Doctor of Philosophy, The Ohio State University, 2021, Horticulture and Crop Science

The emerging craft brewing industry has created a demand for high-quality local malting barley (Hordeum vulgare L.) grain, generating interest among farmers. Winter malting barley is a relatively new crop to the Ohio and Midwest region, requiring agronomic recommendations for production to meet the malting industry's quality parameters of protein (95 to 125 g kg-1), deoxynivalenol (DON) (≤1 mg kg-1), plumpness (90% of kernels to exceed 2.57 mm size), and germination (>95%), while increasing grain yield. Farmers are faced with climatic challenges of extreme temperature fluctuations during the winter and saturated soils in the spring, potentially injuring malting barley plants. Four experiments were conducted in Ohio during 2017-21, to evaluate the effects of seeding rate and companion cover crops on winter malting barley yield and quality, and the use of fractional green canopy cover (FGCC) to estimate grain yield. The objectives of the research were to 1) identify the agronomic optimum seeding rate (AOSR), where grain yield is maximized, and identify the seeding rate that meets or exceeds grain quality parameters of low protein and DON levels and high plumpness and germination of the grain, 2) evaluate the relationships between spring stem counts, fractional green canopy cover (FGCC), normalized difference vegetation index (NDVI) and barley grain yield, 3) conduct on-farm research to use FGCC percentages measured with the mobile smartphone application, Canopeo, and manual stem counts by hand to estimate winter malting barley grain yield in the spring, and 4) determine the effects of three companion cover crops, oats (Avena sativa L.), crimson clover (Trifolium incarnatum L.), and oilseed radish (Raphanus sativus L.), and their seeding date on the yield and quality of a two-row winter malting barley cultivar, ‘Puffin'. In the first study, from 2017-20, five seeding rate treatments ranging from 1.9 to 6.2 million seeds ha-1 were established at Custar, South Charleston (open full item for complete abstract)

Committee: Laura Lindsey (Advisor); Steve Culman (Committee Member); Eric Stockinger (Committee Member); Stephen Jacquemin (Committee Member); Elizabeth Hawkins (Committee Member) Subjects: Agriculture; Agronomy

Master of Science, The Ohio State University, 2021, Food, Agricultural and Biological Engineering

Common agricultural practices are leading to widespread soil degradation and poor soil health in the U.S., lowering agricultural productivity, increasing water quality concerns, and threatening the resilience of the agricultural systems to increasing climate variability. According to the Ohio Environmental Protection Agency, approximately 48% of Ohio's watersheds are degraded by nutrient (phosphorus and nitrogen) loading from various sources including agricultural fields. This has resulted in increasing occurrences of harmful algal blooms in Lake Erie and inland lakes, creating several environmental, and socio-economic issues such as degradation of aquatic habitat, poor drinking water, and increased cost for water treatments. Cover cropping is one of the conservation practices which has potential to reduce soil erosion and nutrient runoffs from agricultural fields while improving or maintaining soil health. Although prior works have focused on cover crops and their impacts on soil health and water quality, they are based mainly on controlled field experimental trials. Currently, there is a limited understanding of spatial and temporal trend in cover cropping practices and their impacts at a landscape scale. Thus, the objective of this study is to develop a spatial and temporal inventory of winter cover cropping practices and assess their impacts on crop productivity and water quality in the Western Lake Erie basin. A Random Forest classification model was built upon field collected cover crop data and a long-term seasonal composites of satellite images (Landsat 5, 7, and 8) focusing on winter cover crop growing season from 2008 to 2019. The model was focused mainly on corn and soybean fields, and the information about corn and soybean fields on an annual scale was obtained from USDA cropland data layers which was then used to classify the fields into four categories – (1) Winter kill, (2) Winter hardy (3) Spring emergent, and (4) Not covered. The annual cover croppi (open full item for complete abstract)

Committee: Sami Khanal (Advisor); Kaiguang Zhao (Committee Member) Subjects: Agricultural Engineering

Master of Science, The Ohio State University, 2019, Environment and Natural Resources

Conservation practices, such as no-till and diversifying crop rotations are known for their capacity to reduce soil erosion and improve soil properties. However, the impact of these management practices on emerging soil health tests and the ability of these tests to reflect active organic matter dynamics and nutrient cycling, and corn productivity has not been explored. This project focused on determining the effects of half a century of continuous tillage treatments (moldboard plow, chisel till, and no-till) and crop rotations (continuous corn, corn-soybean, and corn-forage-forage) on soil health indicators and its relationship with crop productivity. The forages were alfalfa in Wooster and red clover and oats in Northwest. Soil labile carbon (C) and nitrogen (N) temporal dynamics were quantified with permanganate oxidizable C (POXC), mineralizable carbon (Min C), and soil protein at six key stages in corn (Zea mays) development: before planting (around three weeks before planting), V5, V10, R1, R4, R6 in the 2017 and 2018 growing seasons. Corn leaf chlorophyll, aboveground plant biomass, nutrient uptake, and grain yield were also quantified. The soil health indicators (POXC, Min C, soil protein) and crop parameters (leaf chlorophyll, total nitrogen uptake, and total aboveground biomass) were higher in reduced tillage (chisel and no-till) compared to moldboard plow and higher in the most diverse crop rotation (corn-forage-forage) compared to corn-soybean. Corn yields were not significantly different between tillage treatments but were higher in the more diverse rotations (corn-soybean and corn-forage-forage) compared to corn monoculture. Although the treatment effects varied by site and year, rotation had a consistently larger effect on soil health indicators and corn productivity than tillage, highlighting the importance of including crop rotations in corn production. We conclude that Ohio soils under half a century of continuous tillage and rotation treatments ha (open full item for complete abstract)

