The National Agricultural Library houses one of the world's largest (if not THE largest) collections of historic and current resources focused on agriculture and related subjects.
NAL resources accessed through dropdown menus under: Topics, Research Tools, Collections, Data, and Services are amazing and well worth exploring! Program Areas, under "About Us" should also not be missed.
The NAL Thesaurus is also extremely useful.
Using the search box on the main NAL page will yield results from the USDA. There is some overlap with what you will find in PubAg,
There is more than one approach to effectively using NAL. Two examples:
AGRICOLA is the catalog for the National Agricultural Library's holdings. It includes citations to journal articles, with abstracts; and also citations to for monographs, serials, audiovisual materials and online content from around the world. AGRICOLA includes but is not limited to resources available in the National Agricultural library. The database contains more than 5,000,000 records/citations and includes records for works from as far back as the 15th century.
You can search for citations to books OR to journal articles OR search for both books and journal articles together.
AGRICOLA encompasses all aspects of agriculture and related disciplines, including animal and veterinary sciences, entomology, plant sciences, forestry, aquaculture and fisheries, farming and farming systems, agricultural economics, extension and education, food and human nutrition, and earth and environmental sciences.
There is some overlap with PubAg although each uses a different search interface and AGRICOLA includes relevant items that are not peer-reviewed journal articles.
The AGRICOLA Help page is informative and helpful.
PubAg provides full-text documents published by the USDA and also citations to peer-reviewed agriculture-related articles, with links for full-text access when available. PubAg includes resources back to 2000.
A search in All Fields for "climate change" (on 1/20/22) yielded 72,663 results, Clicking on the Text Availability filter reveals that 69,186 are citations and 3,477 are full text. Additional filters: Subject, Journal Title, Year.
Searching is also possible by Author, Title, Subject, or Journal.
There is some overlap with AGRICOLA although each uses a different search interface.
The PubAg FAQ page is informative and helpful.