) - but it contributes to many terrestrial ecosystem processes, due to its high mobility and reactivity in soil. Although it has been suggested that soluble organic matter (OM) may serve as an early indicator of soil quality changes as a result of shifts in land-use and management practices, only a few studies have addressed the dynamics of soluble OM in relation to land-use and specifically soil depth. This study focuses on two aspects of soluble OM. In the first part, I hypothesized that extractable OM obtained by aqueous solutions is a continuum of substances that depending on the extraction method can be separated into two operationally different fractions. The size and properties of these fractions may consistently differ among different land uses and at different soil depths. The objective of this part of the study was then to assess dynamics (size and properties, biodegradability and seasonality) of water extractable organic matter (WEOM) and salt extractable organic matter (SEOM) in a sequence of human dominated land-uses at topsoil and subsoil. At the second part of the study, I tested the regulatory gate hypothesis –abiotic solubilization of OM- as a primary controlling factor in soluble OM production. The objective of this study was to evaluate the impact of the microbial activity on the net production of dissolved organic matter (DOM) from the native SOM in the presence of added DOM and plant residue. For the first part of the experiment, the soil samples were collected from four land-uses under bog pine (Halocarpus bidwillii) woodland, tussock grassland (Festuca novae-zelandiae and Heiracium pilosella), cropland (Medicago sativa) and plantation forest (Pinus nigra). The selected land uses were located in the Mackenzie Basin, Canterbury, New Zealand and occurring on the same soils, topography and experienced similar climates. Soil samples were obtained from topsoil (0-20 cm) and subsoil (60-80 cm) at the end of each season (November, February, May and August) during 2007-2008. The sampled soils were adjusted to the same water status prior to extraction. While WEOM was obtained during a mild extraction procedure and using 0.01M CaCl2, SEOM was extracted with 0.5M K2SO4 at high temperature (75οC for 90 min). Both extracts were filtered through a 0.45 μm filter size. In the first part of the study, I assessed the biodegradation dynamics of WEOM and SEOM (spring samples), using a double-exponential decay model. The WEOM and SEOM were inoculated and incubated at 22°C for 90d under aerobic conditions. Subsamples were removed on days 1, 3, 7, 12, 16, 30, 42, 60, 75, and 90, filtered (0.22 μm), and analyzed for organic C and N content, UV absorption, and 13C natural abundance (δ13C). The results of the biodegradation experiment indicated a similar pattern for both C and N of SEOM and WEOM as that of previously shown for soil DOM. However, C and N mineralization rate were considerably larger in the WEOM than SEOM. The parameters of the double-exponential model suggested that regardless of the land-use and soil depth, both the WEOM and SEOM can be modeled in two biological pools, with a largely similar “fast decomposable” but different “slowly decomposable” pools. However, since the extraction was not sequentially followed, a very small portion of the SEOM was comprised of the WEOM and given the greater observed biodegradability of the WEOM, the overall biodegradable portion of the SEOM would be lower than the observed. Despite a greater biodegradability of the organic N than C of both WEOM and SEOM; mainly due to a longer HL of the slowly biodegradable pool of C; the C/N ratio of the samples did not change very much during the biodegradation. This led us to conclude that the biodegradation of soluble OM may occur as a function of N availability. Parallel to C and N loss, a considerable increase in SUVA254 of SEOM, and particularly WEOM occurred during the incubation period. The greater increase in the proportion of aromatic compounds (assessed by SUVA) in the WEOM than SEOM, implied consumption of simple compounds (vs. very humified) during decomposition and further supported the observed faster biodegradation rate of the WEOM. The data indicated a relatively strong correlation (R2=0.66 and 0.74 for the WEOM and SEOM, respectively) between the amount of biodegraded C and the increase in SUVA254. This suggested that SUVA254 can be used as a simple, low-cost but reliable approach for describing the biodegradability of soluble OM, as previously suggested by others. At the end of the bioassay, the 13C natural abundance of the WEOM was significantly depleted, and showed a clear relationship with the proportion of the biodegraded C. This confirmed the previously suggested preferential biodegradation of simple organic constituents (13C enriched), resulting in the accumulation of more depleted 13C compounds (often recalcitrant compounds). Moreover, the results of the δ13C technique revealed that the relatively greater 13C enrichment of the WEOM obtained from subsoil, seems to be due to the presence of root exudates (often highly 13C enriched). In contrast, a proportionally greater 13C depletion observed in the SEOM particularly at subsoil samples, suggests that there is a close relationship between the SEOM and the typically 13C depleted humified SOM. The results of the biodegradation model (half-life of both C and N), in addition to dynamics of SUVA254 and δ13C of the WEOM and SEOM were very comparable between top and subsoil samples. This implied that the potential