About

Allen Barker is a Professor of Plant and Soil Sciences at the University of Massachusetts Amherst, with a long-standing academic appointment starting from 1962. His educational background includes a B.S. from the University of Illinois, an M.S. and Ph.D. from Cornell University. Barker has held various academic positions at UMass Amherst, including Assistant Professor, Associate Professor, and Professor, and served as the Head of the Department of Plant and Soil Sciences from 1977 to 1985. His research focuses on plant nutrition, soil fertility, organic farming, and plant-soil interactions. Barker has contributed extensively to the field through teaching courses such as Plant Nutrition, Soil Fertility, Organic Farming and Gardening, and Plant Nutrients. He has received numerous honors and awards, including the Environmental Quality Research Award, Marion Meadows Award, and recognition as an Outstanding Teacher and Professor. Barker has also served in leadership roles within his department and professional organizations, including as Head of Department, Graduate Program Director, and Honors Coordinator. His professional memberships include the American Society of Agronomy, American Society for Horticultural Science, and other related societies.

Research topics

• Biology
• Agronomy
• Botany
• Horticulture
• Chemistry
• Mineralogy
• Environmental science
• Art
• Ecology

Selected publications

• Breaking of Seed Dormancy in Redroot Pigweed

  Communications in Soil Science and Plant Analysis · 2025-05-20

  articleSenior authorCorresponding
  PublisherDOI

• Physicochemical evolution of sugar maple biochar: Insights from a long‐term field trial

  Journal of Environmental Quality · 2025-06-29

  articleOpen access

  Abstract Biochars are recognized for their ability to sequester carbon, improve soil Ph, and reduce aluminum toxicity in acidic soils. This study investigated the changes in a hardwood (sugar maple, Acer saccharum ) biochar after long‐term aging in the soil, and its impact on the growth of soybean and on soil pH and available aluminum concentrations. An agricultural soil was treated with five different levels of biochar equivalent to 0, 40, 80, 120, and 160 Mg ha −1 , in separated plots, using a randomized complete block design (RCBD) with five replications across three growing seasons. The ash content and pH of the aged biochar were significantly reduced (72% and 1.2 units, respectively). The decline in soil pH increased soil‐available aluminum concentration. Additionally, the surface area and pore volume of aged biochar decreased by 69% and 61%, respectively, while the pore size in the aged biochar increased by 27%. Elemental analysis showed that as biochar aged, it was oxidized, decreasing its H:C ratio and increasing its O:C ratio. Furthermore, increased oxidation caused its surface charge to become more negative, with the zeta potential decreasing from −24 to −39.4 mV. Despite substantial changes to the biochar properties with aging, there was no significant effect on soybean yield. The goal of this project is to understand how biochar changes over time in the soil, its effects on soil health and aluminum toxicity, and whether it continues to benefit crops like soybeans, helping farmers and researchers make sustainable decisions about its long‐term use.

  PublisherOA PDFDOI

• Weed Control with Crop Residues in Vegetable Cropping Systems

  2024-12-09

  book-chapter1st authorCorresponding

  Summary. Crop residues have many potential uses in cropping systems, among which are imparting weed control. The principal objective of this research was to evaluate residues from corn (Zea mays L.), soybean (Glycine max Merr.), and sunflower (Helianthus anmuts L.) for their effects on weed control and on crop productivity of tomato (Lycopersicon escalentum Mill.) and summer squash (Cucumispepo L. var. melopepo Alef.). In one experiment, residues were imported to the vegetable plots and applied as surface mulches or incorporated shallowly into the ground. In another experiment, the residues were grown on site as cover crops in the year preceding vegetable production and disked into the plots. Application of imported residues was more effective in weed control and yield enhancement than the cover crop residues. Imported residues were effective in control of early emerging weeds, whereas with the cover crops supplemental weed management was required for early weed control. Weed control did not differ substantially with species of residue, but control increased as amount of incorporated residues increased from 6 to 24 Mg/ha. Weed control with residue incorporation at 6 Mg/ha was as effective as a mulch of 24 164Mg/ha. If weed control was imparted by the residues, crop yields with any residue treatment were equivalent to those from plots kept relatively weed-free by tillage. Yields did not vary with amounts of residues applied. Weed control by the residues was effective in growing seasons or months of growing seasons with below-normal or near-normal rainfall. High rainfall destroyed the weed-controlling potential of the mulched or incorporated imported residues or cover crop residues. This research demonstrated that crop residues impart weed control and that in years with adequate control, yields of crops will be equal to those in plots with rigorous control by tillage. In times of high rainfall during crop production or with use of residues from cover crops, supplemental weed management practices will be needed. [Article copies available for a fee from The Haworth Document Delivery Service: 1-800-342-9678. E-mail address: < https://www.w3.org/1999/xlink" xlink:href="https://getinfofwhaworthpressinc.com">getinfofwhaworthpressinc.com > Website: < https://www.HaworthPress.com > © 2001 by The Haworth Press, Inc. All rights reserved.]

