Perhaps you should try some spelling variations:
"support grid irrigation systems." » "support grain irrigation systems.", "support drip irrigation systems.", "support gray irrigation systems.", "support agri irrigation systems.", "support grant irrigation systems.", "support group irrigation systems.", "support grid irrigation system."
"support crop irrigation systems." » "support drip irrigation systems.", "support scale irrigation systems.", "support canal irrigation systems.", "support crops irrigation systems.", "support cross irrigation systems.", "support across irrigation systems.", "support crop irrigation system."

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (("support grid irrigation systems.") OR ("support crop irrigation systems."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"support grid irrigation systems.\") OR (\"support crop irrigation systems.\"))".
• Removing quotes may allow a broader search: (( support grid irrigation systems. ) OR ( support crop irrigation systems. )).
• Adding a wildcard symbol may retrieve word variants: (("support grid irrigation systems.") OR ("support crop irrigation systems."))*.