biodegradability of soluble OM under laboratory conditions does not necessary reflect the reported lower in situ biodegradability at soil depth, in agreement with recent evidence suggested by others. Instead, this may be largely due to the lack of optimum conditions (oxygen, nutrients, and moisture) for the decomposer community at soil depth. Although there was a tendency for a generally greater biodegradability of the samples from the soils under the crop land (both WEOC and SEOC), along with relatively greater increase in SUVA, there was not a consistent trend of the effect of land use on the biodegradation of either WEOM or SEOM. The lower C/N ratio of the soils under the crop land seemed to be related with the observed proportionally greater biodegradability of these soils. During the second part of the study, I assessed seasonal variations of the size and properties of the previously defined WEOM and SEOM, collected from top-and subsoil from the land-uses. I observed that 10-year after conversion of the degraded tussock grassland to cropland or plantation, the total C stock of topsoil (0-20 cm) when above- and below-ground plant biomass is excluded; has remained unchanged. This was attributed to the limited biomass production of the region, more likely as a result of low productivity of the soil, but also harsh climatic conditions. Not only soil depth, but land-use affected both C concentration and C/N ratio of soil organic matter (SOM), with the greatest C concentration of soils under grassland and plantation in topsoil and subsoil, respectively. Despite the WEOM, the size of SEOM was largely unaffected by land-use and soil depth; instead, the properties of SEOM was more consistent with the effect of soil depth. Given the observed large temporal and spatial variability of the WEOM, the study suggests that the SEOM more consistently reflects the influence of land use and soil depth. No consistent effect of seasonality was observed in terms of size or properties of the SOM and the WEOM and SEOM. Overall comparison of the size and properties of the WEOM and SEOM indicated that OM extraction efficiency may vary largely, depending on extraction conditions. Using more concentrated salt solutions consistently yielded greater amount of OM (N, and especially C) release from soil with properties resembling more those of total soil OM (more humified) compared to the WEOM. The SEOM was also less variable by time and space. The last part of the study was aimed to assess biotic vs. non-biotic solubilization of OM in the presence of added plant residue. Given the need to recognize the source of the solubilized OM during the experiment, I used enriched (13C) plant residue as the source of fresh OM. The above-ground part of ryegrass was added to soil either as plant residue or residue extract (extracted with CaCl2 followed by 0.45μm filtration) -termed DOM. These two forms of added OM (residue/DOM) were conceived to represent two levels of bioavailability for the decomposer community for further assessing possible biotic solubilization of OM. Two soils similar in their OM content and other properties, but different in mineralogy were selected for the experiment. Soils were incubated for 90d under sterilized vs. non-sterile conditions and leached regularly with a dilute aqueous solution (0.05M CaCl2). Plant residue was added to soil (1:100, residue: soil, w/w) prior to the start of the incubation, but DOM was frequently applied to the soils along with each leaching experiment. The greater C and N concentration in the leachates of both sterilized residue-amended and DOM-amended soils compared to that of living soils, indicated a high microbial activity, as determined by CO2 loss, in the living soils. However, the proportion of the solubilized C (determined by 13C) from sterilized soils was largely comparable to that of living soils. This supports the recently suggested “regulatory gate” hypothesis, stating that solubilisation of OM largely occurs independent of the size or community structure of microorganisms. In addition, I observed that even with the presence of adequate amount of added fresh OM (ryegrass residue), about 70% of the solubilized C consistently originated from the humified soil OM, highlighting the role of native soil OM as the source of soluble OM in soil. In addition, in the DOM-amended soils, there was strong evidence, indicating that in the sterilized soils, the added DOM was exchanged with the humified soil OM as observed by an increase in SUVA, and humification index (HI) of the leached OM. Although the results of the study did not show a considerable difference in the solubilisation rate of added OM as a function of biological activity (either in the residue- or DOM-amended soils), there was clear evidence that the presence of microbial activity has resulted in further decomposition of the solubilised OM through biological transformations. Together, the results suggested that the proposed fractionation method can be used to separate two operationally defined pools of soluble OM with consistent differences in their size (C and N), properties (δ13C, SUVA254, and C/N ratio) and biodegradability across the land-uses and soil depth. The second part of the study supported the primary role of abiotic factors on the production of soluble OM from native soil OM. Although the abiotic mechanisms involved in the solubilization remain to be addressed by future studies. Cons and pros of the methods with some suggestions for further works have been mentioned in the last chapter.

