Pineview clay originates from a lacustrine deposit and has a clay content of approximately 55%. During the spring the soil is generally quite moist due to melting snow and rainfall, while ambient air temperatures are relatively cool. These factors cause soil warming on Pineview clay to be slow. Due to the slow soil warming process in the spring and due to the fine texture of this soil, it is important that the Pineview clay maintains a good soil structure. Little research has been carried out on Pineview clay as to the effect of tillage practices on soil structure. It was the purpose of this project to study changes in the properties of Pineview clay brought about by different tillage systems. In the first part of the project major adverse soil conditions that occur on Pineview clay were evaluated with respect to the emergence of barley. In the laboratory the effects of soil compaction and soil temperature were evaluated in terms of barley seedling emergence. The second part of the study consisted of determining the feasibility of several tillage systems and the use of a herbicide prior to tillage on Pineview clay. In the last part of the study four fall sod breaking tillage systems were evaluated in terms of their effect on soil physical properties, N transformations, crop growth and development, and economic returns. Barley seedling emergence in the laboratory was found to be affected by soil compaction and soil temperature. Between 5⁰ and 20⁰C the rate of barley emergence approximately doubled for every 5⁰C increment in soil temperature. Applying the herbicide Gramaxone prior to tillage improved soil break-up and control of sod regrowth, but the cost of this herbicide may be prohibitive. For sod breaking operations a stubble plow proved to be inadequate and a special sod breaking plow should be used. Rotovation prior to moldboard plowing improved soil break-up and control of sod re-growth. Chisel plowing resulted in a rough, mulched soil surface condition, which required many passes before a satisfactory level soil surface had been created. The four fall sod breaking systems were moldboard plowing (using a sod breaking plow) with and without prior rotovation, and chisel plowing with and without prior rotovation. The results indicate major differences due to the type of plow used (moldboard vs chisel) rather than the additional use of the rotovator prior to plowing. Moldboard plowing resulted in superior soil physical conditions, higher soil NO₃-N levels, higher crop yields and N uptake by the crop, and better economic returns than chisel plowing. The four tillage systems reached maximum profits under various fertilizer rates; $208.00/ha for moldboard plowing at 112 kg N/ha, $104.00/ha for rotovating and moldboard plowing at 56 kg N/ha, $71.00/ha for chisel plowing at 168 kg N/ha, and $39.00/ha for rotovating and chisel plowing at 0 kg N/ha. / Land and Food Systems, Faculty of / Graduate

This study was conducted to provide new and useful data about Pineview Reservoir and its watershed, produce water and phosphorus (P) budgets for Pineview Reservoir, test the validity of conclusions made in the Pineview Reservoir Total Maximum Daily Loading (TMDL) document, and create estimates of nitrogen (N) loading to the reservoir from both surface and ground water sources. The production of the water and P budgets, as well as the N loading estimates, was accomplished by measuring flow, nitrate, ammonium, total phosphorus (TP), and soluble reactive phosphorus (SRP) that was entering and exiting the reservoir through surface water sources and the reservoir outlet over a period of approximately 2 years (2008 to 2010). Estimates of ground water contributions to the reservoir were also made using ground water P and N concentration data from a parallel study and ground water flow estimates from the literature. In order to test the validity of claims made in the TMDL, internal reservoir parameters such as temperature, dissolved oxygen, TP, orthophosphorus (OP), nitrate, ammonium and dissolved iron (Fe) were measured at the surface, thermocline, and hypolimnion of five sampling locations within the reservoir over the same sampling period. Chlorophyll A was also measured near the surface of the sites during each sampling event. Contrary to the conclusions made by the TMDL it was found that the internal cycling of nutrients, especially P, is occurring in Pineview Reservoir and that annually observed phytoplankton blooms can be attributed to the release of benthic nutrients. It was also found that there is a large store of sediment P that is currently or potentially could be made available for transfer into the water column. It was estimated that 14,800 kg of P was exported from the reservoir over the one-year sample period of 4/15/2009 to 4/14/2010. This large P release is due to the practice of exporting P rich hypolimnetic water throughout the summer irrigation season. It was shown that more P could be exported if outflows were increased during this period. P budgets indicated that P may not currently be building up within Pineview Reservoir, but given the limited amount of ground water data available for the Reservoir’s watershed, further ground water flow and nutrient data are necessary to substantiate this claim. This study has helped to provide a clearer picture of the trophic status and internal P cycles of Pineview Reservoir. It has also helped to answer questions about the reservoir that have been overlooked in previous studies, such as the magnitude of internal P loading and the importance of Spring Creek and Geertsen Creek in the reservoir’s water budget. This and other information gathered during this study could prove to be a useful benchmark for measuring the effectiveness of future efforts to improve water quality in the reservoir.

Significant phosphorus transport is occurring in the groundwater surrounding Pineview Reservoir. A set of investigations was completed to identify factors contributing to phosphorus mobility. Water quality monitoring was conducted to understand groundwater characteristics and phosphorus movement. Several water quality parameters were evaluated to specifically determine whether septic systems influence groundwater quality. Results indicate that septic systems pollute at least two locations in the aquifer around the reservoir. Given this information, it may be necessary to implement advanced septic system treatment options to reduce the amount of phosphorus in groundwater. Experiments were conducted on two aquifer sediment types to identify factors important for phosphorus mobility. Coarse-grained sand and fine-grained sediments were evaluated, and results showed that phosphorus in both sediments is associated more with calcium minerals than with iron and aluminum minerals. Results suggest calcium is an important factor for immobilizing phosphorus in groundwater at Pineview Reservoir. Iron and manganese oxide concentrations are important for decreasing phosphorus mobility, and experiments showed higher amounts were observed in fine-grained sediments than for coarse-grained sediments. Results of geochemical modeling exercises suggested that sediments may have limited sorption capacity, although at one site, the formation of calcium minerals may provide a continuous source of additional sorption material. Because of suspected septic system influence, the effect of dissolved organic matter on phosphorus mobility was evaluated through a series of laboratory studies. Dissolved organic matter was collected from Pineview Reservoir and used in experiments. Results showed that the presence of dissolved organic matter affected phosphorus sorption minimally, and does not explain P mobility in the shallow unconfined aquifer at Pineview Reservoir.