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Mid-rotation fertilization and vegetation control are some of the most common silvicultural treatments in loblolly pine (Pinus taeda L.) plantations in the southeastern United States. Competing vegetation is commonly thought to sequester fertilizer nitrogen (N) and reduce the potential growth response to a mid-rotation fertilization treatment. This experiment aims to identify what proportion of applied N fertilizer is retained in the crop tree pine foliage, and the degree to which understory vegetation is competing for this resource. Our mid-rotation loblolly pine plantation received an application of 15N fertilization (urea 365 kg/ha, at 46% N by weight, i.e. 168 kg/ha of N) and a portion of plots received an understory vegetation control (basal spray application of triclopyr; 13.6% active ingredient) treatment either before fertilization or not at all. One-year post-fertilization, 15N contents within pine foliage, leaf fall/leaf litter, forest floor, and soil were measured, as was competing vegetation presence. There was significant variation in applied nitrogen acquisition among the different ecosystem components measured, with 0-15 cm soils retaining a majority at 32-37% added 15N. Differences in fertilizer N acquisition in pine foliage between plots with and without understory vegetation control was marginally significant (p = 0.06) with pine foliage in plots without understory vegetation capturing greater 15N (4.3% greater). Red maple (Acer rubrum) and oak species (Quercus spp.) were the most common competitors but neither had a uniquely pronounced effect on pine nitrogen sequestration. My data indicate that increasing competition reduces fertilizer N foliar concentrations in crop pine trees but at a modest rate and equally across species groups. An unrefined threshold determining when fertilizer N capture in crop pine trees was affected was found at 3.1 m2/ha of competing vegetation basal area. This site will continue to be monitored over time to assess fertilizer N retention in loblolly pine each year after fertilization and evaluate the fertilizer N capture within competing vegetation.

Applying fertilizers and deicers are two prevalent forms of property maintenance in the Midwest, however, these practices contribute to negative environmental impacts when applied incorrectly. While fertilizer use is well researched, deicer use on private properties is not. The objectives of this research are to 1) ascertain whether the patterns of fertilizer use are different from those of deicer in Hamilton County, Ohio and 2) determine what factors influence a resident’s decision to use these materials. Survey data was collected from 110 single family households (38.9% response rate) to determine fertilizer and deicer usage and perceptions. Respondents are motivated by property appearance to apply fertilizers. In contrast, deicer use stems from safety concerns. Respondents were significantly more likely to consider the environmental impact of fertilizers than deicers and to try to use fertilizers in an environmentally safe manner. Additionally, respondents reported that using deicers is a more neighborly practice while using fertilizers reflects more positively on them as members of their neighborhood. These findings highlight key differences between residential motivations of fertilizer and deicer application. Identifying these differences can contribute to the development of more effective educational and outreach programs to reduce the negative environmental impacts of fertilization and deicing.

Poultry litter (PL) is traditionally applied to no-till maize (Zea mays L.) cropping systems by surface broadcast. Poultry litter is nutrient dense, and it has been repeatedly shown that surface applied PL nitrogen (N) is vulnerable to losses to the atmosphere and nearby water systems. An application method was developed by USDA-Agricultural Research Service scientists for banding poultry litter (PL) below the soil surface with minimal soil disturbance to reduce ammonia (NH3) volatilization and surface run-off. It is well documented that subsurface applied poultry litter (PL) reduces N losses by ammonia (NH3) volatilization; however, the effect of this application method on N2O emissions and crop yields have been mixed. Nitrogen fertilization of agricultural soil stimulates nitrous oxide (N2O) production, a potent greenhouse gas, and accounts for over 75% of the anthropogenic N2O emissions globally. Best management practices for land application of animal manures as a source of N don’t primarily address the effect they have on N2O emissions. A two-year field experiment was initiated May 2014 on a Crider silt loam to determine if subsurface applying PL in multiple bands between maize (Zea mays L.) rows influenced N2O emissions, NH3 volatilization, nutrient use, and maize yield. Treatments consisted of an untreated control (UTC), urea ammonium nitrate (UAN, 32% N) surface banded (Fert), PL surface broadcast (PLBr), and three subsurface banded PL treatments. The subsurface PL treatments were 1 (PLSub1), 2 (PLSub2), and 3 (PLSub3) lateral bands in the inter-maize row area. Treatments receiving N amendments were added at 180 kg total N ha-1 each spring prior to maize planting. Nitrous oxide emission varied each growing season and N2O pulses coincided with rainfall events larger than 1-cm following treatment application. Subsurface banding PL had significantly lower (P < 0.1) cumulative N2O emissions than PLBr in 2014 and 2015 in at least some treatments. Surface broadcasting PL had greater NH3 volatilization than all PLSub treatments, which agrees with other studies. There were no differences between PLSub treatments in 2014 and 2015 for cumulative N2O emissions and NH3 volatilization. Nitrogen concentration in V4 maize aboveground dry matter was significantly higher in PLSub1 than PLSub2. Aboveground biomass yields for all PLSub treatments were greater than PLBr and similar to Fert. Subsurface PL application in 1 and 2 bands resulted in maize grain yields similar to Fert and significantly greater than PLBr and UTC when averaged across years. Few significant differences were observed in post-harvest soil sample nutrient concentrations between PLSub treatments. These results suggested that subsurface banding PL can reduce N2O emissions, conserve N, and increase no-till maize yields compared to the traditional method of surface broadcasting PL. Increasing the frequency of subsurface PL bands between maize rows did not clearly affect N2O emissions, nutrient conservation, or nutrient utilization by maize across the growing season.

Phosphorus (P) is an element that is crucial in many biological processes in all forms of life and is not substitutable. Excess P in wastewaters leading to the degradation of receiving waters or eutrophication once released is a major environmental concern. Removal of excess P from wastewater as the mineral struvite (MgNH4PO4·6H2O) could be a promising solution to reduce P discharge into receiving waters and can potentially provide a valuable fertilizer-P source for agricultural production. The objectives of this project were to evaluate the effects of: 1) chemically precipitated struvite (CPST), compared to triple superphosphate (TSP) and an unamended control (UC) treatment, and irrigation (irrigated and non-irrigated/dryland) on soybean [Glycine Max (L.) Merrill] and wheat (Triticum aestivum L.) response in a wheat-soybean, double-crop production system on a silt-loam soil (Aquic Fraglossudalf) in eastern Arkansas in 2018 and 2019 and 2) evaluate two struvite materials [electrochemically precipitated struvite (ECST) and CPST] relative to several other common fertilizer-P sources [TSP, monoammonium phosphate (MAP), diammonium phosphate (DAP), and RP] on the response of a pureline rice (Oryza sativa L.) cultivar grown under flood-irrigation in a P-deficient, silt-loam soil (Typic Glossaqualfs) and corn (Zea mays L.) and soybean grown in a P-deficient, silt-loam soil (Aquic Fraglossudalfs) in eastern Arkansas in 2019 and 2020. Aboveground dry matter, yield, and P, nitrogen, and magnesium tissue concentrations and uptake were measured. Results from the double-crop study showed that soybean seed yield were unaffected by fertilizer-P treatment and irrigation (P > 0.05), but differed between years (P < 0.01). Seed yield was 1.4 times greater in 2019 than in 2018 when averaged across irrigation and fertilizer-P treatments. In 2019, wheat yield did not differ (P > 0.05) among fertilizer-P sources. In 2019, rice grain yield did not differ (P > 0.05) among fertilizer-P sources. In 2020, rice yield was numerically largest from TSP (9.8 Mg ha-1), which did not differ from that from DAP, MAP, RP, and the UC, and was numerically smallest from ECST (8.2 Mg ha-1), which did not differ (P > 0.05) from that from CPST, and was lower (P < 0.05) than that from TSP, DAP, MAP, RP, and the UC. Averaged across years, corn yield from ECST was at least 1.2 times greater (P < 0.05) than that from CPST, TSP, MAP, DAP, RP, and UC. Soybean seed yield differed among fertilizer-P sources between years (P = 0.03). In 2019, seed yield was numerically largest from ECST (4.1 Mg ha-1), which did not differ from CPST, TSP, MAP, DAP, or RP, and was 1.2 times greater than that from UC. In 2020, soybean seed yield was numerically greatest from CPST (2.8 Mg ha-1) and numerically smallest from ECST (2.2 Mg ha-1). Results showed that wastewater-recovered struvite materials have the potential to be a viable, alternative fertilizer-P source for wheat-soybean, double-crop production system, flood-irrigated rice, and furrow-irrigated corn and soybean in P-deficient, silt-loam soils in eastern Arkansas.

Synthetic ammonia (NH3) used as fertilizer is essential for modern agriculture, but its production at present is fossil energy and emissions intensive. A more sustainable NH3 production alternative is to use renewable-derived electricity to obtain its precursors, specifically hydrogen (H2) from water electrolysis and nitrogen (N2) separated from air. The transformative impact of renewable NH3 is not limited to agriculture alone. Energy storage costs using NH3 are considerably lower than with H2or batteries, making it an ideal candidate for the high capacity, long duration seasonal energy storage necessitated by high fractions of renewables in the power generation mix. Internal combustion technologies which are well-developed for fossil fuel feedstocks can be easily modified to be fueled with NH3, allowing its use for controllable power generation or as a carbon neutral liquid fuel. Despite its promise, a number of challenges remain in realizing the full potential of this alternative paradigm. This thesis aims to collectively address some of these challenges through the use of mathematical optimization. The economics of small-scale renewable NH3 production for agriculture are analyzed and optimized at both the synthesis process and supply chain level. A flowsheet model is developed for optimal design and technoeconomic analysis of an absorbent-enhanced NH3 synthesis process which can reduce pressure and increase separation temperature, the main drivers of capital cost in traditional condenser-based synthesis process. Absorbent-enhanced process design optimization gives 30% lower capital costs and comparable energy efficiencies to the condenser-based process at production scales smaller than conventional by one to two orders of magnitude. Optimal deployment of this absorbent-enhanced process via wind-powered NH3 production modules in fertilizer supply chains makes renewable NH3 economically viable at approximately 25% lower conventional NH3 prices than if the traditional synthesis process is simply scaled down. The economic competitiveness of synergistic renewable NH3 production and utilization systems is maximized through combined optimal design and scheduling (CODS). These CODS models select and size the best technologies for given applications while simultaneously scheduling their operation to accommodate renewable intermittency. Performing CODS for wind-powered production of NH3 for use as fertilizer, agricultural fuel, and energy storage enabled 95% emissions reduction at a cost less than $20/tonCO2. Then, the optimal economics of H2- and NH3-based electrical energy storage were investigated for 15 locations throughout the continental U.S. which comprehensively represent its different climate-demand regions. Lowest cost systems in every location included both H2 and NH3 storage pathways and optimized the trade-off between H2's higher overall efficiency and NH3's lower storage cost. This hybrid energy storage concept was extended to combined heat and power systems in remote locations as a potential market for early adoption. Low cost, long term NH3 storage and subsequent power and heat cogeneration enabled fully renewable systems to be economically competitive with those that could purchase power and heat from conventional sources. Overall, the results of this thesis demonstrate the promise of renewable NH3 and the power of mathematical optimization in achieving its full potential.

