Perhaps you should try some spelling variations:
integration theories » integration theory, integration through, integration efforts
water integration » water integrating, factor integration, data integration
crop irrigation » drip irrigation, scale irrigation, canal irrigation
support crop » support crops, support group, support cross
systems. » 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 crop irrigation systems. ) or ( supply water integration theories. ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( support crop irrigation systems. ) OR ( supply water integration theories. )).
• Adding a wildcard symbol may retrieve word variants: (( support crop irrigation systems. ) or ( supply water integration theories. ))*.