About

Greg Roth is an Emeritus Professor of Agronomy at Pennsylvania State University with a focus on grain crop management. His expertise includes managing corn, soybean, winter wheat, and winter barley, as well as evaluating hybrids and varieties for yield and quality traits. Roth develops educational programs for extension agents, agribusiness groups, and producers on issues such as drought stress management, GMO concerns, specialty crop hybrids, grain quality, organic grain production, and silage production. He conducts applied field research on crop management strategies, including managing corn for silage and evaluating transgenic hybrids for regional adaptability. Roth is also involved in developing innovative methods such as interseeding cover crops into growing corn and assessing the profitability of various management practices. His work aims to create more opportunities for crop producers and improve sustainable agricultural practices.

Research topics

• Biology
• Agronomy
• Chemistry
• Food science
• Animal science
• Biochemistry
• Ecology
• Toxicology
• Horticulture

Selected publications

• Cardiovascular disease in the Americas: the epidemiology of cardiovascular disease and its risk factors

  The Lancet Regional Health - Americas · 2025-02-01 · 38 citations

  reviewOpen access

  This first article of the Series about Cardiovascular Disease in the Americas summarizes the epidemiology of CVD and its risk factors, and population-level strategies in place aimed at CVD prevention. While age-standardized CVD incidence and CV mortality rates have been decreasing across in the Americas since 1990, the annual number of CVD cases and related deaths have increased due to population growth and ageing. The burden of CVD is also slowly transitioning from high-income countries in North America to middle-income countries in Latin America and the Caribbean. Trends in CV risk factor levels have been mixed, with declines in smoking and mean cholesterol counterbalanced by higher prevalence of obesity and diabetes. Population-wide strategies aimed at controlling cardiometabolic risk factors and tobacco use have been implemented with varying degrees of success. There is a need to better implement existing CVD prevention strategies in the region.

  PublisherDOI

• Corrigendum to “Lactational performance of dairy cows fed diets based on corn silages varying in ruminal degradability of starch and fiber” (J. Dairy Sci. 108:5765–5785)

  Journal of Dairy Science · 2025-10-01

  articleOpen access
  PublisherOA PDFDOI

• Lactational performance of dairy cows fed diets based on corn silages varying in ruminal degradability of starch and fiber

  Journal of Dairy Science · 2025-05-21

  articleOpen access

  <h2>ABSTRACT</h2> Corn silage (CS) is a cornerstone component in dairy cattle diets, contributing up to 50% of the total dietary NEL intake. Selecting high-quality CS hybrids is critical for improving production efficiency and reducing the carbon footprint of dairy operations. The rumen fermentable organic matter index (RFOMI) assesses CS nutritional quality, with a focus on rumen fermentable NDF (RFNDF) and starch (RFST), which together account for the majority of digestible silage OM. The objective was to evaluate the effects of feeding CS with similar RFOMI but varying RFST and RFNDF contents on lactational performance, enteric gas emissions, nutrient digestibility, and nitrogen utilization in dairy cows. Rumen fermentable NDF and RFST were determined using established in vitro and in situ methods, incorporating digestibility coefficients and nutrient fraction analyses. A total of 48 mid-lactation Holstein cows (16 primiparous, 32 multiparous) were used in this study. Post-ensiling RFST to RFNDF ratios (RFST:RFNDF) in CS were used for treatment designation. The study was a randomized complete block design where cows within a block were randomly assigned to treatment diets. The diets were fed as TMR and contained 50% CS (dietary DM basis) with RFST:RFNDF of 1.62, 1.85, 1.92, or 2.08. Animal performance and enteric gas emissions were evaluated using polynomial linear or quadratic effects of postfermentation CS RFST:RFNDF ratios. A quadratic effect of treatment on DMI was observed, where cows fed CS with the lowest RFST:RFNDF ratio resulted in the greatest DMI. Dairy cows fed CS with an increasing RFST:RFNDF ratio tended to have increased milk yield, but no effects were observed on ECM yield. Increasing RFST:RFNDF of CS in the diet increased quadratically feed and ECM feed efficiencies, CH₄ emission yield (as g/kg DMI), and total-tract DM and OM digestibilities. These results indicated that feeding CS with RFST:RFNDF ratios within 1.85 to 1.92, when compared with CS hybrids outside that range of RFST: RFNDF, at 50% of dietary DM, may promote a reduction in DMI but increase feed and ECM feed efficiencies andCH₄ yield by enhancing apparent total-tract DM digestibility in lactating dairy cows.

  PublisherOA PDFDOI

• Severe storm damage and short‐term weather stresses on corn: A review

  Crop Science · 2024-02-28 · 20 citations

  reviewOpen access

  Abstract Adverse weather conditions from acute events (e.g., storms causing lodging, flooding, or hail) or short‐duration weather patterns (i.e., periods of cold events; extended waterlogged field conditions) can result in yield losses, though management practices may play key roles in aiding with crop recovery or avoidance of these stress events. This review summarizes current knowledge (with emphasis placed on the US Midwest) related to corn response to short‐term weather stresses of (i) cold temperature, (ii) excess water, (iii) hail/defoliation damage, and (iv) wind damage. Each section presents summaries of how corn growth and yield are affected, provides context into past events experienced, identifies agronomic or production recommendations to correct or alleviate the stress condition, and proposes areas where future research is needed. This review also highlights challenges associated with controlled simulation work on these stressors, and also identifies key areas to expand future research efforts. In general, yield losses associated with strong storms and short‐term weather events often ranged from 5% to 35%, but extreme cases could result in up to 80%–100% yield loss. Much of the literature on these topics was published prior to 1995, though it still forms the basis for modern agronomic guidance, which is problematic given the changes in agriculture in the last 20 years in management practices, available genetics and technologies, and changing environmental conditions. Revisiting these foundational studies and expanding them to examine current and future weather conditions are critical for better informing agronomic recommendations, for devising mitigation strategies, and for determining accurate yield loss expectations following these stresses.