Lead (Pb) speciation in soil is key for bioavailability assessment and exposure risk to humans from Pb contaminated soils. Soil ingestion is the main exposure pathway in Pb contaminated soils and in vitro bioaccessibility assays (IVBA) can predict relative bioavailable (RBA) Pb in soil by mimicking the GI tract conditions without traditional expensive animal feeding studies.In situ soil remediation has been considered an effective ecological treatment option compared to ex-situ techniques. The use of amendments such as biosolids, biochar, compost and phosphorous (P) amendments have been effective to decrease RBA in soils and, in doing so, reducing human exposure to the contaminant.In this study, soil amendments including biosolids, compost, wood-ash, biochar, soluble phosphate (SP) and their combinations were applied to Pb contaminated soil. Soil samples were incubated for up to 6 months at constant temperature, moisture and humidity. Samples were taken at three time points 1 (t1), 4 (t2) and 6 (t3) months of incubation and analyzed for total metal content, bioaccessible Pb (%IVBA-Pb), bioaccessible arsenic (%IVBA-As), organic carbon content (Org C), pH, extractable P and other key properties to determine the best treatment to reduce bioavailability of lead while improving soil health.Phosphorous was the most effective amendment to reduce %IVBA-Pb. Whether as individual or combined amendments, SP and biosolids resulted in 25-50% reductions of %IVBA Pb. Organic C addition did not reduce %IVBA-Pb, indicating complexation was not relevant for chemical immobilization of Pb in the case of strongly acidic soils such as the ones used in this experiment. %IVBA-As was correlated with pH and not P addition nor Organic C addition. Biosolid addition produced, apart from an expected plant available P increase, a great increase in Mineralizable Nitrogen content in the soils. Considering the importance of Nitrogen as an essential nutrient in plant growth, these results indicate that this amendment would be suitable for decreasing %IVBA-Pb and overall exposure to Pb contaminated soils. This is due to ensuring plant cover in the soils and decreasing soil erosion and loss, with the subsequent Pb dust dispersion, decreasing possible ingestion rates of the soil.

Nitrogen and a variety of other nutrients are necessary for proper crop growth and to maximize marketable harvest for farmers, though traditional fertilizer methods to supplement these nutrients are lacking. Inorganic fertilizer can have detrimental environmental effects, can be pricey, and can damage farmers’ soil over time. Brewer’s spent grain (BSG) is a protein-rich, food-safe byproduct of the brewing industry that is available nearly worldwide and may become available nitrogen after breaking down into soil. Five common farm crops were planted, treated with two rates of BSG as well as inorganic fertilizer, and harvested to compare the effects of BSG to fertilizer — to determine if BSG could be a viable alternative for farmers to supply their crops with nutrients. The marketable yield of the harvests was analyzed and revealed that inorganic fertilizer did not perform significantly better than BSG throughout the experiment, which was conducted over the course of multiple growing seasons.

Fall implementation of a rye (Secale cereale L.) cover crop (RCC) prior to spring corn (Zea mays L.) planting is a management practice used to improve soil conservation, water quality, and limit herbicide dependence. However, corn growth and yield following a RCC is often reduced due to early-season nitrogen (N) stress and decreased plant emergence, which can limit RCC adoption. The objective(s) of this research were to evaluate corn agronomic management practices (e.g., N and seeding rate management, in-furrow (IF) starter use) following a RCC and determine which management practices can be used to limit corn stress following a RCC and improve RCC adoption. Field studies were established at three locations in Kentucky between 2017 and 2020. Our results determined IF fertilizer and/or fungicide and an above optimum N fertilizer rate did not improve corn grain yield in any site-year, and no interaction between a RCC was observed. However, a split application (5x5 starter + V6 sidedress) of N fertilizer and an elevated corn seeding rate was observed to improve corn emergence, in-season plant health, and grain yield following a RCC. Overall, our results suggest farmers should look to terminate a RCC earlier (14 – 21d before planting), use a split N application, and increase corn seeding rates to limit potential N stress, plant stand reduction, and yield loss following a RCC.

An intensive production system is used to produce greenhouse floriculture crops, marketed for their flowers and attractive foliage. Chemical, environmental, and cultural methods are used to manage biotic and abiotic stresses during production. Additional tools are needed by growers because of growing concerns around the negative impact of plant production on humans and the environment. The objective of this research was to evaluate potential tools to improve floriculture crop resilience under stress during production and post-production.Botrytis cinerea causes disease in most major greenhouse crops and is resistant to several fungicides. Additional control methods, like plant growth promoting bacteria (PGPB) that can improve plant performance by increasing plant resilience to stress are needed. A collection of 60 bacterial strains was evaluated in a dual culture assay and an initial greenhouse trial with Petunia × hybrida `Carpet Red Bright’ to identify strains for the biocontrol of B. cinerea. Daily flower disease severity ratings were used to select seven strains that were evaluated in the validation greenhouse trial. Three Pseudomonas strains were selected for the greatest reduction in B. cinerea infection.The efficacy of PGPB and the plant’s susceptibility to B. cinerea were affected by fertilization. Petunia × hybrida `Carpet Red Bright’ was treated with bacteria or a commercial biocontrol product and fertilized with synthetic chemical or organic fertilizer at a low or high rate. Measured plant growth and flower disease severity revealed that plants with the high rate synthetic fertilizer were the largest and had the lowest disease severity. Reduction of disease severity varied between bacterial and fertilizer treatment combinations. Plants treated with one bacterium had reduced disease severity at the high rate synthetic chemical fertilizer but not at the low rate organic fertilizer.Specific fertility programs provide crops with needed macro and micronutrients, but overuse can lead to negative environmental impacts, plant disorders, and higher susceptibility to other stresses. Application of PGPB can improve floriculture plant performance grown under low fertility. Ninety-four bacterial isolates identified from the rhizosphere of ornamental plants were evaluated in P. hybrida `Picobella Blue’ grown under low fertility, and 15 isolates were selected for increasing plant performance. Whole-genome sequencing was used to determine their identity and bacteria were evaluated again under low fertility along with untreated plants receiving higher fertilizer rates. Three bacteria were selected as top performers for increases in flowering, vegetative health, and vegetative quality.Over- or under-watering is a common stress for Phalaenopsis orchids once the orchid reaches the consumer, but to avoid water stress, ice cube irrigation is recommended. Orchid health was evaluated after irrigation with either ice cubes or room temperature water. Orchids grown in bark media did not have a reduction in display life or health when irrigated with ice cubes.Utilizing novel tools, like PGPB or ice cube irrigation, during production or post-production is an important move toward improving floriculture crop performance. These tools can be used to improve floriculture crop resilience to biotic or abiotic stresses and establish additional sustainable practices for the greenhouse industry.

Urine diversion has been proposed as an approach for producing renewable fertilizers and reducing nutrient loads to wastewater treatment plants. Life cycle assessment was used to compare environmental impacts of the operations phase of urine diversion and fertilizer processing systems (via 1) a urine concentration alternative and 2) a struvite precipitation and ion exchange alternative) at a city scale to conventional systems. Scenarios in Vermont, Michigan, and Virginia were modeled, along with additional sensitivity analysis to understand the importance of key parameters, such as the electricity grid and wastewater treatment method. Both urine diversion technologies had better environmental performance than the conventional system, and led to reductions of 29-47% in greenhouse gas emissions, 26-41% in energy consumption, approximately half the freshwater consumption, and 25-64% in eutrophication, while acidification ranged between a 24% decrease to a 90% increase. In some situations wastewater treatment chemical requirements were eliminated. The environmental performance improvement was usually dependent on offsetting the production of synthetic fertilizers. This study suggests that urine diversion could be applied broadly as a strategy for both improving wastewater management and decarbonization.

