Landslides in the Southern Appalachian Mountains of East Tennessee often activate and reactivate. Often triggered by high-intensity or prolonged rainfall, landslides are responsible for infrastructure damage, closure of transportation routes, and even fatality. The study area is defined by the New River Watershed which has high elevation and steep slopes cutting through State Route 116. The route has hairpin turns and has experienced damage from past landslide events. The geology here is mostly shale and sandstones with coal bedding throughout. Much of the soil consists of a fine-loamy texture. Most drainage occurs from the New River, fed by runoff from slopes into roadways. This area experiences heavy rainfall with a yearly average of 70 inches. Landcover consists of a mostly forested landscape with shrubs and grassland. In response to previous landslides, the Tennessee Department of Transportation (TDOT) recently repaired six areas within the route intercepted by recent landslides. Aside from the landslides near TDOT’s corridors, approximately 50 additional landslides have been found using Google Earth and LiDAR data. Landslide hotspots were identified using kernel density estimation and the nearest neighbor index. A heuristic landslide susceptibility model was prepared by weighing the ArcGIS layers: slope, soil particle, geology, curvature, elevation, distance from the stream, and land cover, in their contribution to the previous landslides. Results indicate that additional sites in Anderson and Morgan County should be studied further for potential landslide-related damage. The study will improve the proactive decisions of TDOT and justify timely monitoring, maintenance, and strategic protection of the route from slope hazards.

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Master of Science / Department of Agronomy / Nathan O. Nelson / Phosphorus (P) is an essential nutrient in crop production, but P inputs to surface waters have resulted in impairments such as eutrophication and algae blooms. Non-point sources such as agricultural fields are a main contributor of P. Kansas, being a high agricultural dependent state, has frequent fresh water body impairments. Multiple erosion and transport processes contribute to P loss. While P loss from sheet and rill erosion has been studied extensively, P loss from ephemeral gully erosion is largely unknown. The objective of this study is to understand the effects ephemeral gullies have on the transport and transformation of P. Three fields in McPherson County with well-defined ephemeral gullies were studied. Soil samples were taken in field locations that are effected by ephemeral gullies at the 0 to 2, 2 to 5, 5 to 15, and 15 to 30 cm depths. Samples were analyzed for total P, anion exchange phosphorus (AEP) (labile P), ammonium-oxalate extractable Fe, Al, and P (Fe[subscript]ox, Al[subscript]ox, P[subscript]ox), Mehlich 3 extractable Fe, Al, Ca, and P (Fe[subscript]M3, Al[subscript]M3, Ca[subscript]M3, P[subscript]M3), equilibrium phosphorus concentration at zero net sorption (EPC[subscript]0), 1:1 soil to water pH, and texture. Soil testing showed that P quantities tend to be much higher in surface soils eroded by sheet and rill erosion and lower in subsoil soil that is eroded by ephemeral gullies. The quantity of sorptive elements such as Fe and Al, were not significantly different throughout the tested area except in areas of changing soil texture. EPC[subscript]0 testing showed it was likely that P desorbs from the surface erosion of sheet and rill and is adsorbing onto the subsoil eroded from ephemeral gullies. Sediment eroded by ephemeral gullies has a P buffering capacity greater than the sediment eroded by sheet and rill, and a small quantity of ephemeral gully subsoil will have a large effect on the dissolved P concentration of runoff. Sediment, total P loss and expected dissolved P in runoff was surveyed and modeled for two of the fields. Ephemeral gullies contributed to a majority of sediment and total P loss. The addition of ephemeral gully sediment to the erosional mix of sheet and rill sediment caused the dissolved P concentration to decrease from 0.0204 to 0.0034 mg L[superscript]-1 in one field and from 0.0136 to 0.0126 mg L[superscript]-1 in another. The results of this study show that best management practices (BMPs) such as grass waterways could cause the losses of total P to decrease as much as 2 to 12 times in fields with ephemeral gullies. However, reducing ephemeral gully erosion will likely increase dissolved P concentrations up to 600% more in runoff. Therefore, BMPs need to be combined to fully control P loss from agricultural fields.

