Doctor of Philosophy, The Ohio State University, 2019, Environment and Natural Resources

Soil health is an emerging framework that seeks to integrate the physical, chemical, and biological components of soil. It is defined by the USDA as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans”. The breadth of this definition has allowed “soil health” to become a context-specific definition, letting soil health be defined in terms of the desired outcomes. In the context of agronomic nutrient management, the primary desired outcome is a tightening of the nutrient cycle to minimize losses to the environment. Here, I use the framework of soil health to understand how soil health indicators influence and are influenced by on-farm nutrient management practices. Three separate studies were conducted to: 1) understand the factors influencing the efficacy of the most widely used biological soil health metric, mineralizable carbon, 2) determine the effect of 12 years of phosphorus (P) restriction on biological and physical soil health in three Ohio sites, and 3) integrate biological soil health indicators into nitrogen (N) management strategies across the Corn Belt. The first study found that mineralizable C was variable across and within soil test labs. However, even after controlling for variations in methodology, a significant amount of the variability was soil-specific. The second study found very few effects of P restriction on soil biological and physical health. However, P restriction slightly increased organic P stocks and resulted in consistent shifts in the balance between the processed and easily-metabolized portions of the active C pool. In the third and final study, an increase in soil biological health was shown to increase the yields for a given N fertilization rate, as well as having slight predictive abilities in predicting whether a site would be responsive to N fertilization. This study also showed that soil biological health may be slightly increased at moderate N fertilization rates. C (open full item for complete abstract)

Committee: Steve Culman (Advisor); Michael Demyan (Committee Member); Kristin Mercer (Committee Member); Nicholas Basta (Committee Member); Jessica Logan (Committee Member) Subjects: Agronomy; Soil Sciences

Master of Science, The Ohio State University, 2019, Horticulture and Crop Science

Soybean agronomic optimum seeding rate (AOSR) varies from less than 200,000 seeds ha-1 to over 400,000 seeds ha-1 based on yield potential and environmental factors, and planting at or near the AOSR helps farmers maximize yield. Understanding where AOSR is likely to be high or low is useful for soybean farmers utilizing variable rate seeding. An AOSR representing an area smaller than a whole field is referred to as local ideal seeding rate (LISR). The objective of this on-farm study was to identify soil and terrain attributes that were most predictive of differences in LISR. Randomized, replicated seeding rate strip trials were established at 4 fields in 2017 and 3 fields in 2018. Yield data taken from yield monitors were used to estimate LISR 33 to 68 times per field. Soil physical and chemical properties were measured across the field using 0.2 hectare grid samples. In order to estimate soil fertility at the same scale as LISR, geographically weighted regression and random forest interpolation methods were compared. Geographically weighted regression (GWR) had lower root mean square error and better identified low-phosphorous areas of the field, so GWR was used to interpolate all soil properties. Terrain attributes calculated from 0.76 m digital elevation models were also summarized to this scale. Random forest analysis was performed to identify which soil and terrain attributes were most important for predicting LISR within each site-year. Terrain attributes were generally more important than soil properties at all site-years. Univariate linear models were used to relate the most important soil and terrain attributes to LISR. Valley depth was an important variable for model stability in multiple sites and had a strong univariate relationship with LISR across 7 site-years. Moving from the lowest valley to the highest ridge was associated with an LISR increase of 76,000 seeds ha-1. Aspect and relative slope position also had large univariate impacts on LISR. While (open full item for complete abstract)

Committee: Laura Lindsey (Advisor); John Fulton (Committee Member); Elizabeth Hawkins (Committee Member); Pierce Paul (Committee Member); Sakthi Subburayalu (Committee Member) Subjects: Agronomy; Soil Sciences

Master of Science, The Ohio State University, 2017, Horticulture and Crop Science

