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Browsing by Author "Bohman, Brian"

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    Banking Groundwater - A study examining aquifer storage and recovery for groundwater sustainability in Minnesota
    Bilotta, John P.; Arnold, William; Kang, Peter; Seonkyoo, Yoon; Shandilya, Raghwendra N.; Bresciani, Etienne; Lee, Seunghak; Kirk, Josh; Levers, Lucia; Bohman, Brian; Kirby, Eileen; Runkel, Anthony; Xiang, Galen; Gassman, Phillip; Valcu-Lisman, Adriana; Jennings, Carrie E.; jbilotta@umn.edu; Bilotta, John P; University of Minnesota Water Resources Center; Freshwater
    Some of the more than 75% of Minnesotans who rely on groundwater may find it in short supply in the face of population, land-use and climate change. Aquifer storage and recovery (ASR) is a technological approach to treat and inject clean water into an aquifer for temporary storage. The hydrogeological characteristics and the chemistry of the source water and aquifer impact treatment needs prior to injection and after extraction. Aquifer properties that control how water moves determine the volume and rate of water injected. This study examined four different kinds of aquifers across Minnesota with unique pressures to determine their suitability for ASR. The study findings suggest three may be suitable for ASR. The Buffalo aquifer in Moorhead has variable injection capacity and multiple sources of water for injection. Water quality issues of arsenic, sulfate, manganese, and hardness would require treatment after extraction. The Jordan aquifer in Rochester faces increased pressure from growth and nitrate contamination in the surrounding agricultural areas. The wastewater treatment plant could provide adequate source water if treated. Woodbury faces pressure from increasing population and PFAS contamination of the Jordan aquifer. ASR could recharge groundwater from wastewater treatment plants and also be integrated with PFAS remediation scenarios by reinjection of treated groundwater. ASR is not recommended for the surficial sand aquifer in the Straight River Groundwater Management area in north central Minnesota because there is no source of water to make it a feasible option at this time. Cost-benefit analysis combined with a sensitivity analysis of economic factors should be a component of ASR project feasibility. Modified state well code and a streamlined permitting path would allow more successful development and deployment of ASR. State adoption of control over Class V injection wells from the USEPA is also necessary.
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    Investigating Nitrogen and Irrigation Management Strategies to Improve Agronomic and Environmental Outcomes for Potato Production
    (2021-08) Bohman, Brian
    Nitrogen [N] fertilizer and irrigation management practices are both critical factors for determining agronomic and environmental outcomes for potato [Solanum tuberosum (L.)] production. This dissertation was comprised of two overall objectives. First, a small-plot experiment evaluating the effects of six N rate, source, and timing treatments and two irrigation rate treatments on tuber yield, quality, net profitability, nitrate leaching, residual soil nitrate, plant N uptake, N nutrition index [NNI], N uptake efficiency, N utilization efficiency [NUtE], N use efficiency [NUE], biomass, harvest index, biomass, and potential N losses for potato [cv. ‘Russet Burbank’] were investigated in 2016 and 2017 at Becker, MN, on a Hubbard loamy sand. Conventional N fertilizer best management practices [BMPs] (270 kg N ha-1) were compared to reduced N rate (180 kg N ha-1), control N rate (45 kg N ha-1), and a variable rate [VR] N treatment based on the N sufficiency index [NSI] approach using remote sensing. Irrigation treatments included a conventional rate (100%) based on the “checkbook” method and a reduced rate (85%). The VR treatment reduced N applied relative to the recommended rate by 22 and 44 kg N ha−1 in 2016 and 2017, respectively. Irrigation rate was reduced by 29 and 33 mm in 2016 and 2017, respectively. From an agronomic perspective, neither VR N nor reduced irrigation produced significant differences in tuber yield or net return compared to full rate treatments. From an environmental perspective, nitrate leaching losses varied between 2016 and 2017 with flow-weighted mean nitrate N concentrations of 5.6 and 12.8 mg N L−1, respectively, and increased from 7.1 to 10.4 mg N L−1 as N rate increased from 45 to 270 kg N ha−1. Despite reductions in N rate for the VR N treatment, there was no significant difference in nitrate leaching compared with the existing N best management practices (BMPs). However, reducing irrigation rate by 15% decreased nitrate leaching load by 17% through a reduction in percolation. Second, an evaluation of the relationship between NUE, NNI, and their variation across genotype [G] x environment [E] effects was conducted. A novel theoretical relationship between NNI and NUtE was derived: at a constant NNI value, NUtE values increased non-linearly as biomass increased, and at an NNI value of 1.0 this relationship defines the critical N utilization efficiency curve [CNUtEC]. Subsequently, an evaluation of the variation in critical N concentration [%Nc] was conducted using a hierarchical Bayesian framework to infer the critical N dilution curve [CNDC] across G x E effects observed from multiple experimental trials. This statistical method was able to quantify the uncertainty in %Nc, which was used to directly compare CNDCs. Critical N concentration was found to significantly vary across the effect of E, and in some cases for G within E. Therefore, consideration of both NNI and NUE require explicit consideration of the uncertainty in and variation due to G x E effects for %Nc. Overall, the findings of this dissertation improve both the empirical and theoretical understanding of the impact of N fertilizer and irrigation management practices on agronomic and environmental outcomes for potato.