The modern strawberry, Fragaria x ananassa Duch. is thought to have originated in France in the mid-18th century by the inadvertent crossing two American strawberry species, F. virginiana Duch. and F. chiloensis Linn. The large, sweet, and juicy fruit of F. ananassa quickly gained popularity in Europe, replacing the small, soft and fragrant woodland strawberry (F. vesca) in cultivation systems at that time. F. ananassa is easily propagated by runners, and lends itself well to perennial culture in temperate climates. Strawberries can be cultivated in a diversity of field systems, and grower recommendations for fertilizer, mulch, and pest management inputs vary by region as well as the market for which the grower is producing. In the northeastern region of the United States, strawberries are among the earliest-ripening crops in spring. Most strawberries grown in the Northeast are consumed locally, yet the majority of strawberries consumed is imported from other regions. Producing abundant, flavorful fruit can help strawberry growers attract and retain local customers. This thesis explores the factors that contribute to the development of sweet, juicy, and flavorful strawberries in Northeast production systems. Previous studies have connected chemical composition of strawberry to climate, soil nutrient status, soil microbiome, plant-pest interactions and field carbon inputs. My research evaluated variation in New York State-grown strawberry chemical composition from year-to-year, from farm-to-farm, and across nine different management practices on the same field site. I hypothesized that total soluble solids (TSS), titratable acidity (TA), and volatile profile of ‘Jewel’ strawberries would vary when grown at different sites, and that chemical composition of fruit would be affected by field management on the same growing site. I hypothesized that management-induced variation in fruit quality would have measurable effects on sensory qualities. Management practice was not associated with fruit quality traits: different levels of soil carbon inputs, N inputs, fertilization rate, and non-fertilizer inputs were not associated with the variation observed in TSS, TA, volatile profile, or phenolic content. A sensory evaluation found no perceptible differences in flavor or aroma of ‘Jewel’ grown under different management regimes. Only 3.4% and 3.0% of variation in TSS and TA, respectively, was associated with management practice. Yields were positively correlated with total N application in the form of urea, while organic forms of N were not significant predictors of yield. Managing strawberry fields for high yield did not result in reduced quality of fruits based on chemical composition or sensory panelist response. I found that all measured quality attributes can vary significantly from farm-to-farm, but year-to-year variation overwhelmed any differences from one growing site to the other. Seasonal GDD (base 14.3˚C) was weakly correlated with TSS and TA of fruit, but variation in aroma was not associated with local climate data. My findings suggest that year-to-year variation in chemical composition may be large enough to affect sensory perception. Between 2018 and 2019, the coefficient of variation from year-to-year was 70% for TSS and 49% for TA. Between 2019 and 2020, the coefficient of variation was 360% for TSS and 34% for TA. Average TSS observed in ‘Jewel’ samples from multiple farms changed from 6.32˚Bx in 2018, to 8.32˚Bx in 2019, and 7.90˚Bx in 2020. Average TA increased from 0.70 g/L-1 in 2018, to 1.65 g/L-1 in 2019, to 3.08 g/L-1 in 2020. By comparing the influence of conventional and organic management practices on ‘Jewel’ fruit quality, I conclude that N inputs are the most significant drivers of yields, but non-fertilizer inputs do not appear to affect quality characteristics of fruit including sweetness, acidity, phenolic content or aroma. Management practice was not significantly associated with fruit quality characteristics, sensory perception, percent marketable yield, or crown density of plants. Year-to-year variation in climate appears to be the most significant driver of ‘Jewel’ chemical composition and flavor attributes.

This thesis evaluates the profitability of a standard commercial inorganic fertilization practice vis-à-vis the following three alternative fertilization options: i) a broiler litter only fertilization scenario ii) a 2-tons per acre broiler litter annually plus supplementary commercial inorganic fertilization scenario, and iii) a 2-tons per acre broiler litter applied every other year plus supplementary commercial inorganic fertilizer. Furthermore, the likely environmental impact of each practice was evaluated. The representative farm is a 1,000-acre row crop farm in the Upper Coastal region of South Carolina, with a corn-wheat-soybean cropping sequence. Each cropping sequence required two years for completion, and a total of 5 sequences were evaluated for all four fertilization practices. The most profitable option evaluated was the broiler litter only fertilization practice. This option however, resulted in excess nutrients carry over especially for phosphorus over the 10-year study period. Moreover, findings are consistent with previous literature that a more profitable and environmentally efficient crop production level can be achieved by using a combination of broiler litter and commercial inorganic fertilizer. Mean NPV estimates for the four practices were compared, by evaluating their respective 95% confidence intervals and no statistically significant difference between the 2-tons per acre broiler litter annually plus supplementary commercial inorganic fertilization practice, and the 2-tons per acre broiler litter applied every other year plus supplementary commercial inorganic fertilizer was observed. The 2-ton broiler litter/acre on corn only and supplementary inorganic commercial fertilizer had the least nutrient carry-over over the 10-year study. All three proposed alternatives had better on-farm input cost efficiency compared to the standard commercial inorganic fertilizer only practice.

Abstract: Soil is an essential component supporting the growth and maintenance of terrestrial ecosystems such as forests, providing anchorage, water, and nutrients. In Canada’s boreal forest landscape, surface soils can differ widely in their chemical and physical conditions, ranging from coarse to fine textured mineral soils in the uplands to organic soils in the lowlands. Industrial disturbances in the boreal region require the salvage of surface- and sub-soils from low- and upland areas during open pit mine operations that are used in the reconstruction of soil profiles for forest reclamation. These materials are selectively salvaged and can be arranged in variable layers and thicknesses, which could have profound effects on early forest establishment. For the first project of my thesis, I compared the growth of trembling aspen (Populus tremuloides Michx.), jack pine (Pinus banksiana Lamb.), and white spruce (Picea glauca Moench.) on different reconstructed soil profiles using varying surface soil materials (salvaged lowland peat and upland forest floor material (FFM)), placement depths (10 or 30cm for peat, 10 or 20cm for FFM), and subsoil material types determined by salvage depth (Bm, BC, and C). Early seedling establishment and growth as well as soil and climatic parameters were monitored over a five-year period. Seedling growth was greatest on FFM and appeared to be related to phosphorous availability, while peat as a surface soil reduced growth, likely due to delayed soil warming in the spring and overall cooler soil conditions that potentially limited resource availability. However, the greater water holding capacity of the organic matter in peat provided a benefit for seedling growth that was apparent during water limiting climatic conditions. The underlying subsoil material influenced growth later in establishment when roots occupied the deeper subsoils. Aspen growth was greatest when the subsoil was shallow salvaged and represented a weathered subsoil (Bm) compared to the more deeply salvaged, less weathered subsoils BC and C. Aspen and pine seedlings, with their larger roots systems, may have benefited from small increases in the silt fraction of the subsoils that increased the water holding capacity of these otherwise coarse textured sandy soils. Spruce regeneration responded marginally to soil treatments because of its overall slow growth-strategy and tolerance to resource limitations. Based on the initial 5-year study, seedlings may have been limited by low phosphorus (P) and potassium (K) availability in the peat and the homogenized subsoil materials, while nitrogen (N) was readily available in the peat coversoil. Broadcast fertilization is a common method used to treat nutrient limitations on reclamation sites, supplying a wide range of nutrients to fulfill the varying requirements that are unique to each tree species; however, operational applications of NPK on organic soils often induce strong responses from unwanted colonizing vegetation, which reduces the nutritional benefits intended for the seedlings and could render the fertilizer application ineffective. A follow-up study was developed to test the use of a broadcast fertilizer application that targets specific nutrient deficiencies in the soil and in each tree species, while simultaneously reducing the response of competing vegetation. Liquid fertilizer was applied to six-year-old seedlings using five treatments in the field: Control (no fertilizer), NPK, PK, P, and K. Seedling growth, foliar nutrients, and vegetation cover as well as environmental parameters were measured over two growing seasons. Aspen responded the strongest to fertilization, particularly in the P treatment, while pine and spruce marginally responded to the NPK treatment; however, growth responses depended on the type of subsoil treatment. All three species had foliar P concentrations below their optimal levels in the Controls, while foliar N concentrations were low for both conifers. The competing vegetation increased in NPK and did not respond to the P, K and the Control treatments, indicating targeted fertilization reduced responses from colonizing competitors. Additional analyses of the soil conditions (e.g. pH, cation sorption, water availability, temperature) suggest that other factors were more limiting to the trees during the study, which reduced their responses to the fertilizer additions. Results from this thesis demonstrate how different strategies used for soil reconstruction and targeted fertilization can affect the performance of forest regeneration in post-mine areas, and boreal forest species responses may vary according to their ecological adaptations and the site conditions.

Smallholder agriculture in the developing world is subject to numerous risks and trends. This dissertation investigates the economic sustainability of mechanisms used by smallholder farmers to mitigate risk as they adapt to a changing environment. The first two essays focus on index-based drought insurance and its relationship to changing risk caused by climate change and the growth of rural microfinance programs. The third essay focuses on how smaller farm sizes due to rural population growth affect farmer incentives to invest in soil quality.The first essay utilizes a framed field experiment in Tanzania and a structural learning model to study how climate change affects the demand for index insurance programs. I find evidence that demand will likely not keep pace with rising premiums in the absence of subsidies, threatening the economic sustainability of these programs in areas of changing risk. The second essay utilizes an analytic theoretical model to study the interaction between index insurance and microfinance programs. I find that if premiums are sufficiently low, coupling index insurance and microfinance can help mitigate the moral hazard problem inherent in loan contracts. The third essay utilizes a theoretical model and a panel data set from Tanzania to test how decreased farm sizes caused by population growth affect investment in fertilizer and soil quality. I find that smaller farm sizes lead to greater fertilizer use, particularly for organic materials such as compost and manure, and an indeterminate effect on soil quality.

Abstract: Phosphorus is an essential element in several industries such as agriculture and a requirement for growth. Dwindling phosphate rock sources thus requires the security of new phosphorus sources to maintain future populations. On the other hand, wastewater contains a considerable amount of nutrients that are often released into the receiving environment. To reduce the eutrophication that results from effluent release and secure a new phosphorus source, nutrient recovery from treated wastewater can be an attractive option. Phosphorus and nitrogen recovery in the form of struvite (MgNH4PO4·6H2O) has been identified as a product easily precipitated from wastewater effluent and could help alleviate phosphorus pressures by acting as a slow release fertilizer. More specifically, anaerobic digestion of source-diverted blackwater has been shown to provide a good source for energy and nutrient recovery. However, since source-diverted blackwater lacks the dilution typically associated with municipal wastewater, the concentration of hazards would be expected to be much higher. Potential hazards of concern include microbial pathogens, antimicrobial resistance genes (ARGs), pharmaceuticals and heavy metals. Though struvite precipitation from wastewater is not a new process, the level of risk associated with applying recovered struvite to agriculture has not been well characterized. A full analysis of pilot and full scale struvite samples in comparison to lab produced struvite shows that all samples can be identified as struvite regardless of their source. However, further examination into the co-precipitation that occurs shows that a more complex matrix such as blackwater would produce a product with reduced purity as bacteria, viruses, ARGs and other macro- and micronutrients can be detected. Additionally, many water chemistry conditions have been identified as optimal conditions for enhancing the precipitation process, but the consideration of hazard co-precipitation has not been taken into account. This study shows that pH of 9, 1.5:1 Mg2+:PO43- molar ratio and MgCl2 dosing rate of 24 mL•min-1 are most optimal for enhanced phosphorus recovery and reduced co-precipitation from blackwater. Furthermore, it is shown that the post-processing methods, such as drying would be required to further reduce the risk presented by viable bacterial cells.