The coralline soils of atolls suffer from multiple nutrient deficiencies that severely limit crop growth. This study was conducted to assess the nutrient status of the soils of the inhabited atolls within the Marshall Islands (MI), and to determine what local materials could be used to correct deficiencies limiting crop growth. Surface and subsoils from 25 atolls were collected and analyzed for their chemical properties, and soil test results were evaluated with a missing element pot study. Soil tests revealed that the MI soils were severely deficient in K (0.12 cmol c kg -1 ) and marginally deficient in Cu (0.13 ug g -1 ). The missing element study showed that the soil was deficient in K, S, N, P, and Cu. An incubation experiment and a series of greenhouse experiments were conducted to evaluate the ability of locally available organic materials to mineralize N and supply adequate nutrients to crops. Vigna marina and fish meal showed the highest N mineralization capacity, and the Gompertz equation provided the best fit. Chinese cabbage plants grew as well in soils amended with chicken manure, Vigna marina , and copra cake as they did in soil treated with chemical fertilizers. Plants grown in soil amended with fish meal did not grow as well due to inadequate K supply. Nitrogen recovery was highest in V. marina treatment at 92% followed by the chemical control (83%), chicken manure (34%), fish-meal (18%), and copra cake (9%). Added coconut leaves immobilized N and resulted in very poor cabbage growth. Comparisons between relative growth rate (RGR) and nutrient relative accumulation rate (RAR) showed that nutrients supplied from the V. marina amendment to the cabbage plant matched plant demand. In a rate experiment in the greenhouse, adding 10.1 g kg -1 of V. marina leaves (dry weight) supplied 350 mg N kg -1 to 5 week-old corn plants representing 38% of the total amount of N added in the amendment. Splitting the application quantity improved corn growth at the highest addition rate. Copra cake showed less promise as a suitable organic amendment. Supplementing copra with chemical N and P, and V. marina leaves with and without Cu and B did not improve crop growth compared with copra alone. The soil exhibited low P adsorption capacity, and corn and lettuce growth responded to high Olsen P soil levels. The results of the greenhouse experiments showed that V. marina is a potential organic fertilizer material to correct soil nutrient deficiencies for good crop growth in the Marshall Islands.

Manganese (Mn) in excess of crop requirements is a serious problem when manganiferous soils become acid, waterlogged or amended with organic materials. We investigated the dynamics of manganese phytotoxicity and tested management options for growing crops in acid soils with excess Mn. We hypothesized that Mn phytotoxicity is governed by water use and expressed as continuous negative interaction between current plant/leaf growth rate (RGR PLant/Leaf) and future Mn accumulation rate (RAR Mn); and that under growth conditions where RGRPlant/Leaf exceeds RAR Mn, excess Mn can be managed by maximizing RGR Plant/Leaf and minimizing RAR Mn. The parameters RGR Plant/Leaf and RAR Mn were calculated using the conventional growth analysis techniques. The dynamics of Mn phytotoxicity was investigated by growing Mn-tolerant Lee and Mn-sensitive Forrest soybeans in the greenhouse using Wahiawa series, a manganiferous Oxisol in Hawaii. The soybeans were grown at soil pHs 4.78, 5.5, and 6.00 and five growth conditions (control, 80-90% field capacity, 40% shading, green manure and phosphorus at 150 mg kg-1). RAR Mn consistently exceeded RGR Leaf in most treatments. Over the range of soil pH and growth conditions, we found strong positive correlation between RGR Leaf and RAR Mn, this correlation mediated by a more fundamental correlation of both rate processes to plant water use. The dynamics of Mn phytotoxicity, referred to as the 'dual feedback effect' model described a continuous negative interaction between current RGR Leaf and future RAR Mn and between current RAR Mn and future RGR Leaf. Manganese accumulation rate exceeded plant growth rate, leaf Mn increased with time and growth treatments did not affect growth rate unless soil pH was increased to eliminate excessive Mn in the soil. Field experiments were conducted in Rugao series, an acid Alfisol in Northern Philippines. The soil is acid (pH 4.40) with abundant Fe-Mn concretions within the surface 20-cm. Preliminary field experiment showed Mn phytotoxicity in local soybeans cv. PSB Sy2 and PSB Sy6 as leaf symptoms in addition to low plant growth rates and grain yields associated with leaf Mn exceeding a critical value of 500 mg kg-1. Results of a second field experiment showed that cultivar, liming, and the management of phosphorus (P), manure and mulching modified plant growth rate and enhanced tolerance to excess soil Mn. Lime control (2 t ha-1) neutralized half of the exchangeable AI while keeping saturated paste Mn in excess. Mulching did not affect saturated paste-and increased RAR Mn without affecting RGR Leaf. Increases in RGR Leaf due to P and manure were accompanied by increases in RAR Mn. This increase in RGR Leaf translated to increased yields even when RAR Mn and soil solution Mn were increased as in the case of manure addition. Increases in grain yield due to manure exceeded the increases due to lime or P. Chicken manure was more effective than green manure in increasing grain yield. Plant growth rate exceeded Mn accumulation rate, leaf Mn decreased with time and manure treatments alleviated Mn phytotoxicity despite an increase in soil Mn.