Mudanças na taxa de acumulação e na natureza da matéria orgânica sedimentar, e suas relações com as variações climáticas e flutuações do nível relativo do mar durante os últimos 8.500 anos cal. A.P. foram investigadas em dois testemunhos provenientes do Saco de Ribeira, Enseada do Flamengo, e junto à praia do Lázaro, Enseada da Fortaleza, na região de Ubatuba, litoral norte do Estado de São Paulo. Para o estudo as amostras coletadas foram submetidas a diversas análises - granulometria, teor de CaCO3, teores de Carbono orgânico, Nitrogênio e Enxofre totais, e razões isotópicas de carbono. Datações 14C, calibradas para a idade calendário, permitiram estabelecer um modelo de idades para as variações sedimentares detectadas. Intervalos de clima mais quente, 8.000-6.000 anos cal. A.P., foram acompanhados de um aumento na taxa de acumulação de carbono T.A.C. (10-13 g m-2 ano-1), seguida de diminuição após 5.000 anos cal. A.P., para valores inferiores a 2 g m-2 ano-1. Variações climáticas regionais, possivelmente relacionadas a chuvas torrenciais, próximos ao máximo transgressivo, de 5.100 anos 14C A.P., foram detectadas pelo aumento nos valores de T.A.C. (10-12 g. m- 2 ano-1), aumento nas taxas de acumulação de massa (T.A.M.) e deposição de sedimentos mais grossos, acompanhados de aumento na tendência continental da natureza da matéria orgânica. As maiores tendências continentais da matéria orgânica sedimentar, registradas aproximadamente entre 1.500-1.200 anos cal. A.P., podem ser decorrentes de uma oscilação negativa do nível do mar. No geral, todos os resultados estão de acordo com as curvas de variação do nível relativo do mar, já descritas na literatura. As análises sedimentares da região estudada revelaram um evento regressivo-trangressivo, que ainda não havia sido referido para o Estado de São Paulo. A partir de ~2.000 anos cal. A.P., o mar teria atingido um nível mais baixo que o atual, com o mínimo provavelmente entre 1.500-1.200 anos cal. A.P., e encontra-se em ascensão até os dias atuais. As características anóxicas e a matéria orgânica sedimentar de origem planctônica registradas junto à praia do Lázaro, em meio a condições de energia relativamente mais alta, em ~900 anos cal. A.P., foram consideradas como resultado de condições óxicas das águas, acompanhadas de altas taxas de produtividade, e subseqüente degradação da matéria orgânica, existentes no período anterior. / Changes in the organic carbon accumulation rates (Corg A.R.) and organic matter source characteristics and their relation to climate and relative sea level changes during the last 8.500 cal. yr. B.P. were investigated in two sediment cores from 2 embayments - Flamengo and Fortaleza inlets - northern coast of São Paulo State. Sediment samples were analysed for grain size, organic Carbon, total Nitrogen and Sulphur contents, and ?13C ratio. Radiocarbon datings provided a model age to the sedimentary deposits. The warm climate interval 8.000-6.000 cal. yr. B.P. was accompanied by an increase in the Corg A.R. (10-13 g.m.-2 yr -1) and a decrease (~2 g.m.-2 yr -1) in the last ~5.000 cal. yr. B.P. Regional climate changes, as stormy weather, that may have ocurred near the maximum transgressive period called Santos Transgression at 5.100 yr. B.P., were recorded in the sedimentary profiles by relatively hight T.A.C. and T.A.M. values, coaser grain size sediment delivery, and enhanced terrestrial organic matter source characteristics. Improvement of terrestrial origin of the sedimentary organic matter recorded between 1.500-1.200 cal. yr. B.P in the studied area was mainly related to a negative sea-level oscillation. All the results are in general agreement with the existing sea level change curves. The sedimentary profiles suggest a negative sea-level fall event, that had\'nt been described yet for São Paulo State. It\'s proposed that the negative oscillation would have begun at ~2.000 cal. yr. B.P.and reached a minimum probably between 1.500-1200 cal. yr. B.P. The relative sea level has been rising since then. Anoxic conditions accompanied by algal origins of sedimentary organic matter, observed in the sedimentary profile from Fortaleza inlet at 900 cal. yr. B.P, during a more oxidizing environment are considered as a result of a previous well oxygencontaining water column and high productivity rates.

