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Professor Ray R. Weil is an internationally recognized expert on soil science, nutrient cycling, soil organic matter and cover crop systems for soil health and water quality. His methods for soil microbial biomass and active Carbon are adopted by USDA/NRCS and researchers worldwide. His research on multi-purpose cover crops and ecological approaches to soil management is used by landscape managers and farms, large and small. He has advised on food security and soil management in Africa and other developing regions. He teaches undergraduate and graduate-level courses in soil science and sustainable agriculture. His textbook, The Nature and Properties of Soils, is the most widely used soils textbook in the US and around the world.

Environmental Science & Technology 0115 HJ Patterson Hall 4065 Campus Dr. College Park, Maryland 20742
For Package Delivery Dock H, AnSc-AgEng Bldg. #142 8127 Reagents Drive College Park, Maryland 20742


  • soil science
  • agronomy
  • soil health
  • sustainable agriculture
  • International Development
  • Cover Crops
  • soil fertility
  • soil organic matter
  • soil carbon
  • soil compaction
  • Soil Conservation

Research Focus

  • Multi-Purpose Cover Crops to Enhance The Environment and Farm Profitability
  • Soil Health & Quality Management for Sustainable Agriculture
  • Profitable and Soil-Health-Building Strategies for Transitioning to Organic Grains
  • Active Organic Matter Test to Help Assess Soil Health
  • Environmental Impacts of Management Intensive Grazing Based Dairy Farms
  • Sulfur Fertility to Enhance Yields and Protein Quality of Grain Legumes
  • Soil Management and Indigenous Nutrients for African Small Holder Farmers

Ray R. Weil is a leader in researching and promoting the adoption of more sustainable agricultural systems in both industrial and developing countries. His research focuses on organic matter management for enhanced soil quality and nutrient cycling for water quality and sustainability. Dr. Weil teaches five undergraduate and graduate courses. He has been a dedicated and effective educator for more than 25 years. He has taught over 5,500 undergraduate and graduate students in his university courses, addressed over 5000 farmers at meetings and field days, and helped train hundreds of researchers and managers in numerous companies and organizations. He has been the major advisor for 40 MS and PhD students. The undergraduate and graduate courses taught by Dr. Weil include two CORE courses, Soil and Environmental Quality (ENST105) and Fundamentals of Soil Science(ENST200), and three upper level courses: Principles of Soil Fertility(ENST411), Issues in Sustainable Agriculture(ENST441), and Advanced Soil-Plant Relationships(ENST711). Student evaluations always praise his engaging teaching style and enthusiasm for soil science, despite his reputation for maintaining high standards and rigorous grading. An early (1975) author on the subject of grade inflation, Dr. Weil has developed and practiced a system of grading that has held the line on grade inflation for over two decades.

Integration of Teaching and Research.   A hallmark of Dr. Weil’s program is the integration of his teaching and research programs so that each benefits from the other. Students are energized by hearing first hand accounts of soils problems and investigations and benefit by learning science from an active scientist. On the other hand, discussion of cutting-edge concepts in class often inspire Dr. Weil to work on new research ideas. The positive experience that students have in his classes is reflected by the fact that many of Dr. Weil’s graduate students took his courses when they were undergraduates. The synergism between Dr. Weil’s teaching and research, and his ecological approach to soil science are especially evident in his work that completely revised the most widely used textbook in the field, The Nature and Properties of Soils, which he coauthors with teh late Cornell Professor Emeritus, Nyle Brady. Dr. Weil uses an innovative, interactive teaching style to intellectually challenge students and emphasize fundamental concepts and an ecosystems approach. In teaching, he strives for the three “I”s: inspire, integrate and inform. He inspires students to delve into science and live a conscious and soils-literate life. He helps students use soil science to integrate into a coherent system, the tremendous array of isolated facts and basic principles to which they are exposed. And he informs students about new knowledge, new sources of knowledge, and new tools to create knowledge.

Scholarly Research Program. Dr. Weil’s research program combines three interrelated areas: 1) Organic Matter Management for Soil Quality; 2) Sustainable Cropping Systems; and 3) Soil Management for Improved Nutrient Cycling and Water Quality. His soil quality program has achieved international recognition for its innovative efforts to develop a soil quality index and methods for the rapid, routine assessment of soil quality indicators, including aggregation, active fraction organic carbon and soil microbial biomass. His research probes fundamental relationships between soil organic matter management and soil ecological functions. An early innovation of his was to borrow from aquatic ecology the concept C assimilation capacity. He has contributed to our understanding of the active fraction of soil organic matter and his lab and field methods for active carbon analysis are being used in many types of ecosystems around the world. He has been an active leader in Soil Organic Matter, Soil Health/Quality, and Soil Fertility in the Soil Science Society of America.

In addition to studying the effects of crop management on soil quality, Weil has worked to develop new cropping system practices with the potential to improve profitability and environmental impacts. He has investigated the inter-cropping of grain legumes with cereal crops both in the US and in developing countries, including pioneering work on the winged bean in tropical environments. He has studied nutrient utilization and weed suppression by such intercrops. He has twice been awarded a Fulbright Fellow to support his work in developing countries. His work on rainwater distribution in soils under ridge till and no till corn documented the importance of funnel flow to the crop row and has been useful in the work of soil-water modelers. He has also studied new cover crop systems to enhance soil quality and crop profitability. His lab demonstrated that tap-rooted cover crops create root channels through compacted subsoil layers during the winter that summer cash crop roots can follow to penetrate compacted subsoil during dry summers when soil strength is high. His pioneering research on the multiple benefits of a forage radish cover crop system has had major impacts throughout the states and many other countries. Dr. Weil’s research on nutrient cycling in agroecosystems has focused on nitrogen, phosphorus and sulfur. He has worked on the stratification of various forms of P under no-till management, the impact of manure applications on N losses to groundwater under irrigated coastal plain soils, the occurrence of sulfur deficiencies in Africa, the direct utilization of phosphate rocks. Currently his lab is investigating the water quality impacts of intensive rotational grazing on dairy farms, including the importance of dissolved organic forms in the leaching loss of both nitrogen and phosphorus.

Dr. Weil has been a leading figure promoting research on, and the practice of, sustainable agriculture in the US and abroad. In the 1980s, he helped the American Society of Agronomy define “sustainable agriculture”, the main component of this definition subsequently were adopted in the major US Congressional legislation (1990 farm bill) that gave birth to the main current research support program for sustainable agriculture in the USDA. He has helped develop farmer-oriented soil quality assessment tools, such as his innovative method of estimating active fraction soil C and a soil health scoring system. International Development Dr. Weil has worked on research and development programs in Africa, Asia and Central/South America since his start as a Peace Corps Volunteer in Ethiopia in 1970. He has conducted research, project development or evaluation in the field in Sri Lanka, Malawi, Zimbabwe, Tanzania, Ethiopia, Honduras, Burkino Faso and Brazil. He has worked as a consultant to the World Bank to educate its project and regional managers to recognize and plan for agricultural development in harmony with environmental values. In this role he helped lead eight workshops for the World Bank between 1997 and 2001. In 2001, he was funded by the World Bank to assist the Government of Ethiopia for a six-month sabbatical in integrated systems research and collaborations between the Ethiopian government and the CGIAR livestock center in Addis Ababa. In 2009, he spent a seven-month sabbatical working with the millennium villages project in seven countries in Africa diagnosing and solving agricultural problems in the field and advising the project and integrated agricultural develop and soils related issues. Since 2011 he has been developing and implementing the use of his SoilDoc system for field diagnosis of soil fertility problems.