Committee: Steve Culman PhD (Advisor); M.Scott Demyan PhD (Committee Member); Peter Thomison PhD (Committee Member) Subjects: Agriculture; Agronomy; Soil Sciences

Ph.D., Antioch University, 2018, Antioch New England: Environmental Studies

Climate change and crop intensification are key challenges to the livelihoods and wellbeing of the majority of rural smallholder farmers in developing countries, particularly in human-dominated, climate-sensitive landscapes such as the northern highlands of Rwanda where issues of fluvial floods, soil erosion pose serious threats to the livelihoods of smallholder farmers. In this mixed methods study conducted between August and December 2015, I explored smallholder farmers' perceptions by examining what barriers might hinder the process of agroforestry adoption by smallholder farmers, what socio-economic and physical factors and attitudes influence crop choices, motivations for smallholder farmers' willingness to plant trees within riparian buffer zones and opportunities and challenges to the establishment of riparian buffer zones that maintain ecosystem services. Results indicate that challenges to adoption of agroforestry to support climate change adaptation and food security in Rwanda are related to land scarcity, poverty, limited technological and financial capacity among most smallholder farmers, limited engagement of smallholder farmers in agroforestry research and an inclination for short term benefits that could hinder adoption of agroforestry which has a long term investment. Most smallholder farmers believed that the onset of short rains comes earlier in recent years compared to more than ten years ago. In response, most farmers reported that they plant crops earlier in the season. Results from rainfall analysis, although not conclusive, show a shift in rainy day frequency. Respondents who strongly agreed that soil erosion within farms proximal to streams is a serious threat were more likely to support the idea that establishing a riparian buffer would help entrap sediments and mitigate soil erosion within farmlands adjacent to streams. However, farmers reported that establishing a functional riparian buffer requires engagement with extension services, fi (open full item for complete abstract)

Committee: Beth Kaplin Ph.D. (Committee Chair); James Gruber Ph.D. (Committee Member); Joel Hartter Ph.D. (Committee Member) Subjects: Agriculture; Environmental Management; Environmental Science; Environmental Studies; Forestry; Water Resource Management

Master of Science, The Ohio State University, 2018, Horticulture and Crop Science

In Ohio, many organic farmers use the term `balancing' to express the rationale of using a wide variety of soil amendments to improve soil quality and plant health. Soil balancing or the base cation saturation ratio (BCSR) approach is a method first proposed more than 100 years ago that aims to achieve the `ideal soil'. William Albrecht in the 1970's concluded that if saturation of the major exchangeable cations is 65-85% for Ca, 6-12% for Mg, and 2-5% for K, plant nutrition will be balanced. Research conducted by Zwickle et al. (2011) indicated that many organic farmers believe balanced soils produce higher quality crops and have diminished weed infestations compared to unbalanced soils. For many farmers, soil balancing includes using amendments thought to enhance soil biology and increase the soil's capacity to store and release minerals needed by plants. Combined mineral and these organic/bio-active soil products can be very costly, as much as US $1000-1250/ha in the first year. While farmers believe they are benefiting from these expenditures, there is no objective evidence to confirm their belief. I conducted on-farm studies at six locations in Northeast Ohio, with the overall goal of determining the effect of gypsum, with or without “biological stimulants”, on the soil microbial community, crop quality, weed populations, and soil chemical characteristics. Soil seed bank and soil health/biological properties were measured, including soil respiration, active carbon, protein content, microbial biomass, and complete mineral analysis. Crop foliage for nutrient analysis, and crop quality was determined after harvest. Differences in final soil nutrient levels, base saturation, crop and weed community effects were influenced more by the farm than by the treatments applied. After two years, soil sulfur levels were significantly higher in plots amended with gypsum. Failure to detect treatment response by other mineral amendments suggests the relatively narrow difference (open full item for complete abstract)

Committee: Douglas Doohan (Advisor); Warren DIck (Committee Member); Kleinhenz Matthew (Committee Member); Steve Culman (Committee Member) Subjects: Agriculture; Horticulture; Soil Sciences

Master of Science, The Ohio State University, 2008, Horticulture and Crop Science

Many benefits of crop rotational systems have been documented, but little information is available regarding the potential of crop and livestock grazing rotations in the US Corn Belt. The objective of this research was to study changes in soil properties, crop production and animal performance in a no-till integrated crop-livestock system. Three cover crop treatments were planted after corn silage harvest: annual ryegrass, an oat + rye mixture, and a no cover crop control. Cover crops were grazed by dairy heifers in autumn 2006 and spring 2007. Forage yield was greater for oat + rye, resulting in greater animal carrying capacity than annual ryegrass in spring 2007, autumn 2007 and spring 2008, but not in autumn 2006. Animal traffic from grazing increased soil penetration resistance compared with the ungrazed control; however, no differences in subsequent silage corn yield were found among treatments. Both cover crop treatments had greater root yield, soil microbial flush, and particulate organic carbon concentrations in the 0 to 15 cm soil depth than the no cover crop control. The integration of a cover crop into corn silage production in Ohio has the potential to provide additional livestock grazing and increase labile soil carbon without detrimental effects on subsequent corn silage productivity provided grazing is carefully managed.

Committee: R. Mark Sulc Dr. (Advisor); David J. Barker Dr. (Committee Member); Richard P. Dick Dr. (Committee Member); Maurice L. Eastridge Dr. (Committee Member) Subjects: Agriculture; Agronomy; Ecology; Livestock; Soil Sciences