Colored dissolved organic matter (CDOM) is a part of total dissolved organic matter (DOM) and plays an important role in marine carbon cycling. Thus, a better description of the fates of CDOM may increase our understanding of DOM sources and sinks in marginal seas. This study aims to explore the distributions and possible controlling factors of DOM in the Taiwan Strait (TS) and the East China Sea (ECS) in the summer season. The TS is a marginal sea of interest as it receives freshwater from both Taiwan Island and Mainland China and it also connects water transports between ECS, South China Sea (SCS) and Kuroshio water (KW). The concentration of DOM is slightly higher in the western side (China coast) than in the eastern side (Taiwan coast), and the highest concentration is always found in the Minjiang plume, revealing a significant impact of river discharge. The absorption and fluorescence properties of CDOM varied to a large degree with space arisen from the mixing of source waters including freshwater (from Taiwan and Mainland China), Changjiang diluted water (CDW), SCS water and KW. The KW and river-plume waters (Changjiang, Minjiang) have the lowest and highest values for absorption coefficient (a(325)) and fluorescence intensity of terrestrial humic-like CDOM (Ft: Ex/Em= 320-360/420-460), respectively. Both a (325) and Ft correlated inversely with salinity. Although the spectral slope (S) varied only within a small range, it still can be used to differentiate water masses in TS, as the S value is generally lower in coastal waters than in SCS and KW. Meanwhile, Ft is highly correlated with surface DIN and Si in TS, showing that these parameters are strongly influenced by terrestrial inputs. There are six types of water masses mixing in the ECS in summer named CDW, Yellow Sea water (YSW), China coastal upwelling water, KW, Taiwan Strait Warm Current (TSWC) and Kuroshio upwelling water. Generally, the concentrations of DOC, DON and DOP are the highest in the surface water and decrease with depth due to strong degradation below the surface. The DOC/DOP and DOC/DON ratios of the most stations are higher than the Redfield ratio, showing a carbon enrichment of DOM in the ECS. The optical properties of CDOM show particular DOM characteristics in different water masses and reveal clearly the sources of DOM over various zones. After the operation of Tree-Gorges Dam, the CDW covering zone is likely reduced as reflected from the spatial patterns of salinity and absorption coefficient. The factor analysis implies that the terrestrial inputs and influence may be the dominant factor in constraining DOM and CDOM distributions in the TS and ECS.

Irrigation using reclaimed wastewater can introduce organic contaminants and dissolved organic matter (DOM) to soils. Sorption of three common organic wastewater contaminants to five soils of diverse organic matter composition was studied both before and after the removal of soil carbohydrate and peptide components using acid hydrolysis. Results suggest that these polar components may block organic contaminants from accessing higher affinity sorption sites in soil organic matter. The sorptive fractionation of DOM by three mineral soils was studied to assess the terrestrial fate of this complex environmental matrix. Carboxyl- and aromatic-containing moieties appear to preferentially and reversibly sorb to mineral soils. Conversely, carbohydrate and peptide components of DOM preferentially remain in the aqueous phase while aliphatic moieties were selectively retained only by a soil with high surface area. This thesis illustrates that reclaimed wastewater should be applied to soils cautiously as it may degrade soil and groundwater quality.