This thesis uses a mixed integer program to minimize the transport and storage cost of delivering spent microbial biomass (SMB), a bio-coproduct resulting from the production of 1,3-propanediol, to farm fields as a soil amendment and fertilizer substitute. The case study examines focuses on a bioprocessing facility and corn production in East Tennessee. The results indicate on-farm storage of SMB minimizes transport and storage costs of the material. A one percent decrease in the moisture content of SMB results in less than five percent decrease in the total transport and storage costs. Future research should investigate farmers' willingness to adopt the practice, cost sharing design, and to apply SMB to other crop production.

Irrigated land in South Carolina has increased at a rate of about 4,047 hectares per year over the past two decades. With this increase in irrigated land comes the ability to gain higher yields by applying nutrients through irrigation water. Therefore, many growers apply nutrients through irrigation systems, known as fertigation. On average, South Carolina growers apply approximately 100 kg/ha nitrogen (N) on cotton for a total of 32 million kg annually which totals $4.4 million annually. To stay competitive in the global market, it is increasingly important for growers to reduce crop input costs while maximizing yields. For example, a 20% reduction in N usage could save South Carolina cotton growers over $3.7 million annually. Applying proper fertilizer rates is a major management decision for Southeastern U.S. producers. In this region, considerable soil variation (texture and water holding capacity) and other major factors within production fields affect crop production including fertilizer management strategies. Therefore, uniform application of N fertilizer over the entire field in this region can be both costly and environmentally questionable. Several researchers have developed sensor-based algorithms and guidelines for variable-rate N management for this region. However, currently, there is no variable-rate fertigation equipment available to apply a correct amount of N where it is needed within a field through an overhead irrigation system. Therefore, the first goal of this study was to develop a variable-rate N application system that works independently of irrigation water flow and can be retrofitted onto an overhead irrigation system (conventional or variable-rate) for site-specific fertilizer application. The variable-rate fertigation system (VRFS) uses the pulse width modulation technique to apply precise rates of N based on prescription maps. The system is controlled by custom software developed at Clemson University, SC, USA. The application system closely followed design specifications and can apply different rates of N ranging from 0 to 135 kg/ha and could easily be retrofitted on an existing overhead irrigation system (uniform-rate or variable-rate). The VRFS was completely independent of the amount of irrigation water being applied to a location in a field and could apply fertilizers based on crop needs. The average application errors for the nozzle flow uniformity tests was 0.1%. The pulses with modulation results were promising with an overall average error of 1.8%. The system was capable of following prescription maps with an average N application rate error of less than 1.8% for all N rates. There was a strong correlation (R2 = 0.9996) between target and actual N application rates. Additionally, there are no practical decision-making tools available for variablerate application of N through overhead sprinkler irrigation systems, the predominant row crop irrigation system in South Carolina. Therefore, field tests were conducted on cotton (Gossypium hirsutum L.) during the 2016 and 2017 growing seasons to 1) adapt the Clemson sensor-based N recommendation algorithms from single side-dress application to multiple applications through an overhead irrigation system; 2) develop correlations between plants “Normalized Difference Vegetation Index” (NDVI) measured using a commercially available optical sensor (GreenSeeker®) and those measured by an unmanned aerial vehicle (UAV), and c) to compare sensor-based VRFS with conventional nutrient management methods in terms of N use efficiency (NUE) and crop responses on three soil types. Two seasons of testing Clemson’s N prediction calculation to apply multiple applications of N was very promising. The multiple applications of N compared to the growers’ method (even though much less N was applied) had no adverse impact on yields in either growing season. There was no difference in cotton yields between 101 and 135 kg/ha N applications in either management zone. Also, there were no differences in yield between sensor-based, multiple N applications and conventional N management techniques. In relation to comparisons of the sensor methods only applying N in three or four applications, statistically increased yields compared to single or split applications in 2016. Applying N in 4 applications, statistically increased yields compared to single, split or triple applications in 2017. When the sensor-based methods were compared to the growers’ methods averaged over four treatments the sensor-based N applications reduced fertilizer requirement by 69% in 2016 and 57% in 2017, compared to growers’ conventional method. When comparing N rates among the four sensor-based methods (three or four) applications, increased N rates by 22.41 kg/ha in 2016 and 25.77 kg/ha in 2017 compared to single or split applications but increased the cotton lint yields by 272.36 and 138.98 kg/ha, for 2016 and 2017, respectively. There was a positive correlation between the applied N rates and the leaf N concentration in cotton leaves. When more N was applied the more leaf N content was found in the plant’s leaves. However, this had no adverse impact on yields because the sensor-based methods applied significantly less N but three and four sensor-based applications yields were not significantly different from treatments that received 101 and 135 kg N/ha. Plant height was significantly less on the sensor-based methods compared to the growers practice. Statistically there was no difference in boll count between treatments 101 and 135 kg N/ha and four sensor-based N applications. Cotton biomass samples were collected and were not significantly different from any of the treatments. Utilizing an UAV to measure plant NDVI and subsequently calculate plant N requirements is promising. A drone was calibrated against ground based GreenSeeker® optical sensors. NDVI values measured with the sprayer-mounted GreenSeeker® were correlated with those measured using an UAV. There was a strong correlation between the GreenSeeker® and UAV.

Environmental contamination issues related to phosphorus (P) in surface waters substantiates the need to identify minimally-sufficient P fertilization amounts for production of containerized nursery crops and better understand the effect of routine amendments (i.e., dolomite [DL] and micronutrient fertilizer [MF]) added to pine bark substrates on chemical fate of P fertilizer. Four studies were conducted to accomplish two overarching objectives: 1) determine the minimum P fertilization amount and corresponding pore-water P concentration needed to achieve maximal growth of common containerized nursery crops and 2) determine the effect of DL and MF amendments in pine bark on P retention during irrigation and P fractions in substrate pore-water. In a fertigation, greenhouse study, calculated lowest P-fertilizer concentration that sustained maximal growth in Hydrangea paniculata ‘Limelight’ (panicle hydrangea) and Rhododendron ‘Karen’ (azalea) was 4.7 and 2.9 mg·L⁻¹ , respectively, and shoot growth Ilex crenata ‘Helleri’ (holly) was the same when fertilized with 0.5 to 6.0 mg·L⁻¹ P. Porewater P concentrations corresponding with treatments that sustained maximal growth of panicle hydrangea, azalea and holly were as low as 0.6, 2.2 and 0.08 mg·L⁻¹ P, respectively. In a separate study, utilizing low-P controlled-release fertilizers (CRFs), shoot growth of Hydrangea macrophylla ‘P11HM-11’ (bigleaf hydrangea) produced in two ecoregions was maximal when fertilized with as little as 0.3 g CRF-P per 3.8-L container, a 50% P reduction from the industrystandard CRF. Holly required 0.2 or 0.4 g CRF-P depending on ecoregion. Mean pore-water P concentrations that corresponded with highest SDW were 0.8 and 1.2 mg·L⁻¹ for hydrangea and holly, respectively. When irrigating fallow pine bark columns containing CRF for 48 d, amending pine bark with DL and MF reduced orthophosphate-P (OP-P) leachate concentrations by ≈ 70%, most of which was retained within the substrate. In a greenhouse study, containerized Lagerstroemia ‘Natchez’ (crape myrtle) were grown for 91 d in pine bark containing CRF. In pine bark amended with DL and MF, pore-water OP-P and total P concentrations, measured approximately weekly, were reduced by, on average, 64% and 58%, respectively. Total dry weight values of plants grown with DL plus MF or MF-only were 40% higher than those grown with no amendments; however, tissue P amounts and relative P uptake efficiency were the same among plants in these three treatments. Therefore, sorption of OP-P by DL and MF reduced water-extractable OP-P but did not limit P uptake by plants.

Nebraska has one of the largest agricultural economies in the United States and relies heavily on irrigation and fertilizer application to maintain crop yields. Over-irrigation and continuous application of nitrogen (N) in many areas has led to accumulation of nitrate-N in soils and sediments throughout the state’s vadose zone. Because nitrate-N is both persistent and mobile, groundwater concentrations in many areas of Nebraska and other agriculturally intensive states are increasing. Nitrate-N contamination of public and private drinking water supplies that utilize groundwater are of particular concern. Vadose zone sampling is an important method for rapidly assessing the effect of changing land use on potential groundwater contamination. In the current project, the occurrence and movement of nitrate-N was investigated using deep vadose zone soil cores collected from urban and irrigated farmland in the Hastings, NE Well Head Protection Area (WHPA) and compared to a previous study done at the same locations (R. Spalding & Toavs, 2011). Sampling previously collected sites allows for direct comparisons of current and historical nitrate-N profiles, potential movement, and can provide a method for evaluating effects of changing land use at the surface. Cumulative nitrate-N in the top 65 ft for urban irrigated lawns, pivot irrigated farmland, and gravity irrigated farmland had an average of 320, 540, and 700 total lbs-N/acre respectively. In farmland where irrigation changed from gravity to pivot application there was an average reduction of 170 lbs-N/acre in the top 55 ft of the profile over a five-year time span. This observation supports the use of sprinkler irrigation for more uniform water application, reducing potential leaching at the head and tail rows of gravity irrigated fields. While future studies are still needed, the importance of vadose zone monitoring in evaluating and protecting groundwater is beneficial in determining connections between surface activities and the underlying groundwater. Advisor: Daniel Snow

Best management practices (BMPs) are used in the nursery and greenhouse industry to increase production efficiency, and also serve to help meet clean water limitations on contaminants entering waters such as the Chesapeake Bay Watershed. Research is lacking on which BMPs are most widely used or most efficacious for Virginia nursery and greenhouse growers. Objectives of this work were to determine BMP use, barriers to adoption, and scientific efficacy. We conducted a survey of Virginia growers to find the 1) most widely used BMPs, 2) reasons behind BMP use, and 3) any barriers to BMP adoption. Sixty growers (17%) responded to the survey. The most widely used BMPs included irrigation scheduling, integrated pest management, optimized irrigation efficiency, plant need based watering, grouping plants by water needs, on-site water capture and collection, and use of controlled-release fertilizers (CRFs). Cost was a barrier to BMP adoption, and environmental concern was a commonly reported reason for BMP use. We documented the science supporting selected water-related BMPs (grass buffer strips, CRFs, and irrigation optimization BMPs). Providing the science supporting BMP use gives growers confidence in implementing BMPs to limit water contamination, and prevent waste.

