Searching in a library catalog requires looking for broader topics such as soil amendment rather than the more specific biochar soil amendment for semi-arid regions.
LIBRARY OF CONGRESS CLASSIFICATION OUTLINE (United States Classification system)
CLASS S - AGRICULTURE
S subclass Agriculture (General)
SB subclass Plant culture
SD subclass Forestry
SF subclass Animal culture
SH subclass Aquaculture. Fisheries. Angling
SK subclass Hunting sports
Please note that Food Science resources are located in the TX subclass area; Nutrition resources are also found in the TX and QP subclasses; and Viticulture/Winemaking resources are located in the TP subclass area.
Below are large-scale open-access book collections freely available to researchers world-wide
Your academic/research institution outside of the United States may have access to some of these publisher collections which must be licensed in order to receive access. See the ebooks page from the Agriculture & Related Fields Subject Guide.