Plant Science & Landscape Architecture Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2797
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Item Utilization of Gypsum as a Filter Material in Agricultural Drainage Ditches: Impacts of Land Application on Soil Fertililty Conditions(2010) Grubb, Karen Lyn; McGrath, Joshua M.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nutrient loads in drainage ditches is to install filter structures containing P sorbing materials (PSMs) including gypsum to remove P from ditch flow. One projected advantage would be the potential application of spent PSMs to agricultural fields to provide nutrients for crop production after the filter has lost its effectiveness. The study evaluated the feasibility of this strategy. Gypsum was saturated at two levels on mass basis of P, and applied to two soil types, a silt loam and a sandy loam and applied at both a high and low rate. The treated soils were incubated at 25° C, and samples were collected at 0, 1, 7, 28, 63, 91, 119, and 183 days after saturation.Item Redoximorphic Features Induced by Organic Amendments and Simulated Wetland Hydrology(2010) Gray, Adam Lincoln; Rabenhorst, Martin C; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)During wetland construction, it is common to add organic amendments to the soil, although little research has evaluated the effects of organic additions on the development of redoximorphic features. The objective of this study was to evaluate the effects of adding different types of organic materials, using different methods of incorporation, on the formation of redoximorphic features under hydric soil conditions. Five types of organic materials were incorporated into soil cores lacking redoximorphic features, using three incorporation methods. Cores were established as mesocosms in a controlled greenhouse environment or transplanted into a natural wetland. Mesocosms were periodically dissected and examined for newly formed redoximorphic features. The method of incorporating organic materials had a significant influence on the development of redoximorphic features, but the type of organic material had no significant effect. Organic materials should be concentrated into deeper zones during wetland construction to maximize development of redoximorphic features.Item CALIBRATING CAPACITANCE SENSORS TO ESTIMATE WATER CONTENT, MATRIC POTENTIAL, AND ELECTRICAL CONDUCTIVITY IN SOILLESS SUBSTRATES(2009) Arguedas Rodriguez, Felix Ruben; Lea-Cox, John D; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The nursery and greenhouse industry requires precise methods to schedule irrigations, since current practices are subjective and contribute to water and nutrient runoff. Capacitance sensors were calibrated to precisely estimate substrate water content, matric potential, and pore water electrical conductivity (EC) in five soilless substrates. Regression coefficients (R2) ranged from 0.29 - 0.88 and 0.16 - 0.79 for water content in 5-cm and 20-cm column heights; matric potential R2 ranged from 0.10 - 0.98 and 0.79 - 0.98, respectively. Pore water EC calibrations were investigated, contrasting two sensor types and two prediction models. Results were applied to an empirical greenhouse dataset. Better precision and accuracy were achieved with ECH2O-TE sensor and Rhoades model. Capacitance sensors provide precise estimates of plant-available water in most soilless substrates, while pore water EC accuracy and precision depends on the sensor-model combination. These results will enable growers to precisely schedule irrigations based on water content and pore water EC.Item Alleviation of Soil Compaction by Brassica Cover Crops(2009) Chen, Guihua; Weil, Ray R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soil compaction is a worldwide problem in modern agriculture associated with overuse of heavy machinery and intensification of cropping systems. Though tillage is traditionally used to alleviate compaction effect, increasing concerns about environmental impacts of tillage have led to interest in conservational tillage systems and incorporation of cover crops into crop rotations. Previous study showed soybean (Glycine Max L.) roots grew through a plowpan soil using channels left by canola (Brassica napus) cover crop roots, a process termed "biodrilling" to alleviate compaction effect. However, this study did not provide any quantitative data to support the observational conclusion. We studied "biodrilling" abilities of three cover crops and the effects of "biodrilling" on corn (Zea mays)/soybean growth by conducting three experiments. The first two experiments included three surface horizon compaction treatments (high, medium and no compaction), four cover crops [FR (forage radish: Raphanus sativus var. longipinnatus, cultivar `Daikon') and rape (rapeseed: Brassica napus, cultivar `Essex') (tap-rooted species in