Worldwide chemical fertilizer use has increased by four times during the last 50 years. Conventional agricultural systems have a high nitrifying nature, resulting in a loss of nearly 70% of overall nitrogen (N) fertilizer inputs, an estimated economic loss of $81 billion. Over application of fertilizer is rampant in tropical developing nations in Central America, where coffee is major crop. Agroforestry offers ecologically sustainable land management strategies that promote the provision of ecosystem services such as, protection of biodiversity, climate change mitigation, and water and soil regulation. When legume trees are incorporated as the shade tree in coffee production, direct inputs of nitrogen can occur. The specific objectives of this study were, (1) to quantify the effects of inorganic fertilizer and shade treatments on soil organic carbon (SOC), (2) measure and quantify the mineralization rates under inorganic fertilizer and shade treatments, (3) determine if the spatial abundance of ammonia oxidizing bacteria (AOB) is affected by varying shade management, or by inorganic fertilizer treatment, and 4) measure the effects of inorganic fertilizer application on the transfer of biologically fixed N by Erythrina poeppigiana to Coffea arabica in agroforestry systems in the region. The field study was conducted in Aquiares, Costa Rica. Chemical fertilizer was applied between four treatments at the rate of 0, 110, 170, and 230 kg N ha-1 yr-1 and coupled with three shade treatments (no shade, managed shade, full shade) defined by the management strategies of the legume tree E. poeppigiana. Analyses showed no significant difference in total SOC by fertilizer and shade treatments. Measured NH4+ µmol/L NH4+ and NO2- + NO3- µmol/L NO3- concentrations differed significantly by the shade treatment, but net nitrogen mineralization rates were not significantly different by fertilizer or shade treatment. A significant difference in dsDNA copy number of AOB per soil g-1 was determined by shade treatment. Finally, fertilizer treatment demonstrated a significant effect on the potential for biologically fixed nitrogen from E. poeppigiana to be transferred to coffee planted in association. Coffee agroforestry systems with full shade E. poeppigiana legume trees offered additional inputs of nitrogen to mitigate the use of chemical fertilizers.

In apple (Malus domestica Borkh.) orchards, rootstock genotype, and soil fertility management practices impact soil fertility, plant associated soil microbial communities, and orchard productivity. Apple growers select rootstocks to confer beneficial traits, including size control, precocity, and pest and disease resistance. Rootstock genotype may also influence microbial communities, resulting in changes that affect tree health and productivity. Many apple growers apply synthetic nitrogen fertilizers to improve fruit yield and quality. In excess of tree requirements, nitrogen fertilizers may reduce crop yield and quality, as well as contribute to water pollution. The addition of carbon-based amendments, such as yardwaste, chicken litter composts, and biochar, may potentially reduce nitrogen and water loss, while improving soil structure and mineral nutrient availability. Orchard and pot-in-pot experiments were designed to study the following objectives: 1) determine the effects of integrated carbon-based fertilizer amendments on tree growth, productivity, and orchard soil fertility, 2) assess the effects of biochar on tree growth, leaf mineral nutrition, soil physiochemistry, and microbial community structure and activity, and 3) understand how rootstocks and fertilizers alter soil microbial communities. Applications of composts, integrated compost-calcium nitrate fertilizers, and biochar increased soil carbon, organic matter, cation exchange capacity and microbial respiration. In the orchard study, nitrogen fertilizer application did not increase tree growth, fruit quality, or leaf nitrogen concentration. Biochar applied at high rates with nitrogen fertigation increased tree growth and leaf nitrogen concentration similar to nitrogen fertigation. In the pot-in-pot compost study, chicken litter compost increased tree growth, and integrated compost-calcium nitrate fertilizer applications increased leaf N concentration. Analysis of the microbial community structure of bulk soil samples from the biochar and compost pot-in-pot experiments determined that the community structure was similar for all treatments during the three-year study. Metagenomic sequencing of the rhizosphere bacterial community indicated that compost applications altered community diversity and evenness, and that compost treatments were more similar to each other than to the calcium nitrate treatment. Data from my dissertation research suggests that compost can be used to increase orchard soil fertility, tree growth, and leaf nutrition, and that compost applications increase soil microbial community diversity and activity.

Abstract: Poor quality cover soil, a lack of propagules, and availability of suitable microsites can be serious challenges in the re-vegetation success of surface mines. In my thesis research, I examined the response of total cover, species richness and community composition of colonizing vegetation on a harsh coal mine reclamation site in Alberta, Canada to the presence of planted aspen seedlings and amendment with biochar and fertilizer. Additionally, I explored the effects of shelter type (wood vs. brick), along with the effects of aspect and distance from shelter on survival and growth of four seeded native species and on density of volunteer vegetation. Results suggested planted aspen seedlings and fertilizer increased both cover and richness of colonizing vegetation in the first growing season, but increasing the amount of fertilizer did not result in additional effects. The application of biochar did not influence the cover of colonizing vegetation but did result in decreased richness; no synergistic effects of biochar and fertilizer were found. The provision of shelter generally improved survival of seeded species and density of volunteer species although effects differed somewhat among species and with aspect and distance from shelter. Lastly, within the short timeframe of this study there was no clear evidence that either type of shelter was preferable. These findings emphasize the importance of planting aspen, amending with use of fertilizer and using shelter as means to improve poor cover soil quality, create suitable microsites and encourage natural re-vegetation on challenging reclamation sites. Continued research regarding biochar use and its combined effects with fertilizer on poor substrates is needed.

Synthetic fertilizers are significant drivers of the environmental impacts of agriculture. For farms located near water bodies, algal products are promising organic soil amendments. In the Kaneohe Bay watershed on Oahu, Hawaii, efforts are underway to mitigate harmful marine algal growth and repurpose the invasive seaweed as a local resource. Gracilaria salicornia is a common invasive algal species found in Kaneohe Bay and around the world. This species is a potential potassium fertilizer source, but requires high application rates leading to time intensive and difficult labor for farmers. This study evaluated the use of G. salicornia as a soil amendment at lower application rates than those required to provide complete plant nutrition to determine whether G. salicornia increases pak choy growth and the efficiency of fish bone meal fertilizer. This study also evaluated the use of a liquid amendment from G. salicornia that had been anaerobically digested, a processing method that farmers are considering in order to obtain methane fuel while retaining most of the nutrients in a liquid by-product. Pak choy yields were positively correlated with fresh G. salicoria application when paired with a low fertilizer rate, and G. salicoria application rate was correlated with increased tissue concentrations of nitrogen at high fertilizer levels; however, these effects were only observed on one of the two soil types used.Ethnographic methods were used to study the diversity of farm types in the Kaneohe Bay watershed and analyze the challenges and opportunities that farmers and community members might face in increasing the use of the invasive algae. I used interviews and participant observation with farmers to determine the potential impacts of adopting algal amendments on labor patterns, nutrient sources and efficiency, soil health practices, and productivity. The study showed that if the algae removal programs continue, they could provide a substantial portion of the potassium needs for organic farms in the area. Conventional growers were less interested in the fresh algae as a source of potassium, as it would increase their labor requirements, but both conventional and organic growers were interested in composted algae to improve their soil organic matter, and liquid anaerobic digestate as a soluble fertilizer. Farmers must adapt particular inputs to create value within their individual circumstances and find ways to coordinate their efforts from different social positions, but diversity can also enhance learning by broadening the scope of informal experimentation among a variety of crop types and management styles. Participatory research and community-based non-profit organizations showed potential for facilitating the spread and adaptation of organic inputs and practices via farmer-to-farmer exchange of information, and for building relationships with outside expertise and resources.

Current global agricultural production is completed with little regards to sustainable soil use. It is clear that the research and use of sustainable management practices must be expanded in order to preserve this natural resource. The objectives of this research were to focus on improving soil fertility and resource use efficiency by 1) evaluating farm management practices to find those that conserve soil and improve yields, 2) looking at alternative methods of fertilizing through the reuse of waste materials in agriculture. The last objective was to 3) test a more efficient method data collection and research production, resulting in more rapid outreach and use of sustainable methods. A study initiated in May 2015 in Ohio compared no-till (NT) and tillage (T) management practices by examining the release of preserved nitrogen (N) from a soil that has been under long-term no-till corn and soybean production. Crop N sufficiency and yields from the T and NT treatments were compared at varying urea application rates. The results showed that the T whole plot consistently provided higher N uptake, crop productivity, and yields when compared to the NT whole plot, but results may have been influenced by unusually high rainfall following fertilizer application. A study initiated in May 2015 in Tennessee tested the use of an industrial byproduct, spent microbial biomass (SMB) as a potential N source for corn. The biomass was compared at varying rates to the current farmer urea application rate. Nitrogen availability and crop uptake was compared within the treatments and no significant differences between the urea treatment and SMB treatment yields were found, indicating that SMB could offer a sufficient source of N in local corn production. To improve efficiency in corn research and data collection, a reduced effort hand-harvest method was compared to the currently accepted method in the Ohio and Tennessee studies. Yields extrapolated using the ten plant harvest method and the current hand harvest method were not found to be significantly different in either study (p>0.05). These results indicate the potential use of this method in future maize studies to improve project efficiency and increase research production.

