Meta-analysis of crop yields of full, deficit, and partial root-zone drying irrigation

Techniques that reduce the volume of water applied in irrigation are desirable in the face of dwindling water resources and increasing demand for food. Various water-saving irrigation strategies, involving, the application of water below full crop-water requirements, have been advanced. This study employed meta-analysis to examine the relative crop yield performance of full irrigation (FI), deficit irrigation (DI) and partial root-zone drying irrigation (PRDI). The review included 35 studies, representing 14 study countries, and reporting 43 crop yields of (i) DI against that of PRDI; (ii) FI against that of DI; and (iii) FI against that of PRDI. Overall, crops under DI produces similar yields as PRDI but yields under both are typically lower than yields of FI. There were variations in yield response of different crops to DI and PRDI, suggesting crop and/or context-specificity. The main factors contributing to the yield response were crop species and soil texture. Crop yields between FI, DI and PRDI vary significantly if crops are more frequently irrigated. It is concluded that DI and PRDI result in yields lower than those of FI but yields of DI and PRDI are comparable. Economically justifying and weighing the cost of water-saving irrigation strategies against the expected yield penalties is therefore crucial.