Perhaps you should try some spelling variations:
irrigation schemes » irrigation scheme, irrigation systems
low conservation » local conservation, power conservation, soil conservation
case irrigation » scale irrigation, change irrigation, canal irrigation
supply case » supply cost, supply chain, supply curve
supply low » supply how, supply crowd

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( supply case irrigation schemes. ) or ( supply low conservation efforts. ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( supply case irrigation schemes. ) OR ( supply low conservation efforts. )).
• Adding a wildcard symbol may retrieve word variants: (( supply case irrigation schemes. ) or ( supply low conservation efforts. ))*.