Phosphorus (P) is a key limiting nutrient for soybean production in South Dakota. Soil tests have been used as a baseline indicator for plant available P and fertilizer recommendations for over a century. Plant nutrient analysis may be used to complement a soil test as a way to validate fertilizer and management practices. Soybean nutrient sufficiency ranges have only been slightly adjusted since they were published in the 1960’s. The objectives of this study were to update the soil test P and soybean plant P sufficiency level in South Dakota and to recognize implications of improper plant sampling. We also wanted to differentiate between nutrient concentration and nutrient uptake. A randomized complete block design was used for this experiment in Eastern South Dakota at eleven locations in 2013, and ten locations in 2014. Triple Super Phosphate (TSP)-fertilizer treatments were broadcast applied at the following rates: 0, 22, 45, 67, 90 kg P2O5 ha-1. Data collected included pre-plant soil samples, plant tissue samples at V4, R2 and R6.5 growth stages. In addition, grain samples and yield was measured. Tissue samples were analyzed for total P and soil samples were analyzed for Olsen, Bray-P1 and Mehlich 3 P. There were no significant differences in yield across locations in either year of the study. Grain P concentration increased at higher P rates. Failing to remove the petiole diluted trifoliolate P concentration by 15 to 18% . Improper plant sampling methods result in inaccurate nutrient data to make management decisions with. Fertilizer recommendations should be reevaluated with economic optimum in mind.

Nitrogen (N) is a vital factor of corn (Zea mays) production. Previous work in South Dakota has shown that there is uncertainty as to whether nitrogen requirements are the same for corn raised under no-till (NT) versus conventional till (CT) production systems. The objective of this study was to evaluate whether N requirements continue to be greater under long-term NT versus CT production systems in southeastern South Dakota, while also considering effects from cover crops and crop rotation. This was a two year study conducted at the SDSU Southeast Research Farm near Beresford, SD; it was superimposed on a long-term rotation and tillage study established in 1991. Treatments included applied N rates of 0, 40, 80, 120, 160, and 200 lbs N acre-1. Rotations were: corn/soybean (Glycine max) and corn/soybean/small grain; the three-year rotation was split additionally by ‘cover crop’ and ‘no cover crop’ treatments. Parameters measured included: soil plant analysis development (SPAD) chlorophyll readings, normalized difference vegetation index (NDVI) readings, ear leaf N content, total plant N uptake, yield, test weight, moisture, and grain protein. In 2014 small plot results were quite variable due to 13.5” of rainfall in June; the 2015 growing season was mild, producing more representative yields. Both N rate and tillage showed significant impacts on yield in the 2014 and 2015 three-year rotation. In 2014, spring soil nitrate levels tended to be 50 lbs ac-1 less in the ‘cover crop’ verses ‘no cover crop’ treatments, but there were no significant yield differences between cover crop treatments. Nitrogen that was not available in the spring likely became available later when cover crop residue decomposed. No-till corn was generally more sensitive to N application in the 2015 two-year rotation than CT corn, however, optimum N rates were the same across tillage regimes. In this study, long-term NT soils did not consistently require more N than CT soils. More research needs to be conducted to further define N recommendations and the impact of cover crops and crop rotation on soil N credits.

Abstract: Initial reclamation practices affect the early development and future recovery trajectories of tree and understory species on reclamation sites. In this thesis I explored the effects of yellow sweet clover (Melilotus officinalis) as a cover crop on tree performance and competition control in forest floor material which was salvaged and directly placed at two different depths (15 cm and 40 cm). Sweet clover supressed the establishment of some competing species; however total vegetation cover was not impacted and total mortality of planted Populus tremuloides, Pinus contorta, and Picea glauca seedlings was greater in sweet clover plots. Tree seedlings had better annual growth and lower mortality in the 40 cm salvage and placement depth treatment, potentially due to a more diluted seed bank which decreased dominance of competitive species. In a second study, I assessed the impact of four fertilizer treatments (control, 250 kg/ha immediately available fertilizer (IAF), 500 kg/ha IAF, and 670 kg/ha controlled release fertilizer) applied to two different capping materials (forest floor material (FFM) and a peat-mineral mix (PMM)) on initial forest vegetation development. The application of fertilizer did not affect average species richness in either capping material; however fertilization promoted increased cover of grasses in the FFM. Over time the number of annuals/biennials as well as non-native species decreased in both capping materials and the number of desirable forest understory species increased in the FFM.

Fertilizer is a major limiting factor to agriculture in southern Africa (SA). Coupled with this is lack of appropriate fertilizer recommendation rates for high productivity in existing agricultural systems. Field experiments were conducted to determine nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates for high cassava tuber yield and quality for the coastal semiarid Dondo District of Mozambique, and high maize grain yields for both vertisol and inceptisol of Maphutseng in Lesotho. In general, the results showed that cassava tuber yield, cassava tuber quality as measured by tuber starch content, and maize grain yield were significantly increased by fertilizer addition (p0.05). The results also showed that maize grain yield was not significantly affected by tillage practices (p>0.05). Combined applications of 60 kg N-60 kg P-0 kg K and 60 kg N-90 kg P-150 kg K kg per ha are suggested for high cassava tuber yield, and high cassava tuber starch content for the coastal semiarid Dondo District of Mozambique, respectively. Economically optimum maize grain yields (EOY) and profits (EOP) for the southwest lowlands of Maphutseng village, Mohale’s Hoek District, Lesotho, were estimated at 222 kg, 182 kg, and 123 kg of N (applied as limestone ammonium nitrate) per ha for no-till vertisol, no-till inceptisol, and till vertisol maize systems, respectively. The results suggest that an application of 30 kg of P (P2O5) per ha is required for high grain yields in inceptisol maize system. The results also confirmed that the benefits of not tilling the soil are not immediate. On the whole, the results suggest that there is potential to increase productivity in existing agricultural systems with the use of fertilizer in both Mozambique and Lesotho. However, this will not be possible without increasing farmers’ access to fertilizer given that fertilizer use in both countries is still very low (< 20 kg per ha).

Soil testing methods such as the Illinois Soil Nitrogen Test (ISNT) and Direct Steam Distillation (DSD) have been developed which measure alkaline hydrolyzable-N (AH-N) as a means of estimating potentially mineralizable-N. Crop residues play an important role in N cycling. However, the ability of the ISNT and DSD methods to determine AH-N within crop residues is unknown. Therefore, the first objective of this study was to determine the ability of the ISNT and DSD to quantify potentially mineralizable-N within five different crop residues common to Arkansas. Corn (Zea mays L.), soybean (Glycine max, L.), wheat, rice (Oryza sativa, L.), and grain sorghum (Sorghum bicolor, L.) residues were labeled with 15N using 10 atom% 15N labeled-urea. A 0.2 g subsample of residue was subjected to both the DSD and ISNT. Hydrolyzed-N was captured and analyzed for atom % 15N to compare fertilizer atom % 15N to that of the original residue. Total N was quantified to establish percent recovery. Analysis of variance for percent N recovery showed a significant residue by method interaction (p

The use of soil fumigation for nematode management in cotton (Gossypium hirsutum) has become increasingly popular in recent years in the absence of effective resistant cultivars. While soil fumigation is relatively expensive, lint yields have consistently been improved to make this practice profitable in fields with severe nematode pressure. Growers in southern Arkansas have observed changes in cotton growth patterns when severely infested fields are fumigated. The most noticeable change has been excessive (rank) growth resulting in an increased need for growth regulators, especially where the nitrogen fertilization exceeds standard recommendations. Field studies were conducted between 2007 and 2010 to determine if these changes in crop growth are related to nematode control or nitrogen fertilizer rates alone or in combination. Large plot studies were conducted in a field with a history of root-knot nematode (2007) or reniform nematode pressure in (2008 - 2009) consisting of twelve row strips that had received Telone II® (1,3-dichloropropene) paired with equivalent sized strips that received no fumigation. Within these strips five nitrogen rates (34, 101, 123, 146, and 224 kg N/ha) were applied in 30 m long plots. In 2009 and 2010, microplot studies were also conducted in the reniform location. Six row strips that had received Telone II® at 28 l/ha were paired with equivalent sized strips that received no fumigation. Within each strip, three nitrogen rates (0, 101, 146 kg N/ha) were applied in 3 m long plots. Results show yearly variability due to nematicide application and suggest that maintaining fertility is beneficial whether or not nematodes are controlled. Excess growth above normal cotton parameters was not observed due to the inputs.

Nutrient pollution as a result of excessive fertilizer application is of major concern for Florida's water resources. Excess fertilizer can be lost either via surface runoff or by leaching through the soil mass eventually reaching water bodies and leading to eutrophication. The focus of this study is to analyze the effect of low rainfall intensities and overland flow from an adjacent roadway surface on the loss of nutrients from two different fertilizers. This study focuses on the fate of the nitrogen and phosphorus present in fertilizers utilized by the Florida Department of Transportation for the stabilization of highway embankments. This research was performed on a field-scale test bed and rainfall simulator located at the Stormwater Management Academy at the University of Central Florida. The loss of nutrients was measured from two soil and sod combinations typically found in Florida and used for highway stabilization -Pensacola Bahia on AASHTO A-2-4 soil and Argentine Bahia on AASHTO A-3 soil. Two different fertilizers were analyzed, an all-purpose, quick-release 10-10-10 (N-P-K) fertilizer previously used by FDOT, and the new slow-release 16-0-8 (N-P-K) fertilizer, both applied at a rate of 0.5 lb/1000 ft2 consistent with FDOT's practice. Each combination was analyzed under two rainfall intensities: 0.1 in/hr and 0.25 in/hr at a slope consistent with typical highway cross-sections found in Florida. Nutrient losses were measured by collection of runoff and/or baseflow that escaped the test bed. Additionally, from the soil samples collected throughout the testing period, the mass of the nutrients was compared to the mass balances values based on literature from a previous study on fertilizers performed at the Stormwater Management Academy. The experimental findings of this study showed that there was a reduction in total nitrogen and total phosphorus on both A-2-4 soil and A-3 soil at the 0.25 in/hr intensity as a result of switching to the slow-release 16-0-8 (N-P-K) fertilizer. Results from the 0.1 in/hr rainfall intensity, which were available only for the A-2-4 soil, showed that at this intensity there was no apparent benefit to the switch in fertilizers. Furthermore, it was found that less total nitrogen and total phosphorus was lost from A-3 soil than A-2-4 soil at 0.25 in/hr when using 10-10-10 (N-P-K). At 0.1 in/hr, there was no apparent difference in total nitrogen lost. However, less total phosphorus was lost at this intensity. The results of this study showed that there is an environmental benefit to applying slow-release fertilizers. This was more significant for the 0.25 in/hr intensity than the 0.1 in/hr intensity at which no apparent benefit was found. In addition, it was found that runoff was a greater source of nutrient loss than baseflow, although baseflow losses were substantial. Furthermore, it was found that total nitrogen tends to be lost via both pathways of runoff and baseflow while phosphorus has a lower tendency to leach through the soil but readily runs off the soil surface. It was also observed that because fresh sod tends to be heavily fertilized, applications of fertilizer could be reduced or avoided entirely after sod placement and applied as needed.