the Brassica family), rye (cereal rye: Secale cereale L., cultivar `Wheeler') (fibrous-rooted species) and NC (no cover crop)] in Exp. 1, and three cover crops (FR, rape and NC) in Exp. 2. The third experiment was conducted on field with a legacy plowpan (subsoil compaction) using FR, rye and NC cover crops. Roots of FR were least inhibited by compaction, while rye roots were severely arrested by compaction. The order of "biodrilling" ability was FR > rape > rye. Soil bulk density, strength and least limiting water range were controlled by compaction treatments. Soil air permeability was greatly reduced by compaction. Air permeability was greater in rape/FR treatments than in rye/NC treatments under high/medium compaction. Corn/soybean root penetrations, subsoil water uptake in the compacted soils were enhanced by FR/rape treatments but not by rye/NC treatments. Compaction decreased corn yield only in Exp. 2 where soil sand fraction was greater. The yield of corn was greater in three cover crop treatments than in NC control. In terms of "biodrilling", Brassica cover crops (FR and rape) were more effective than rye cover crop, would alleviate effects of soil compaction on plant growth in no-till farming systems.Item Forage Radish Cover Crop Effects on Mycorrhizal Colonization and Soil Test Phosphorus(2009) White, Charles Macaulay; Weil, Ray R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Forage radish (Raphanus sativus L. var. longipinnatus) and cereal rye (Secale cereale L.) cover crops were examined for their effects on arbuscular mycorrhizal colonization and P acquisition of a subsequent corn (Zea mays L.) silage crop. Soil test P following these cover crops was also measured in bulk soil collected at three depths in the surface soil and in soil sampled within 3 cm of forage radish tap root holes. Forage radish never decreased mycorrhizal colonization and rye sometimes increased colonization of the subsequent crop compared to growing no cover crop. The extent of colonization of corn roots by arbuscular mycorrhizal fungi was positively correlated with corn shoot tissue P concentrations. Slight vertical soil test P stratification in the bulk soil occurred following both forage radish and rye cover crops at some sites. A large increase in soil test P occurred within 3 cm of forage radish tap root holes.Item HYDROMORPHOLOGY OF ANOMALOUS BRIGHT LOAMY SOILS ON THE MID-ATLANTIC COASTAL PLAIN(2009) Zurheide, Philip Klaus; Rabenhorst, Martin C; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Some loamy textured soils along the Mid-Atlantic coastal plain undergo extended periods of saturation or ponding, yet lack the hydromorphology that identifies them as hydric by any of the currently approved Field Indicators of Hydric Soils (FI). Termed Anomalous Bright Loamy Soils (ABLS), these were identified at four research sites on the Delmarva Peninsula. The hydrologic and biogeochemical status of these soils was monitored for three years along a hydrosequence at each site. A series of field and lab experiments were run to investigate the possible causes for the ABLS-phenomenon. The most likely cause is a combination of low hydrologic gradient coupled with the length of time since saturation. Using observed morphology, a newly developed Field Indicator successfully discriminated between five hydric soils that lacked an approved indicator and those that were not hydric. This indicator has now been approved as an official FI of Hydric Soils (F20).Item Multi-Scale Pedologic Investigation of Manganiferous Soils in the Maryland Piedmont(2008) Bourgault, Rebecca; Rabenhorst, Martin; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Manganese oxides are usually found in trace quantities in soils, but they are important due to their effects on soil chemistry and morphology. There are rare soils in the Maryland Piedmont that have extremely high amounts of manganese oxides that have not been previously studied. These manganiferous soils were examined at multiple scales in order to determine their spatial extent, to characterize their fundamental morphology, mineralogy, and chemical and physical properties, and to better understand their pedogenesis. The soils occupy areas of 1-2 ha in size, within 200 km2 in eastern Frederick County and western Carroll County. The soils can have as much as 140 g kg-1 Mn as oxides, which pigments the entire soil matrix black in subsoil horizons. It appears that the black, porous, Mn-rich material is derived directly from the dissolution of marble bedrock and accumulation of silicate residues plus Mn and Fe from within the rock.Item Oxidation-Reduction Transformations of Chromium in Aerobic Soils and the Role of Electron-Shuttling Quinones in Chemical and Microbiological Pathways(2008-05-05) Brose, Dominic; James, Bruce R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soils from three toposequences