Perhaps you should try some spelling variations:
"support drip irrigation schemes." » "support drip irrigation scheme.", "support drip irrigation systems.", "support deep irrigation schemes.", "support during irrigation schemes.", "support crops irrigation schemes."
"supply service irrigation system." » "supply service obligation system.", "supply surface irrigation system.", "supply service obligations system.", "supply service irrigation systems.", "supply service irrigation water.", "supply service irrigation scheme.", "supply services irrigation system."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("support drip irrigation schemes.") or ("supply service irrigation system."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("support drip irrigation schemes.") OR ("supply service irrigation system.")).
• Removing quotes may allow a broader search: (( support drip irrigation schemes. ) or ( supply service irrigation system. )).
• Adding a wildcard symbol may retrieve word variants: (("support drip irrigation schemes.") or ("supply service irrigation system."))*.