Ohio soybean farmers are very concerned about disease and insect pressure during the midseason that may impact yield. The impact of mid-season management for foliar diseases and insect feeding on grain yield was studied in a series of field experiments. The first objective was to evaluate the effect of mid-season foliar fungicide and insecticide application on soybean yield, applied alone or in combination. A trial was established at 12 on-farm field site-years in Ohio during 2015 and 2016 in a randomized complete block design with four replications per treatment. Fungicide and insecticide treatments included: 1) nontreated control, 2) fungicide alone, 3) insecticide alone, 4) fungicide plus insecticide (tank-mixed), 5) fungicide and insecticide (separate tank), 6) fungicide plus crop oil, 7) insecticide plus crop oil, 8) fungicide, insecticide plus crop oil (tank-mixed). All treatments were applied at R3 growth stage (initial pod development), and data on the percent leaf area affected by foliar diseases and insect defoliation was collected. There was no significant yield response associated with insecticide application due to low insect pressure and low insect defoliation levels at the time of insecticide application at all 12 site-years. However, at the end of the growing season, the number of bean leaf beetles (2-22) and pod injury caused by their feeding (4.1-37%) were high at 4 out of 12 site-years. Fungicide application alone had significantly (P<0.05) higher yield of 4 to 8 bushel/acre at 4 of 12 site-years due to the high leaf area affected in the canopy from Septoria glycines and Cercospora sojina which cause brown spot and frogeye leaf spot disease, respectively. The mean yield from plots treated with a tank-mixture of fungicide and insecticide was not significant difference from those treated with the fungicide alone. In this study, insecticide applications were applied too early in the growing season to have an impact on late-season pod feeding. Based o (open full item for complete abstract)

Committee: Laura Lindsey (Advisor); Anne Dorrance (Committee Member); Andrew Michel (Committee Member) Subjects: Agriculture; Agronomy; Entomology; Plant Pathology; Plant Sciences

Doctor of Philosophy, The Ohio State University, 2016, Environmental Science

Over 70% of Tanzanians live on less that $2 per day and over 75% of the population is involved in agriculture. Increasing agricultural productivity is seen as a way to decrease poverty and stimulate the economy. Sustainable Intensification (SI) is widely promoted as a means to sustainably increase agricultural production for smallholder farmers. Practices considered being SI should increase productivity on the same land with more efficient use of resources, in a way that minimizes negative effects on the environment. The objectives of these studies were to evaluate SI practices for their effect on agronomic productivity and soil quality for smallholder farmers in Tanzania. Further, these studies sought to identify the impact that these practices have on smallholder farmer profitability and water management within an irrigation scheme. These objectives were achieved through experiments carried out at three locations over three growing seasons within the Lower Moshi Irrigation Scheme (LMIS) in Mabogini Village, Kilimanjaro Region, United Republic of Tanzania. The studies each evaluated improved cropping systems that are appropriate for various areas within the scheme. The first three studies evaluated the System of Rice Intensification (SRI), crop rotations and nutrient management strategies, and reduced tillage for their effect on agronomic productivity and soil quality. Two further studies evaluated the profitability of SRI and the occurrence of dry spells in the region and the implications this has for rainfed maize (Zea mayes) production. Within continuous rice (Oryza sativa), SRI and conventional had similar yields to those under conventional practices in the region except for during the last season, in which SRI systems yielded on average 1.25 Mg ha-1 higher than conventional systems. If SRI is adopted throughout the LMIS, there is potential to increase rice production by 4,173 Mg due to increased water use efficiency and the ability to increase the area unde (open full item for complete abstract)

Committee: Lal Rattan (Advisor) Subjects: Agronomy; Soil Sciences

Doctor of Philosophy, The Ohio State University, 1955, Food, Agricultural and Biological Engineering

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Committee: Garth Volk (Advisor) Subjects: Agronomy

Master of Science, The Ohio State University, 2015, Horticulture and Crop Science

From 2000 to 2013 soybean [Glycine max (L.) Merr] grain commodity price has increased by almost 300% generating interest in agricultural inputs to maximize soybean yield. The objective of this study was to evaluate the effect of common inputs on soybean grain yield in enhanced (high-input) and traditional (low-input) production systems. The inputs evaluated included: Rhizobia inoculant, gypsum, pyraclostrobin fungicide, lambda-cyhalothrin insecticide, and manganese (Mn) foliar fertilizer. A sixteen site-year trial was established in Ohio during 2013 and 2014. Rhizobia inoculant was seed applied before planting, gypsum was applied at the VC growth stage (unrolled unifoliate leaves), and fungicide, insecticide, and Mn foliar fertilizer were applied at the R3 growth stage (initial pod development). Measurements of percent leaf area affected by foliar disease and insect defoliation and Mn and sulfur (S) concentration in leaves were collected at six site-years. The omission of pyraclostrobin from the enhanced production system significantly reduced yield in five of sixteen site-years by 0.21 to 0.79 Mg ha-1, but its addition to a traditional system increased yield significantly at only one of sixteen site-years by 0.47 Mg ha-1 Soybean yield was influenced by fungicide application when fields had disease present, above average yield (>3.5 Mg ha-1), and received >25 cm of precipitation in June and July. During 2013 and 2014, with established corn/soybean rotations, no S or Mn deficiencies, and minimal insect pressure, there were limited effects of inoculant, gypsum, insecticide, and Mn foliar fertilizer on grain yield. The data indicate a very small potential for high-input production systems to enhance crop yield without the presence of diseases, insects, or nutrient deficiencies. Knowledge of potential yield limiting factors is useful in identifying inputs that will increase soybean yield on a field by field basis.