  PublisherDOI

• Enhancing nitrate and ammonium recovery from lettuce leaves: evaluating the impact of cultivation practices and chemical extractants

  Journal of Plant Nutrition · 2024-04-02

  article

  This study aimed to identify what affects mineral nitrogen (N) levels in lettuce by testing how different chemicals extract nitrate and ammonium, using continuous flow analysis for measurement. The study's rationale is to explore how agricultural methods and environmental factors impact the nutrition and safety of leafy greens. In this research, we utilized a collection of lettuce leaf samples obtained from our earlier investigation. The study involved examining different cultivars cultivated in diverse fields or greenhouse settings, using organic or conventional fertilizers, to observe the outcomes. To measure the amount of ammonium in leaf tissue, we assessed extraction solutions of 0.001, 0.01, 0.1, 1.0, and 2.0 M potassium chloride (KCl), along with distilled water. These evaluations were conducted using leaves from 16 different lettuce plants cultivated under various production conditions. To quantify nitrate, extracting solutions of 0.01 M calcium chloride (CaCl2), 2% acetic acid, and distilled water with two contact times (15 and 45 min) were evaluated. Increasing contact time increased the recovery of nitrate. Distilled water and calcium chloride were significantly more effective in extracting nitrate than acetic acid. No significant difference occurred between water and the salt solution to extract nitrate from leaf tissue. Moreover, the result revealed that 0.01 M KCl extractant satisfies the recovery of ammonium from the leaves regardless of cultivar, fertilizer source, or amount of N application.

  PublisherDOI

• Physiology of medicinal and aromatic plants under drought stress

  The Crop Journal · 2024-01-14 · 74 citations

  articleOpen access

  Drought poses a significant challenge, restricting the productivity of medicinal and aromatic plants. The strain induced by drought can impede vital processes like respiration and photosynthesis, affecting various aspects of plants’ growth and metabolism. In response to this adversity, medicinal plants employ mechanisms such as morphological and structural adjustments, modulation of drought-resistant genes, and augmented synthesis of secondary metabolites and osmotic regulatory substances to alleviate the stress. Extreme water scarcity can lead to leaf wilting and may ultimately result in plant death. The cultivation and management of medicinal plants under stress conditions often differ from those of other crops. This is because the main goal with medicinal plants is not only to increase the yield of the above-ground parts but also to enhance the production of active ingredients such as essential oils. To elucidate these mechanisms of drought resistance in medicinal and aromatic plants, the current review provides a summary of recent literature encompassing studies on the morphology, physiology, and biochemistry of medicinal and aromatic plants under drought conditions.

  PublisherDOI

• Review on Physiological and Phytochemical Responses of Medicinal Plants to Salinity Stress

  Communications in Soil Science and Plant Analysis · 2023-06-27 · 16 citations

  articleCorresponding

  Salinity is one of the most severe abiotic stresses that affects plant growth in many parts of the world. One of the major stresses that limits the growth and yield of crops is considered by affecting several important plant mechanisms such as water relations, photosynthesis, and enzyme activity and may impart specific ion toxicities to plants. Plants under stress of salinity produce of a variety of reactive oxygen species that cause oxidative damage to lipids, proteins, and nucleic acids. Various antioxidant compounds in plants sweep reactive oxygen species and include ascorbate, glutathione, alpha tocopherol, carotenoids, and antioxidant enzymes including superoxide dismutase, catalase, and peroxidase. Due to the effect of salinity stress in medicinal plants, the concentration of essential oil in most medicinal plants increases. The physiology of plant response to salinity and its relationship with salinity resistance in different plants has been studied. Nevertheless, there are no comprehensive studies or thorough review of salinity stress in medicinal and aromatic plants. Thus, the current review was conducted to discuss the formation of secondary metabolites and physiological responses in these plants under salinity stress.