Intensification of agricultural management has allowed substantial increases in food production on existing agricultural lands, but with major global environmental costs. This dissertation explores the global-scale possibilities and tradeoffs associated with agricultural intensification using spatial data analysis and modeling. In Chapter 2, we analyze intensification opportunities from closing yield gaps, and find that large production increases (45% to 70% for most crops) are possible. We also examine what changes to management practices may be necessary to close these yield gaps, and find these vary considerably by region and current management intensity. A sub-national, crop-specific dataset of cropland nutrient use was developed to support this analysis. Chapter 3 focuses on intensification potential in the context of climate change. We find that a moderate yield gap closure scenario could result in net yield increases across much of the globe, even in the context of circa 2050 climate change. However, the capacity for intensification to overcome climate impacts erodes considerably under uniform global temperature increases of 4-5°C. Chapter 4 examines the opportunity space for improved nitrogen (N) management. We find that a reallocation of spatial N use intensity could achieve current cereal production with ~50% less N application and ~60% less excess N. We quantify a tradeoff frontier for nitrogen use and cereal production, and discuss the potential for efficiency improvements to push the frontier forward. This dissertation highlights the importance of improving agricultural management across the globe to meet food security and environmental goals.

Soybean cyst nematode (SCN), Heterodera glycines, is the major yield-limiting pathogen on soybean and various plant-parasitic nematodes can damage corn. Additionally, the nematode community is a useful bioindicator for soil health. In chapter 1, relevant research is reviewed. Chapter 2 describes experiments testing ten organic soil amendments at various rates for SCN control in the greenhouse. Some amendments-particularly canola meal, pennycress seed powder and condensed distiller's solubles-effectively reduced SCN populations at 40 days after planting soybeans. By 70 days after planting, SCN control by amendments was diminished. Additionally, phytotoxicity was a concern, particularly at 40 days after planting. Based on these experiments, organic soil amendments have value for SCN management, but more work is needed to optimize amendment efficacy particularly at the field scale. Chapter 3 describes the impact of tillage, granular nematicide (aldicarb or terbufos), synthetic fertilizers (NPKS combinations), and organic fertilizer (swine manure) on plant-parasitic nematodes, the nematode community, and plant yield as assessed in a corn-soybean cropping system. H. glycines, Helicotylenchus spp, Xiphinema spp, and Pratylenchus spp were the major plant-parasitic nematodes present at the sites. Tillage had only minor impacts on populations of major plant-parasitic nematode genera. While aldicarb reduced H. glycines and Helicotylenchus populations, albeit inconsistently, terbufos did not affect major plant-parasitic nematode populations. Nematicides increased soybean and corn yields under some conditions suggesting plant-parasitic nematodes impacted corn and soybean, although this impact was inconsistent. Tillage, fertilizer, and nematicide impacts on the nematode community were often site- and season-specific. Manure application compellingly shifted the nematode community to one of increased enrichment and decreased community structure. The inorganic fertilizers had minimal impact on the nematode community. Conventional tillage decreased nematode community structure based on some measures, but increased bacterivore and fungivore population densities. In contrast, aldicarb nematicide decreased bacterivore and fungivore population densities. Effects of terbufos nematicide on nematode populations and community composition were inconsistent.

Effects of media, soil moisture, fertility rate, and plant growth regulators on plant growth were investigated for 13 taxa of succulents. Media: Liners were grown in five common greenhouse substrates: 80% peat, 60% bark + 30% peat moss, 80% pine bark/20% Permatil (v/v), 100% composted pine bark, or whole tree substrate until market ready. Overall, higher percentage bark mixes yielded smaller plants, with lower shoot dry weights, shoot heights and widths. Soil Moisture: Liners were potted into a 60% bark/30% peat soilless potting mix. In group 1 , irrigation to container capacity occurred when volumetric soil moisture content fell below 30%, 20%, or 10%,. Group two (seven species) irrigation thresholds were shifted to 35%, 25%, and 15%. Effects of irrigation rate were significant in three of the 13 species studied, and those effects were species-specific. Fertility Rate: Liners were potted into60% bark/30% peat substrate. Fertility reatments in group were 0, 50, 100, or 200 mg.L-1 nitrogen. Group 2 plants received treatments of 50, 150, 250, or 350 mg.L-1 nitrogen. Four of the 11 species studied were affected by nitrogen rate, with rates up to 200 mg.L-1 generally producing the largest plants. PGRs: Seven species were potted into a 60% bark/30% peat substrate. Group one plants were treated with a foliar application of benzyladenine (Configure) at rates of 0, 400, 800, or 1600 mg.L-1. Group 2 plants were treated either BA at 0, 250, 500, or 1000 mg.L-1, dikegulac sodium (Augeo) at 400, 800, or 1600 mg.L-1, or a tank mix of 500 mg.L-1 Configure and 800 mg.L-1 Augeo. BA caused an increase in branches leaders or offsets in two species.

Field studies examined the strategies of mowing, herbicide, fertility, and all combinations on tall ironweed populations, weed biomass, pasture yield, grazing, economics, and forage quality at three Kentucky locations. Mowing was performed in July 2008 and 2009, herbicide applied in August 2008, and fertilizer applied in September 2008 and 2009 at all locations. Weed populations were measured in 2008, 2009, and 2010, and forage and weed biomass collected in May or June of 2009 and 2010. Herbicide treatments reduced weed biomass at all locations, and reduced tall ironweed stems by 64% or greater in 2009 at all locations. Weed biomass did not differ when comparing all treatments with and without mowing or treatments with or without fertilizer. Forage grass biomass produced was greatest with herbicide plus fertilizer and with the combination of mowing plus herbicide plus fertilizer at all locations in both years. Two years of grazing did not reduce weed populations. Grazing did reduce forage grass and clover biomass at one location, and weed biomass at two locations. Two locations had positive economic returns based on herbicide treatment for weed control and forge yield. Herbicide treatments reduced crude protein at one location and in-vitro true digestibility at two locations.

A fertility study conducted comparing organic nitrogen versus synthetic nitrogen on yield, quality, mineral and phyto-nutrient content of sweet corn under conventional cultural practices.

Despite the urgency of reducing the environmental impacts of food production, the public and private sector continues to promote intensive agriculture methods. Studies show that input substitution strategies have led small-scale farmers into a cycle of debt and degraded soil fertility. In Thailand, non-governmental organizations have assisted farmers through organic extension programs. This research examined the socio-ecological benefits of organic production to rice farmers through a mixed methods approach. Coding and categorizing of semi-structured interviews with 50 Northeastern Thai organic farmers’ sheds light on shared values, perceptions, and actions towards nature. Through grounded theory I discovered the salience of fertilizing practices as a medium of associations between farmers and nature. A subsequent phase of structured interviews with 75 members of organic farmer groups investigated the ways that informants improved soil fertility. Organic farmers perceived bountiful rice and good health as externalities of nurturing the soil. By engaging in organic fertilizer practices respondents came to see themselves as part of an extended community of life. Data analysis reveals that participation in fertilizer groups contributes to improved health, wellbeing, and the long-term sustainability of organic farms.

Container grown perennials are a popular product offered by nurseries and greenhouses and included in their production but little research has been reported on proper overwintering techniques for herbaceous perennials and ornamental grasses. In the first experiment rooted liners of Pennisetum alopecuroides, Pennisetum "Hameln" and Pennisetum "Little Bunny," were potted. Treatments included, utilizing two overwintering covers, two fertilizer rates (low or high) and two substrate moisture contents (wet or dry). Covering with either a double layer of Dewitt N-Sulate™ insulation fabric or a double layer of Dewitt N-Sulate™ insulation fabric and a single sheet of 4 mil white polyethylene plastic on top of the insulation fabric, wet substrate treatments, low fertility rates and combinations of both, improved survival and vigor for all three tested Pennisetum species and cultivars. In the second experiment, rooted liners of P. alopecuroides, P. "Hameln" and P. "Little Bunny," were potted. Treatments included, two transplanting times (young or old), two fertilizer rates (low or high) and two substrate moisture contents (wet or dry) at the UHC and Poplar Ridge Nursery (Montross, VA) (PR). Vigor was improved for P. alopecuroides (at PR) and P. "Little Bunny" (at both locations) with the young transplanting time. In the third experiment, older plant material of P. alopecuroides, P. "Hameln" and P. "Little Bunny," were subjected to fertility treatments of no additional fertilizer or top-dressed at a low, medium or high rate . A high fertility rate reduced survival and vigor for P. "Little Bunny." In the fourth experiment rooted liners of Echinacea purpurea "Hot Papaya," Echinacea purpurea "Milkshake," Gaillardia x grandiflora "Gallo Peach," Heuchera x villosa "Pistache," Heuchera x villosa "Brownies," P. alopecuroides, P. "Cassian," P. "Hameln" and P. "Little Bunny," were potted and overwintered at the UHC or Poplar Ridge Nursery (Montross, VA) (PR) or Riverbend Nursery, Inc. (Riner, VA) (RB). Treatments included, utilizing two overwintering covers, two fertilizer rates (low or high) and two substrate moisture contents (wet or dry). Vigor at the UHC, was reduced with the high fertility rate for E. "Hot Papaya" and H. "Brownies." A double layer of Dewitt N-Sulate™ insulation fabric and white polyethylene plastic on top of the cover, in combination with the wet substrate moisture treatment improved vigor of E. "Hot Papaya."A double layer of Dewitt N-Sulate™ insulation fabric in combination with the wet substrate moisture content and the high fertility rate reduced P. "Cassian" vigor. No overwintering cover reduced P. "Hameln" vigor. No overwintering cover and the high fertility rate reduced P. "Little Bunny" vigor. Vigor at PR was improved with the high fertility rate for E. "Milkshake," G. "Gallo Peach" and H. "Brownies." At RB, a double layer of Dewitt N-Sulate™ insulation fabric in combination with the low fertility treatment and no cover in combination with the high fertility treatment reduced vigor for E. "Milkshake" and P. "Little Bunny," respectively. No cover in combination with the wet substrate moisture treatment reduced vigor for G."Gallo Peach."