in Maryland with minimal heavy metal contamination were sampled to investigate oxidation-reduction transformations of chromium in whole soil samples. Chromium (VI) reduction to Cr(III) was observed in all 18 samples, and 11 demonstrated enhanced reduction with the electron shuttle anthraquinone-2,6-disulfonate (AQDS). Oxidation of Cr(III) to Cr(VI) was observed in 12 samples, and 7 samples demonstrated diminished oxidation with AQDS. Lactate was added to the Watchung series to enhance biological activity, and high salt concentration was added to inhibit it. Both treatments reduced Cr(VI) to below detection limits by 11 d, suggesting abiotic reduction. The control treatment demonstrated reduction of Cr(VI) without soil. To further investigate, increasing lactate concentrations were added to Cr(VI) and AQDS. Reduction increased with increasing concentration; 60 mM lactate reduced all Cr(VI) within 1 hr. Other organic acids were tested for similar interactions; tartrate and citrate reduced Cr(VI), which was enhanced with AQDS.Item Pedogenesis, Inventory, and Utilization of Subaqueous Soils in Chincoteague Bay, Maryland(2007-11-28) Balduff, Danielle Marie; Rabenhorst, Martin C.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Chincoteague Bay is the largest (19,000 ha) of Maryland's inland coastal bays bounded by Assateague Island to the east and the Maryland mainland to the west. It is connected to the Atlantic Ocean by the Ocean City inlet to the north and the Chincoteague inlet to the south. Water depth ranges mostly from 1.0 to 2.5 meters mean sea level (MSL). The objectives of this study were to identify the subaqueous landforms, evaluate the suitability of existing subaqueous soil-landscape models, develop a soils map, and demonstrate the usefulness of subaqueous soils information. Bathymetric data collected by the Maryland Geological Survey in 2003 were used to generate a digital elevation model (DEM) of Chincoteague Bay. The DEM was used, in conjunction with false color infrared photography to identify subaqueous landforms based on water depth, slope, landscape shape, depositional environment, and geographical setting (proximity to other landforms). The eight such landforms identified were barrier cove, lagoon bottom, mainland cove, paleo-flood tidal delta, shoal, storm-surge washover fan flat, storm-surge washover fan slope, and submerged headland. Previously established soil-landscape models were evaluated and utilized to create a soils map of the area. Soil profile descriptions were collected at 163 locations throughout Chincoteague Bay. Pedons representative of major landforms were characterized for a variety of chemical, physical and mineralogical properties. Initially classification using Soil Taxonomy (Soil Survey Staff, 2006) identified the major soils as Typic Sulfaquents, Haplic Sulfaquents, Sulfic Hydraquents, and Thapto-Histic Sulfaquents. Using a proposed modification to Soil Taxonomy designed to better accommodate subaqueous soils with the new suborder of Wassents, soils of Chincoteague Bay were primarily classified as Fluvic Sulfiwassents, Haplic Sulfiwassents, Thapto-Histic Sulfiwassents, Sulfic Hydrowassents, and Sulfic Psammowassents. To illustrate the application of subaqueous soils information, the suitability of soils for submerged aquatic vegetation (SAV) habitat was assessed, based upon past and current growth patterns in Chincoteague Bay and sediment properties known to affect SAV establishment and growth. The refined soil-landscape models and extensive soil characterization obtained in this study have advanced our understanding of subaqueous soils in coastal lagoon systems, and should prove valuable to coastal specialists managing these critical resources.Item Winter annual rye cover crops in no-till grain crop rotations: impacts on soil physical properties and organic matter(2007-07-31) Bilek, Meredith; Coale, Frank J; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Winter annual cover cropping (WCC) is a common management practice subsidized by Maryland to protect water and soil quality. The affect of long-term incorporation of WCC on soil physical properties (SPP) is not well established. We hypothesized by increasing organic inputs WCC would improve SPP. To evaluate the effect of WCC and wheel traffic (WT) on SPP, we studied two long term rotations (corn/rye and corn/fallow) at two locations on the Coastal Plain (CP) and one on the Piedmont. WCC improved SPP, but only during the winter at the CP. High levels of WT compacted soil in both rotations. WCC and wheel traffic had no effect on SPP or organic matter at the Piedmont. We conclude, only during the winter did WCC improve SPP; however, due to the drastic annual changes, we hypothesize this improvement is due to soil disturbance caused by the grain drill planting the rye.
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