  PublisherDOI

• Book Review

  HortScience · 2023-07-28

  articleOpen access1st authorCorresponding
  PublisherOA PDFDOI

• Book Review

  HortScience · 2022-03-30

  articleOpen access1st authorCorresponding

  Soil Nitrogen Uses and Environmental Impacts. 2018, 2021. Rattan Lal and B. A. Stewart, editors. CRC Press, Boca Raton, Florida. 379 p. $43 paperback, $152 hardback. ISBN 9781032095653.The book has fifteen chapters covering the topics in the global nitrogen cycle, the use of nitrogen-containing fertilizers, and the effects of fertilizer use on the environment of the World. Each chapter is an independent one, and the text is not divided into sections of related topics. The chapters cover general topics of management of nitrogen in soil and specific topics in management of nitrogen in geographic regions of the World.

  PublisherOA PDFDOI

• Tuber Yield and Physiological Characteristics of Potato Under Irrigation and Fertilizer Application

  Communications in Soil Science and Plant Analysis · 2022-03-04 · 8 citations

  articleSenior authorCorresponding

  The effects of water availability in the soil and fertilizer application often strongly affect crop growth. Tuber dry matter yield and physiological characteristics of potato (Solanum tuberosum L.) were investigated under different irrigation regimes (S1, full irrigation, 100% of water requirement; S2, 75% of water requirement; and S3, 50% of water requirement). Nitrogen treatments were four amounts of urea (N1, providing 100% of N requirement; N2, 66% of N requirement; and N3, 33% of N requirement, and N4, 0 kg N/ha. Drought stress with 50% of the water requirement and limiting nitrogen fertilizer application suppressed the number and weights of tubers per plant. The yield of marketable tubers in S1 and S2 treatments was not significantly different. Treatments N1, N2, and N3 increased the yield of marketable tubers by 37, 33 and 12%, respectively, compared to N4. Drought stress (S3) increased the percentage of dry matter, but nitrogen fertilization did not cause a significant change. Drought stress (S3) increased the amount of soluble sugars in tubers and proline in leaves; however, the amounts of soluble sugars and proline were unchanged by increased nitrogen fertilization. Full irrigation and meeting of nitrogen requirements of potatoes led to high chlorophyll concentrations in leaves. Under drought stress (S3) and increasing nitrogen, the starch content of tubers was suppressed. The amount of nitrate in the tubers was not affected by irrigation treatments, but was raised by increasing nitrogen fertilization. Irrigation of 75% or more combined with fertilizer application of 66%, was an appropriate treatment for potato production.

  PublisherDOI

• Tillage

  2021-02-19

  book-chapter1st authorCorresponding
  PublisherDOI

Frequent coauthors

• Masoud Hashemi

  University of Massachusetts Amherst

  19 shared

• Donald N. Maynard

  University of Florida

  18 shared

• John E. Preece

  National Clonal Germplasm Repository

  17 shared

• M Leron Robbins

  16 shared

• Erik Ervin

  Clover Seed (China)

  16 shared

• Irrigation Charles

  American Society for Horticultural Science

  16 shared

• Carol J. Lovatt

  University of California, Riverside

  16 shared

• Anand Yadav Vegetables

  Clover Seed (China)

  16 shared

Awards & honors

• Environmental Quality Research Award, 1975
• Marion Meadows Award, 1977, American Society for Horticultur…
• Outstanding Teacher, Food and Natural Resources, 1992-1993
• Outstanding Professor, Stockbridge School of Agriculture, 19…
• Hewlitt Fellow, University of Massachusetts, 2000