A combination treatment (AFM), designed to decompact and amend urban soils, and its individual components (air tillage, fertilizer, and mulch) were tested to determine their effects on fine root morphology. The site was an urban area located in Anderson, SC and included 50 red maples (Acer rubrum) growing in compacted, nutrient poor soils. Treatments were installed in November 2005, and data was collected through summer 2008. Data collection included minirhizotron images, soil moisture readings, soil temperature readings, and pre-dawn leaf water potentials. The AFM treatment had the lowest root production, root standing crop, and median root lifespan. The AFM treatment had the highest rate of root turnover. Median root lifespan for the AFM treatment was 248 days, followed by the mulch-only treatment which had a median root lifespan of 434 days. Median root lifespan for all other treatments exceeded 800 days. The mulched plots (AFM and mulch-only) had significantly higher soil water content and foliar leaf water potentials during periods of summer drought. Overall, the AFM treatment produced and maintained the fewest number of roots, had the highest rate of root turnover, but provided the most improvements to previously measured soil parameters as well as overall tree appearance and performance.

The Tarahumara are one of the most isolated and intact indigenous groups in Mexico. Their agriculture has traditionally been practiced within the steep canyons and uplands of the Sierra Madre Occidental in southwestern Chihuahua. Adapting to these rugged conditions, the Tarahumara developed a variety of agricultural techniques that allowed them to be self-sufficient in food production and independent of external inputs. As varied and ingenious as their techniques are, they share one main objective -- to overcome the lack of organic matter in the stony mountain soils. Since the arrival of the Spaniards, the addition of organic matter has involved large amounts of animal manure to increase organic matter in the soil and maintain fertility. The focus of this study is to investigate new agricultural techniques that the Tarahumara are adopting due to the pressures of globalization and alleged climate change. These new technologies may still include many traditional agricultural methods, but they are increasingly using commercially available fertilizers and other modern agricultural additions, thereby losing self-sufficiency. This study includes in depth interviews with 28 Tarahumara farmers to better understand the modern agricultural techniques, their motivations, and overall sustainability. Soil samples determined the viability of Tarahumara agricultural techniques on soil fertility by examining the visual description, organic matter content, soil texture, and a chemical analysis. The analyses showed that traditional Tarahumara agricultural practices are efficient and sustainable, while modern additions are often ill-suited for their environment and are disruptive to Tarahumara culture.

Phosphorus (P) use in the turfgrass industry has recently become heavily scrutinized due to its suspected contribution to eutrophication of lakes and streams. Inorganic P is a highly immobile nutrient in the soil, binding tightly to organic matter, soil particles, and minerals immediately following fertilizer application. Though many studies have shown that P run-off from turf is not a major source of water pollution, and in many ways helps prevent it in urban and other settings, restrictions are being placed on fertilization of turf with products that contain P. The portion of P in the soil that is available for plant use, inorganic P, is only a small fraction of the total P that exists at any time in the soil. Phosphorus transformations between the unavailable organic P form and inorganic P in soil is not completely understood given that the process depends on a combination of many factors such as soil moisture; pH; temperature or seasonality; spacial variability; presence or absence of other nutrients such as nitrogen (N), iron (Fe), aluminum (Al), carbon (C) and calcium (Ca); soil type; microbial activity; climate; vegetation; etc. A field study was conducted in 2006-2007 at the Ohio Turfgrass Research and Educational Facility, Columbus, Ohio to observe the effects of two of these factors, temperature or seasonality and the presence of nitrogen, on soil P availability. While applications of nitrogen alone in the past have been shown to maintain or increase available P levels in the soil, little evidence was seen here. Regardless of fertilizer treatment or timing, plant available P levels in all plots continuously decreased throughout the study indicating no treatment by time interaction. Some fertilizer treatment effects were observed that indicate that nitrogen fertilizer source can produce changes in plant available phosphorus.

Greenhouse grown tomato fruits and tissues were tested for the presence of Salmonella after the plants had been treated with Salmonella contaminated irrigation water or grown from contaminated seeds. Greenhouse grown tomato plants were placed into eight different groups. Groups one through six consisted of five plants each and were treated with 350 ml of 10^6 Salmonella contaminated irrigation water over a course of 70 days; group one received one 350 ml 10^7 Salmonella treatment, group two received two treatments, and so on, the treatments were scheduled every 14 days. Group seven was the control that consisted of five plants and received no Salmonella treatment. Group eight was grown from seeds that had been contaminated with Salmonella by soaking the seeds in a 10^8 Salmonella suspension for 24 hours at room temperature, and received no Salmonella watering treatment. A total of 128 tomatoes were sampled from the tomato plants of all three groups and none tested positive for Salmonella. Tissue samples consisting of roots, leaves, and stems, and were collected from one plant per each of three replications. No leaves or stems contained Salmonella, however, five of the twenty-four root samples were positive for Salmonella. In a second study, Salmonella was tested for its ability to survive in three concentrated fertilizer stock solutions and 1.6% diluted solutions of the fertilizer. Fertilizer sample CF-S was a stock solution of commercial 20N-4.4P-16.6K fertilizer, US-S was a mix of 11.3 kg UltraSol, 4.5 kg Epsom Salts, and 2.3 kg 0N-0P-43.2K in 114 L water, Fertilizer CN-S is a mix of 11.3 kg Calcium Nitrate and 56.7 g Iron chelate (10%) to 30 L water; Fertilizers CF-1.6, US-1.6, and CN-1.6 were the 1.6% fertilizer dilutions respectively. There was no significant difference (p

Hardwood stands in the southern U.S. are often regenerated naturally following clearcutting, with little or no silvicultural intervention in the early stages of stand development. Fertilizer was applied to a very young naturally regenerating stand in order to evaluate the effectiveness of nutrient addition as a silvicultural tool in recently clearcut stands and to better understand the ecological relationships between site fertility and stand development. The study was installed on a rising 2-year-old naturally regenerated mixed pine-hardwood stand in the Hill Research Forest in the Piedmont region (Durham County) of North Carolina. Dominant species were red maple (Acer rubrum), sweetgum (Liquidambar styraciflua), white oak group (Quercus alba, Quercus phellos and Quercus prinus), redbud (Cercis canadensis), hickory (Carya ovata), red oak group (Quercus falcate, Quercus rubra and Quercus coccinea), loblolly pine (Pinus Taeda) and tulip poplar (Liriodendron tulipifer). Fertilizer treatments were broadcast applied and consisted of an untreated control (Control), nitrogen (N) treatments, nitrogen and phosphorus (N+P) treatments, and nitrogen, phosphorus and potassium (N+P+K) treatments (respectively at 200 kg N per ha, 50 kg P per ha and 100 kg K per ha). Tree heights were recorded in June 2004 before treatment effects and for height and ground line diameter in October 2005. Stem origin and foliar nutrient concentrations (for red oak, loblolly pine and tulip poplar) were determined. Data was analyzed for treatment differences in ground line diameter, height, mean tree volume, groundline basal area, volume per hectare, density, and species composition on a whole stand basis as well as for the largest 16 trees per plot regardless of species, dominant species, and the 10 largest trees per species per plot for hickory, loblolly pine, red maple, red oak group, sweetgum, tulip poplar and white oak group. On a whole stand basis, increased growth rates were observed for N+P and N+P+K plots. Fertilizer treatments did not affect total stand density, but the density of evergreens significantly decreased in N+P plots. The density of stems of stump origin also increased in plots receiving N+P. Density of sweetgum significantly increased and hickory density decreased with the application of N+P. Dominant hardwood species (with the exception of tulip poplar) responded with an increase in height to N+P fertilizer treatments. Tulip poplar increased in groundline diameter, height and mean tree volume with the application of N+P. Loblolly pine responded to N+P+K fertilizer treatment with an increase in height, diameter and volume over the Control. The 16 largest trees responded with increases in GLD with N+P and N+P+K treatments and with increases in height with N, N+P and N+P+K treatments There was no growth response among treatments for the 10 largest trees per species per plot, with the exception of red oak which responded with an increase in height in N+P plots. There were slight differences among treatments in elemental foliar nutrients in larger red oak, loblolly pine and tulip poplar trees, but none were found to be deficient. The lack of growth response to N alone suggests the primary nutrient limitations for the site is not N or al least N alone. However, the strong response to N+P in hardwoods and N+P+K in loblolly pine suggests the site is deficient in these elemental combinations. Current and projected growth responses, both on a whole stand level and among individual species, indicate that the use of N+P fertilizer may be an effective silvicultural instrument to increase growth and accelerate stand development in very young naturally regenerated stands, and thereby shorten rotation time.

This research proposes a system that uses the waste generated by coffee processing to generate biogas and fertilizer, called AD-Coffee Waste System (AD-CWS). The biogas will be used to dry coffee beans and the fertilizer will be sold. Through this study it was proven that AD-CWS is feasibility. AD-CWS will not only eliminate coffee processing waste discharge into waterways, but it will also generate revenue through fertilizer and methane sales. At this time, further studies are needed to verify the biogas yield from coffee pulp at thermophilic temperatures (above 55°C) in order to properly forecast revenues. Enforcement of environmental laws in Mexico will result in fines to the coffee industry for discharging coffee waste into waterways, increasing coffee processing operating costs. AD-CWS can help the coffee industry comply with environmen¬tal regulations and avoid fines.