abstract: Mycorrhizal fungi form symbiotic relationships with plant roots, increasing nutrient and water availability to plants and improving soil stability. Mechanical disturbance of soil has been found to reduce mycorrhizal inoculum in soils, but findings have been inconsistent. To examine the impact of restoration practices on riparian mycorrhizal inoculum potential, soil samples were collected at the Tres Rios Ecosystem Restoration and Flood Control Project located at the confluence of the Salt, Gila, and Agua Fria rivers in central Arizona. The project involved the mechanical removal of invasive Tamarix spp.( tamarisk, salt cedar) and grading prior to revegetation. Soil samples were collected from three stages of restoration: pre-restoration, soil banks with chipped vegetation, and in areas that had been graded in preparation for revegetation. Bioassay plants were grown in the soil samples and roots analyzed for arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) infection percentages. Vegetations measurements were also taken for woody vegetation at the site. The mean number of AM and EM fungal propagules did not differ between the three treatment area, but inoculum levels did differ between AM and EM fungi with AM fungal propagules detected at moderate levels and EM fungi at very low levels. These differences may have been related to availability of host plants since AM fungi form associations with a variety of desert riparian forbs and grasses and EM fungi only form associations with Populus spp. and Salix spp. which were present at the site but at low density and canopy cover. Prior studies have also found that EM fungi may be more affected by tamarisk invasions than AM fungi. Our results were similar to other restoration projects for AM fungi suggesting that it may not be necessary to add AM fungi to soil prior to planting native vegetation because of the moderate presence of AM fungi even in soils dominated by tamarisk and exposed to soil disturbance during the restoration process. In contrast when planting trees that form EM associations, it may be beneficial to augment soil with EM fungi collected from riparian areas or to pre-inoculate plants prior to planting. / Dissertation/Thesis / M.S. Applied Biological Sciences 2012

abstract: Unmanned subsurface investigation technologies for the Moon are of special significance for future exploration when considering the renewed interest of the international community for this interplanetary destination. In precision agriculture, farmers demand quasi-real-time sensors and instruments with remote crop and soil detection properties to meet sustainability goals and achieve healthier and higher crop yields. Hence, there is the need for a robot that will be able to travel through the soil and conduct sampling or in-situ analysis of the subsurface materials on earth and in space. This thesis presents the design, fabrication, and characterization of a robot that can travel through the soil. The robot consists of a helical screw design coupled with a fin that acts as an anchor. The fin design is an integral part of the robot, allowing it to travel up and down the medium unaided. Experiments were performed to characterize different designs. It was concluded that the most energy-efficient speed from traveling down the medium is 20 rpm, while 60 rpm was the efficient speed for traveling up the medium. This research provides vital insight into developing subsurface robots enabling us to unearth the valuable knowledge that subsurface environment holds to help the agricultural, construction, and exploration communities. / Dissertation/Thesis / Video of Self Burrowing Robot travelling down the medium / Video of Self Burrowing Robot travelling out the medium / Masters Thesis Mechanical Engineering 2020