Master of Science / Department of Agronomy / Gary M. Pierzynski / Soil chemical and physical properties beneath cattle feedlot pens are largely unstudied. This project was conducted to survey select soil chemical and physical properties of soil beneath active open air cattle feedlots. At four cattle feedlots in Kansas, the concentrations of NH4-N, organic-N, organic-C, Cl-, and P were high at the surface and rapidly decreased within 1.00 m. At three of the four feedlots, NO3-N was generally below background concentration (4.1 mg kg-1) while one feedlot had a >75 mg kg-1 increase in the top 1.00 m. Based on feeding data, only a small percent (7.9 to 1.2) of the total N deposited on the surface was found in the top 1.00 m below the pen surface for a range of 25 to 60 years of operation. While in use, these feedlots do not appear to have a high potential for groundwater pollution from NO3-N leaching. However, if they were to become inactive they may pose a severe threat to groundwater quality from organic-N mineralization and NH4-N nitrification. If feedlots were closed and the land could be largely remediated by removing a layer of soil, these feedlots would have an average 48% profile N removed in a 0.25 m thick layer. A chamber, a modified vacuum desiccator, was tested for the investigation of NH3 volatilization from soil in the laboratory. Ammonia volatilization at the soil surface is dependent on air flow, soil and air temperatures, soil water content, pH, the concentrations of NH3 and NH4+ in the air and soil solution, and factors affecting soil temperature including humidity. This chamber was built to control and/or quantify as many of these variables as possible. A technique for quantifying and predicting NH3 volatilization is important because AFOs are one of the largest contributors of NH3 to the atmosphere, which can cause acid precipitation and particulate matter deposition downwind from the operation. The chambers created allowed for repeated measurements with little error and appear to be a feasible, inexpensive apparatus to investigate NH3 volatilization mechanisms. Using synthetic urine as an N source, NH3 volatilization was affected by initial soil moisture content and soil texture and may be affected by initial soil pH. This chamber has promise to provide excellent data to assist the efforts being made to understand and model NH3 volatilization from feedlot pens.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Kimberly A. Williams / The use of calcined clays contributes properties of nutrient and water retention to soilless root media, which varies greatly depending on the parent clay and calcining treatment. This research characterized phosphate (PO[subscript]4) sorption of various calcined clay products, including low volatile and regular volatile material (LVM and RVM) 2:1 Attasorb clays (Engelhard Corp.), 2:1 Terra Green LVM clays (Oil-Dri Co.), and Turface (Profile Products LLC) at various particle sizes; 1:1 kaolin clays (Thiele Kaolin Co.) in powder form, and diatomaceous earth (Diatomite, Eagle Picher Minerals, Inc.). Three of the calcined materials, Terra Green montmorillonite and Attasorb attapulgite (which had high PO[subscript]4-sorption based on isotherms), and diatomaceous earth (which had negligible PO[subscript]4-sorption) were evaluated as components of soilless root media in two separate greenhouse experiments. The effect of the calcined materials, rate of incorporation (0%, 5%, 10% and 20% by volume in a mix with peat and perlite), and PO[subscript]4-P application rate (0, 5, 15, 45 mg.L[superscript]-1 PO[subscript]4-P) on plant growth, effluent P content and water use were determined during production and post-production of Impatiens wallerana Hook f. 'Tempo Rose'. The calcined materials varied in their ability to adsorb PO[subscript]4-P and generally yielded L-type isotherms. Laboratory results indicated potential for substantive P retention by several of the calcined materials when used in container production. For most materials, PO[subscript]4-P sorption did not show pronounced pH dependence. During production and post-production, the test materials not only improved PO[subscript]4-P retention but also water retention and water use efficiency while still maintaining optimal physical properties at incorporation rates of 5 to 10%. Diatomaceous earth resulted in PO[subscript]4-P retention not significantly different from the calcined clays.

Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Rhonda R. Janke / Petiole sap nitrate-nitrogen (NO3-N) analysis with handheld meters is a valuable tool in applying in-season nitrogen (N) for many crops. Sufficiency levels have been determined for several leafy green crops, including lettuce (Lactuca sativa L.) and cabbage (Brassica oleracea L.), but not for pac choi (Brassica rapa L.). The response of pac choi to different fertilizer rates and sources [conventional and organic] has established optimal soluble N application rates and Cardy meter sufficiency ranges. Greenhouse experiments were conducted during summer and fall of 2008 in Manhattan, KS. Conventional soluble fertilizer was formulated from inorganic salts with a 4 NO3-N: 1 ammonium ratio. Phosphorus was held at 1.72mM and K at 0.83mM for all treatment levels. The organic soluble fertilizer, fish hydrolyzate (2N:1.72P:0.83K), was diluted to provide the same N levels as with conventional treatments. Both fertilizers were applied at rates of 0, 32, 75, 150, 225, 300, and 450 mg. L-1. Seedlings were transplanted and fertilizer application began at 18 days. Plants were harvested at seven weeks (five weeks post transplanting) after receiving 15 fertilizer applications during production. Samples of the most recently matured leaves were harvested weekly and analyzed for petiole sap NO3-N and leaf blade total N concentration. Leaf count, leaf length, and chlorophyll content were also measured weekly. Fresh and dry weights were determined on whole shoots and roots. Optimum yield was achieved at the 150 mg. L-1 fertility rate with both conventional and organic fertilizers. Field and high tunnel experiments were conducted during fall 2008 to validate the sufficiency ranges obtained from the greenhouse studies. Based on field and high tunnel results, sufficiency levels of NO3-N for pac choi petiole sap during weeks 2 to 3 of production were 800-1500 mg. L-1, and then dropped to 600-1000 mg. L-1 during weeks 4 through harvest for both conventional and organic fertilizers sources. These ranges could vary based on the variety of the crop, the fertility of soil, and certain environmental factors such as photoperiod, light intensity. However, we found that petiole sap nitrate always increased to the point associated with the maximum biomass, followed by a plateau where sap nitrate remained constant. This characteristic of the Cardy meter can provide the growers with a practical methodology to generate their standard curves under specific conditions to guide in-season N applications. Total N in leaf tissue showed fewer fertilizer rate effects than petiole sap NO3-N. Chlorophyll content was not useful in evaluating pac choi N status.

Reducing the rates of greenhouse gas (GHG) emissions is critical in combatting global climate change. Carbon dioxide (CO2) and methane (CH4) are the two most important carbon-based GHGs, for their atmospheric warming potential. Wetlands such as the Florida Everglades play major roles in the global carbon cycle, as varying hydrologic conditions lead to differential production rates of these two GHGs. This study measured CO2 and CH4 emissions in a re-created Everglades ridge-and-slough wetland, where water levels were controlled to reflect natural flood patterns. As expected, lower elevations were flooded longer and produced more CH4, while higher elevations produced more CO2. Since CH4 has a relatively high global warming potential, CO2 production would need to be 70 times that of CH4, to balance their GHG output. The average ratio of CO2 to CH4 across elevations was 22.0 (mol:mol), indicating that future water management within wetlands should consider GHG production potential.

Invasive plant species are major threats to the biodiversity and ecosystem stability. The purpose of this study is to understand the impacts of invasive plants on soil nutrient cycling and ecological functions. Soil samples were collected from rhizosphere and non-rhizosphere of both native and exotic plants from three genera, Lantana, Ficus and Schinus, at Tree Tops Park in South Florida, USA. Experimental results showed that the cultivable bacterial population in the soil under Brazilian pepper (invasive Schinus) was approximately ten times greater than all other plants. Also, Brazilian pepper lived under conditions of significantly lower available phosphorus but higher phosphatase activities than other sampled sites. Moreover, the respiration rates and soil macronutrients in rhizosphere soils of exotic plants were significantly higher than those of the natives (Phosphorus, p=0.034; Total Nitrogen, p=0.0067; Total Carbon, p=0.0243). Overall, the soil biogeochemical status under invasive plants was different from those of the natives.

In a large agricultural operation, such as the one at Cal Poly San Luis Obispo, disposal of deceased animals is an immense issue. The cost of transporting and rendering every dead animal is inhibitory to the general function of the agricultural operations and their thin budget. Therefore, we propose that composting mortalities could be an economical alternative. Composting is a recognized method for taking animal waste products along with carbon waste and turning it into a pathogen-free, nutrient-rich topsoil. Carcass composting is in fact performed in other countries and states to varying degrees of success. However, the California EPA limits carcass composing to only private land. Therefore, the purpose of this work was to determine the efficacy of killing pathogens by composting using bench top composting models. Ultimately, our goal is to provide “proof of concept” data in order to gain permission for a full-scale carcass compost pile to be set up at Cal Poly San Luis Obispo. Using thermo tolerant Salmonella senftenberg as an indicator organism, we performed bench top trials of traditional and carcass compost in the lab. Samples were inoculated with S. senftenberg and kept at 55°C for 15 days in accordance with the California EPA and Test Method for the Examination of Composting and Compost (TMECC). Samples were then plated and processed for multiple tube analysis and most probable number. Samples were also partitioned for a viability qPCR with propidium monoazide (PMA) to compare to the classic techniques. Using these methods we were then able to track and produce thermal death time data for S. senftenberg in both traditional and carcass compost. By comparing the types of compost, we were able to determine that the composting method presented by the California EPA and the TMECC produces safe, pathogen free compost, even when inoculated carcasses were introduced. However, even with removal of dead cells by PMA, qPCR did not outperform the classical microbiological methods for as tracking pathogen killing.