Irrigation using reclaimed wastewater can introduce organic contaminants and dissolved organic matter (DOM) to soils. Sorption of three common organic wastewater contaminants to five soils of diverse organic matter composition was studied both before and after the removal of soil carbohydrate and peptide components using acid hydrolysis. Results suggest that these polar components may block organic contaminants from accessing higher affinity sorption sites in soil organic matter. The sorptive fractionation of DOM by three mineral soils was studied to assess the terrestrial fate of this complex environmental matrix. Carboxyl- and aromatic-containing moieties appear to preferentially and reversibly sorb to mineral soils. Conversely, carbohydrate and peptide components of DOM preferentially remain in the aqueous phase while aliphatic moieties were selectively retained only by a soil with high surface area. This thesis illustrates that reclaimed wastewater should be applied to soils cautiously as it may degrade soil and groundwater quality.

Mudanças na taxa de acumulação e na natureza da matéria orgânica sedimentar, e suas relações com as variações climáticas e flutuações do nível relativo do mar durante os últimos 8.500 anos cal. A.P. foram investigadas em dois testemunhos provenientes do Saco de Ribeira, Enseada do Flamengo, e junto à praia do Lázaro, Enseada da Fortaleza, na região de Ubatuba, litoral norte do Estado de São Paulo. Para o estudo as amostras coletadas foram submetidas a diversas análises - granulometria, teor de CaCO3, teores de Carbono orgânico, Nitrogênio e Enxofre totais, e razões isotópicas de carbono. Datações 14C, calibradas para a idade calendário, permitiram estabelecer um modelo de idades para as variações sedimentares detectadas. Intervalos de clima mais quente, 8.000-6.000 anos cal. A.P., foram acompanhados de um aumento na taxa de acumulação de carbono T.A.C. (10-13 g m-2 ano-1), seguida de diminuição após 5.000 anos cal. A.P., para valores inferiores a 2 g m-2 ano-1. Variações climáticas regionais, possivelmente relacionadas a chuvas torrenciais, próximos ao máximo transgressivo, de 5.100 anos 14C A.P., foram detectadas pelo aumento nos valores de T.A.C. (10-12 g. m- 2 ano-1), aumento nas taxas de acumulação de massa (T.A.M.) e deposição de sedimentos mais grossos, acompanhados de aumento na tendência continental da natureza da matéria orgânica. As maiores tendências continentais da matéria orgânica sedimentar, registradas aproximadamente entre 1.500-1.200 anos cal. A.P., podem ser decorrentes de uma oscilação negativa do nível do mar. No geral, todos os resultados estão de acordo com as curvas de variação do nível relativo do mar, já descritas na literatura. As análises sedimentares da região estudada revelaram um evento regressivo-trangressivo, que ainda não havia sido referido para o Estado de São Paulo. A partir de ~2.000 anos cal. A.P., o mar teria atingido um nível mais baixo que o atual, com o mínimo provavelmente entre 1.500-1.200 anos cal. A.P., e encontra-se em ascensão até os dias atuais. As características anóxicas e a matéria orgânica sedimentar de origem planctônica registradas junto à praia do Lázaro, em meio a condições de energia relativamente mais alta, em ~900 anos cal. A.P., foram consideradas como resultado de condições óxicas das águas, acompanhadas de altas taxas de produtividade, e subseqüente degradação da matéria orgânica, existentes no período anterior. / Changes in the organic carbon accumulation rates (Corg A.R.) and organic matter source characteristics and their relation to climate and relative sea level changes during the last 8.500 cal. yr. B.P. were investigated in two sediment cores from 2 embayments - Flamengo and Fortaleza inlets - northern coast of São Paulo State. Sediment samples were analysed for grain size, organic Carbon, total Nitrogen and Sulphur contents, and ?13C ratio. Radiocarbon datings provided a model age to the sedimentary deposits. The warm climate interval 8.000-6.000 cal. yr. B.P. was accompanied by an increase in the Corg A.R. (10-13 g.m.-2 yr -1) and a decrease (~2 g.m.-2 yr -1) in the last ~5.000 cal. yr. B.P. Regional climate changes, as stormy weather, that may have ocurred near the maximum transgressive period called Santos Transgression at 5.100 yr. B.P., were recorded in the sedimentary profiles by relatively hight T.A.C. and T.A.M. values, coaser grain size sediment delivery, and enhanced terrestrial organic matter source characteristics. Improvement of terrestrial origin of the sedimentary organic matter recorded between 1.500-1.200 cal. yr. B.P in the studied area was mainly related to a negative sea-level oscillation. All the results are in general agreement with the existing sea level change curves. The sedimentary profiles suggest a negative sea-level fall event, that had\'nt been described yet for São Paulo State. It\'s proposed that the negative oscillation would have begun at ~2.000 cal. yr. B.P.and reached a minimum probably between 1.500-1200 cal. yr. B.P. The relative sea level has been rising since then. Anoxic conditions accompanied by algal origins of sedimentary organic matter, observed in the sedimentary profile from Fortaleza inlet at 900 cal. yr. B.P, during a more oxidizing environment are considered as a result of a previous well oxygencontaining water column and high productivity rates.