  PublisherOA PDFDOI

• Corn Disease Loss Estimates from the United States and Ontario, Canada — 2023

  2024-03-12 · 4 citations

  report
  PublisherDOI

• Soybean Disease Loss Estimates from the United States and Ontario, Canada — 2023

  2024-03-14 · 4 citations

  report
  PublisherDOI

• Effects of ensiling time on corn silage starch ruminal degradability evaluated in situ or in vitro

  Journal of Dairy Science · 2023 · 18 citations

  • Chemistry
  • Animal science
  • Food science

  Accurate measurements of concentration and ruminal degradability of corn silage starch is necessary for formulation of diets that meet the energy requirements of dairy cows. Five corn silage hybrids ensiled for 0 (unfermented), 30, 60, 120, and 150 d were used to determine the effects of ensiling time on starch degradability of corn silage. In addition, the effects of grind size of silage samples on 7-h in vitro starch degradability and the relationship between in vitro, in situ and near-infrared reflectance spectroscopy (NIRS) starch degradability were studied. In situ disappearance of corn silage starch increased from 0 to 150 d of ensiling, primarily as a result of an increase in the washout or rapidly degraded fraction of starch, particularly during the first 60 d of ensiling. When analyzed in vitro and by NIRS, ensiling time increased corn silage starch degradability either linearly or to a greater extent during the first 2 mo of ensiling. Differences in in situ starch disappearance among corn silage hybrids were apparent during the first 2 mo of ensiling but were attenuated as silages aged. No differences among hybrids were detected using a 7-h in vitro starch digestibility approach. Results from the in vitro subexperiment indicate that 7-h in vitro starch degradability was increased by reducing grind size of corn silage from 4 to 1 mm, regardless of ensiling duration. Fine grinding corn silages samples (i.e., 1-mm sieve) allowed distinguishing low- from medium- and high-starch degradability rated hybrids. Correlations among in situ, in vitro and NIRS measurements for starch degradability were medium to high (r ≥0.57); however, agreement among methods was low (concordance correlation coefficient ≤0.15). In conclusion, ensiling time linearly increased degradation rate of corn silage resulting in greater in situ starch disappearance after 150 d of ensiling. Reductions in grind size from 4 to 1 mm resulted in greater in vitro starch degradability, regardless of ensiling duration. Strong correlation but low agreement between starch degradability methods suggest that absolute estimations of corn silage starch degradability will vary, but all methods can be used to assess the effect of ensiling time on starch degradability.

  PublisherOA PDFDOI

• Are polycultures for silage pragmatic medleys or gallimaufries?

  Agronomy Journal · 2021-01-15 · 2 citations

  articleOpen accessCorresponding

  Abstract Polycultures, mixtures of different crop species in the same field, may provide both production and ecological benefits. Silage production in annual cropping systems may incorporate polycultures and take advantage of species’ niche partitioning, potentially stabilizing yield variation due to abiotic stress. Using maize ( Zea mays L.) silage as the basis of our 3‐yr study, we tested the impact on crop and soil attributes of replacing a fraction of maize with soy [ Glycine max (L.) Merr.], sorghum ( Sorghum bicolor var. bicolor × bicolor and var. sudanense [unnamed hybrid]), or a medley of soy, sorghum, and sunflower ( Helianthus annuus L.). Compared to maize monocultures and on average for the 3 yr, a replacement mixture of maize + soy lowered yields (1.57 vs. 1.87 kg m –2 ), but increased the N, P, and K concentration in the silage by 1.2x, 1.09x, and 1.03x, respectively. Maize + sorghum polycultures matched the biomass yields of maize monocultures (1.77 vs. 1.87 kg m –2 ) and increased K concentration (10.2 vs. 8.2 g kg –1 ). While random forest analysis revealed no change in post‐harvest soil mineral N with depth among treatments, there was a tendency for higher total mineral N left in the soil for soy‐containing vs. sorghum‐containing treatments (12.4 vs. 10.9 g m –2 ). Silage polycultures are a feasible alternative to maize silage monocultures and can improve silage nutrient concentration with no yield penalty if maize or sorghum dominate plant stands.

  PublisherDOI

• Lactational performance, rumen fermentation, and enteric methane emission of dairy cows fed an amylase-enabled corn silage

  Journal of Dairy Science · 2021 · 24 citations

  • Animal science
  • Chemistry
  • Biology

  emission intensity, compared with the control silage.

  PublisherOA PDFDOI

• Wheat intraspecific diversity suppressed diseases with subdued yield, economic return and arthropod predation services

  Agriculture Ecosystems & Environment · 2021 · 9 citations

  • Agronomy
  • Biology
  • Toxicology
  PublisherOA PDFDOI

Frequent coauthors

• A.N. Hristov

  Pennsylvania State University

  10 shared

• M.T. Harper

  Garvan Institute of Medical Research

  8 shared

• J. Oh

  5 shared

• R. H. Fox

  5 shared

• F. Giallongo

  Pennsylvania State University

  4 shared

• Harold G. Marshall

  Old Dominion University

  4 shared

• C. Alan Rotz

  4 shared

• Joseph G. Lauer

  University of Wisconsin–Madison

  4 shared

Education

• Ph.D.

  The Pennsylvania State University

  1987

• M.S.

  Virginia Polytechnic Institute and State University

  1981

• B.S., Agronomy

  The Pennsylvania State University

  1979