Committee: Laura Lindsey (Advisor); Anne Dorrance (Committee Member); Jim Metzger (Committee Member) Subjects: Agriculture; Agronomy; Plant Pathology; Plant Sciences

Master of Science (MS), Ohio University, 2013, Environmental Studies (Voinovich)

This thesis will explore several pertinent issues regarding environmental sustainability that arise in the recent work of James C. Scott, a professor of Anthropology and Political Science at Yale University. As a result of his official academic titles, fellow scholars overlook the applicability of Scott's work to contemporary issues in environmental studies. But even though his academic pedigree might seem an odd mix from which to cull salient insights into issues of environmental sustainability, this thesis will show that Scott's interdisciplinary background gives him a uniquely advantageous vantage point from which to explore environmental issues. Scott's work offers a panoply of insights that strike at the root of many environmental problems. Chief among his inquiries is the state's role in instigating ecological catastrophe. Scott's analysis of this role is so penetrating and comprehensive that it prompts readers to question the compatibility between the existence of states and prospects for environmental sustainability. The briefest encapsulation of Scott's argument is that states invariably — and perhaps necessarily endeavor to organize existence, and that this organizational compulsion disrupts natural ecological flows, thus producing dire consequences for biota. A second, related insight is that human groups who strive to resist the state invariably — and perhaps necessarily exhibit a more balanced, harmonious commingling with the natural order. The conscious evasion of state-like structures among stateless peoples compels them to apply a set of practices that reduce their environmental impact to nearly nil. These dual insights deserve careful attention given that environmental issues have been thrust to the forefront of social life in recent years. Accordingly, one purpose of this thesis is to recast Scott as one of the most relevant thinkers who can contribute to the conversation regarding sustainability. A second purpose of this thesis is to surve (open full item for complete abstract)

Committee: Julie White (Committee Chair); DeLysa Burnier (Committee Member); Nancy Manring (Committee Member) Subjects: Environmental Justice; Environmental Philosophy; Environmental Studies; History; Native Studies; Philosophy; Political Science

Doctor of Philosophy, The Ohio State University, 2010, Soil Science

This dissertation is comprised of three separate studies in soil science and fertility. The first component concerns the use of swine manure on a leguminous crop. Recent environmental pressure has been placed to limit the practice of applying animal manures to fields planned for soybean [Glycine max (L.) Merr] production because of the perceived hazard of excessive NO3 movement offsite. The objective is to evaluate the impact of manure application to soybean fields on soil NO3-N, N uptake and soybean crop productivity. A field experiment was established in the spring of 2007 and 2008. Liquid swine (Sus scrofa domestica) manure was applied at three different N rates (based upon manure analysis and estimated availability) using two application methods (surface application or injection). Commercial fertilizer treatments (same equivalent rates) were also included as positive controls. Soil samples to 60 cm and tissue samples were collected throughout the growing season. Even though N application did result in higher soil NO3- levels for some treatments, applications rates that were less than or equal to 135 kg ha-1 represented a lower risk of possible NO3-N movement. Nitrogen supplied via manure and commercial fertilizer resulted in larger N uptake than the controls, but grain yield was not improved. This reveals that despite the fact that soybeans can fix their own N, soybeans will absorb soil inorganic-N as a net N sink. The second chapter of the dissertation explores the interactions of foliar-applied manganese and the herbicide glyphosate on glyphosate-resistant weeds. Glyphosate is a metal chelating agent that interacts with cations essential to plant growth, and previous studies have shown interactions with Mn resulting in decreased herbicide efficacy and manganese metabolism issues. This study measured the effects of different formulations of glyphosate and manganese combinations as well as timing of the application. Of six site-years, one instance of manganese a (open full item for complete abstract)

Committee: Robert Mullen PhD (Advisor); Edward McCoy PhD (Committee Member); Peter Thomison PhD (Committee Member); Mark Loux PhD (Committee Member) Subjects: Agricultural Chemicals; Agriculture; Agronomy; Soil Sciences