yes / NOM deteriorates water quality by forming taste, clarification, colour, and odour problems. It also increases coagulant and chlorine consumption which can initiate disinfection by-products harmful to human health. The coagulation-flocculation (CF) technique is an established method commonly employed to remove NOM in water treatment. Plant-based coagulant products (PCPs) derived from plants like the Moringa oleifera (MO) Strychnos potatorum Linn and Opuntia ficus indica, have been studied and proposed as sustainable alternatives to chemical coagulant, like, aluminium sulphate due to their abundant availability, low cost, low sludge volume and disposal cost, and biodegradability. This review paper provides an overview of the most widely studied plant-based coagulants and discusses their NOM and turbidity removal. It investigates recent analytical tools applied in their characterisation and floc morphological studies. The paper also investigates the effects of operating parameters such as coagulant dose, temperature, and pH, on NOM and turbidity removal. It also reviews up-to-date PCPs biophysical properties and CF mechanism and examines the efficiency of their extraction methods in reducing NOM. Finally, it discusses and suggests ways to overcome commercialisation draw-back caused by nutrient addition.

No description available.

Soil organic matter (SOM) is a critical biogeochemical pool that can be managed as part of global efforts to conserve nutrients and enhance carbon (C) sequestration. But reliably increasing SOM has proven difficult because most of the organic matter that enters soil as plant litter and organic amendments (i.e., compost, manure) is susceptible to decomposition by soil microorganisms and eventually is lost to the environment as greenhouse gases and non-point source pollution. Many soils lack the physical and/or chemical properties that enable some human-modified soils (e.g., terra preta soils in the Amazon Basin) to stabilize and retain C and nutrients in SOM while maintaining relatively high levels of productivity compared to surrounding natural soils that formed under similar conditions. I hypothesized that two of the major stabilizers of organic matter common to terra preta soils of the Amazon basin – black carbon (biochar) and poorly crystalline, reactive iron (Fe) minerals – could be applied to a fine-textured soil from Southwest Virginia to improve the accumulation and retention of C and nitrogen (N). I used a field experiment to compare the effects of three types of locally-produced biochars applied with and without an organic N fertilizer (blood meal) on soil C and N availability. I then used an incubation experiment featuring the soils from the aforementioned field experiment to examine the effects of applying Fe2+ -treated manure effluent on the retention of C and N in unamended and hardwood biochar-amended soils. I found that biochar adsorbed inorganic N in all cases, while providing a reliable, stable increase in SOM due to its recalcitrant nature. However, the manure effluent used in the incubation experiment stimulated the decomposition of mineral-associated organic matter (MAOM), with the addition of Fe2+ to the manure mitigating this apparent positive priming effect and the presence of biochar actually reversing this effect and promoting an increase in MAOM following manure application to biochar-amended soil. Overall, biochar stimulated the retention of N by decreasing the leachable inorganic N in the soil and enhanced soil C stocks. Additionally, biochar applications had the added benefit of promoting the accumulation of manure in soil as stable, microbially-processed MAOM, while co-applying Fe2+ with manure only served to inhibit the priming of native soil C. / Master of Science / Organic matter is an important constituent of all soils. Farmers and gardeners would like to increase the organic matter on their lands to improve their crop yields and health of their soils, yet people in many regions of the world struggle with actually getting long-lasting forms of organic matter to accumulate in soils. Moreover, managing soils to increase the amount of carbon stored in these long-lasting forms has the benefit