In Peru, nearly 32 million people rely heavily on human-made coastal irrigation agricultural hubs that rely on water from melting glaciers, snowpack, and rain transported by rivers and canals from high in the Andes. However, Peru’s water resources are in a vulnerable state as climate change has shifted rainfall patterns causing glacier retreat affecting nearly the loss of one-third of the glaciers. In recent decades, an increase and expansion of irrigation projects in Peru require agriculture practices to consider environmental impacts directly. Now is the time to explore the sustainability of the desert agroecosystems and understand how different water management practices influence the supporting soil’s health so decision-makers can plan for future change in water resources and any feedbacks to the productivity of the soils. Over the past 40 years, Peru has led some of the largest scale water management projects on earth to convert infertile coastal desert soils into irrigated agricultural land. Still, these efforts can come at a severe local cost with impacts to groundwater quality, salination of the soil, toxic concentrations of trace metals due to evaporation, and overuse of fertilizer and pesticides. This thesis presents a study to assess how drip irrigation impacts desert soil chemistry within one of Peru’s desert irrigation projects in Arequipa’s southern district. We explored a chronosequence of drip irrigation in vineyards of 9-, 16- and 35- years. Results showed that both soil carbon and salinity accumulated progressively over time but that spatial accumulation patterns were influenced by proximity to the irrigation drip line. By 35 years, salinity levels exceeded what would be tolerances for most crops. Trace metals, such as Mn, Zn, and Ni, increased with time under drip irrigation and have significant relationships with Fe, present in the highest concentrations, seemingly controlling the patterns due to co-precipitation. However, no trace metals were found in quantities that would exceed Peru’s limits for agricultural soils. While drip irrigation is considered a water conservation strategy and widely promoted in the region over other irrigation techniques like high water volume furrow irrigation, its use may accelerate localized negative impacts to surface soil health. These progressive changes highlight the need for effective monitoring and salinity mitigation strategies in the region. This project is part of the bilateral technical program between Purdue University and Universidad Nacional San Agustín (UNSA) called the Arequipa Nexus Institute for Food, Water, Energy, and the Environment.

<div>In fire-prone forests, tree taxa and burn temperature are the major controllers of the chemical and physical properties of pyrogenic organic matter (PyOM), the aromatic carbon-rich product of the incomplete combustion of plant biomass, that accumulates in soil in such settings. These controls also dictate how soil microbes can degrade plant C once it enters into soil as previous studies demonstrate that increased fire temperature results in low PyOM degradability but also impacts the decomposition of the original soil. However, we know little about how taxa and temperature of C-inputs impact the production and accumulation of cellular residues from soil microbes, which can be the dominant source of stabilized soil organic matter in many ecosystems. </div><div>This work presents the results of the analysis of soil microbial amino sugars, as proxies for soil microbial necromass, from long-term soil incubation experiments, 180 and 600 days, that were amended with jack pine (JP) and red maple (RM) wood or their PyOM produced at 300°C or 450°C. Both wood taxa amendments resulted in an increase in microbial sugar residues compared to non-amended soils but RM, the taxa with the highest proportion of soluble sugars and low tannin content, exhibited the highest percentage increase. Soils amended with PyOM exhibited lower amino sugar content as compared to their wood but no difference compared to controls (non-amended soils). There was no difference in soil amino sugars observed between the PyOM derived from the two taxa nor between the temperature of pyrolysis, possibly due to only small amounts of bioavailable C and N in the PyOM. Total amino sugar concentrations varied significantly between PyOM and fresh wood treatments, with PyOM treatments yielding 659 – 730 μg/ g soil while wood treatments yielded 757 – 930 μg/ g soil early in incubations. While fungal-derived amino sugars were dominated in all treatments, longer soil incubation time, 600 days vs 180 days, resulted in a proportionately greater decrease bacterial-derived amino sugars. Overall, at 180 days, PyOM treatments exhibited 19-27% of soil N and 4-5% of soil C quantifiable as amino sugars while wood treatments exhibited 27-28% of total soil N and 6-7% of total soil C as amino sugars. This work shows, for the first time, that on a per C or per N basis, PyOM versus fresh wood addition to soils will result in a net depletion of microbial residues. The variable response in amino sugars between treatments and incubation time highlights the importance and dynamic nature of the physicochemical characteristics of organic matter input to soil in controlling the contribution of soil microbial residues to that soil. </div><div><br></div>

No description available.

The United Nations organization for food and agriculture argues that humanity hastaken the soils of the world for granted. Due to chemical pollution, erosion,salinization, compaction, and acidification, 33 percent of the soils are moderately orhighly degraded. If humanity loses more productive soils, there is a risk that foodinsecurity and poverty would increase as well as the diminishing of severalecosystem services.This study focuses on the anthropogenic external factors that affect the agriculturalfields since the conventional and organic farmers use different methods relating tofertilizers, manure, and pesticides. A comparison of soil organic matter between soilsamples from organic and conventional farms in Sweden was carried out, throughsoil sampling and then analyzed with the combustion method. The study alsoevaluates the effect of erosion on the fields in the sampling region.According to this study’s results, there is no significant difference between theamount of soil organic matter in conventional or organic farming soil in southeastSweden, and there has been no erosion on the fields in the past seven years since theSOM content had neither increased nor decreased. This knowledge can be of furtheruse in soil science studies.