of offsetting human contributions to atmospheric carbon dioxide and global warming. Some soils stabilize and build up organic matter more efficiently than others, and I hypothesized that if two well-known soil materials that help to stabilize organic matter – charcoal and iron – were added to a soil, then the accumulation of organic matter in the soil could be improved. The first part of my research was a field experiment in which three different kinds of charcoal were added either with or without an organic fertilizer to the soil in a Southwest Virginia pasture. I then measured the amount of carbon in the soil and determined that charcoal additions increased soil carbon and helped to retain mobile forms of plant nutrients. The second part of my research used the charcoal-treated and untreated soils from the field experiment for a project where cow manure was co-applied with three levels of iron and added to soils in jars in a controlled laboratory setting. The jars were then maintained at an ideal moisture and temperature for the growth of microbes for 70 days and analyzed afterwards. I found that the manure caused the organic matter in the soil to be consumed by microbes, while charcoal caused the organic matter from the manure to accumulate and remain. Adding iron with the manure prevented the microbes from consuming the pre-existing organic matter in the soil, but did not contribute to the retention of the manure in the soil. Overall, while both iron and charcoal influenced the retention of organic matter in soil, biochar proved to be more effective at stabilizing manure organic matter than the iron additions.

Doctor of Philosophy / Department of Agronomy / Dave Mengel / The Kansas State University Soil Testing Laboratory currently uses the Walkley-Black (WB) method for soil organic matter (SOM) estimations, the Shoemaker-Mclean-Pratt (SMP) buffer for lime recommendations, and bases the soybean phosphorus (P) critical value for P fertilizer recommendations off other crops. Hazardous waste is produced from WB and SMP creating a health hazard for workers, and substantial cost for handling and disposal. The substantial increase in land area devoted to soybean creates the need to validate currently assumed soil test P critical value and check the current P recommendations for that crop. Overarching objectives of this dissertation are to find suitable non-hazardous replacements for WB and SMP, and to find the soybean P critical value in Kansas. Three common methods used to estimate SOM are WB, dry combustion (DC), and loss on ignition (LOI). An experiment was set up using 98 Kansas soils to compare WB, scooped and weighed, LOI scooped, and DC weighed. All methods correlated well to each other with LOI to weighed WB, LOI to DC, and WB weighed to DC, having correlation coefficients of 0.97, 0.98, and 0.98, respectively. The lowest variability was observed with DC, followed by WB weighed, LOI, and then WB scooped with average standard deviations of 0.04, 0.13, 0.17, and 0.24, respectively. Two non-hazardous alternatives to the SMP buffer to determine soil lime requirement are the Sikora buffer, and the modified-Mehlich buffer. Sikora’s buffer is designed to mimic SMP. Buffer values alone or Mehlich’s equation may be used to calculate lime requirements. Thirty seven soils with a pH less than 5.8 were incubated at lime rates 0, 2240, 4480, 8960, and 17920 kg ECC ha[superscript]-1. Amount of lime required to reach pHs 6.0, 6.3, and 6.6 was calculated. Mehlich’s equation better predicted lime requirements for all target pHs and buffers than buffer pH alone. The Sikora buffer with Mehlich’s equation provided a better lime estimation than the Mehlich buffer using Mehlich’s equation. A P correlation and calibration study was conducted with soybeans at 23 sites in Eastern Kansas from 2011 to 2014. Soil Mehlich-3 P available P was compared to relative soybean yield at these sites. Soybean P critical value was found to be between 10 and 15 or 11.6 mg kg[superscript]-1 using Cate-Nelson, and linear-plateau models, respectively. A linear response to P and relative yield was observed on soils testing between 3 and 8 mg kg[superscript]-1, but not on higher testing soils.