Impact of irrigation scheduling on yield and water use efficiency of apples, peaches, and sweet cherries: A global meta-analysis

Efficient water use and irrigation water conservation with yield optimization are crucial for attaining water security in sustainable agriculture to fulfill the growing food demand of the overwhelming population. Meta-analyses were employed to assess the irrigation scheduling impact on fruit yield (Y), quality, and water use efficiency (WUE) of apples, peaches, and sweet cherries. The irrigation scheduling included were Moderate Deficit Irrigation (MDI; > 50 % ET and/or 50 % of the full irrigation (FI, 100 % ET or control)), Severe Deficit Irrigation (SDI;< 50 % irrigation or greater than 50 % reduction from FI), Regulated Deficit Irrigation (RDI: as stated in the experiments), Partial Rootzone Drying Irrigation (PRDI), Farmer Practiced Irrigation (FPI) and over-irrigation (OI). Treatments were compared with FI (100 % ET) or control with no water deficit. These treatments were analyzed across different moderators such as climate, soil, and cultivar. Meta-analysis indicated that irrigation scheduling across all treatments led to change in Y and WUE for in apple (Y = -15 % and WUE = 12 %), peach (Y = -13 % and WUE = 10 %), and sweet cherry (Y = 1 % and WUE = 14 %) Apple was affected the most by MDI (Y = -23 % and WUE = -15 %), SDI (Y = -25 %), RDI (Y = -10 % and WUE = 50 %), and OI (WUE = 25 %) followed by peach across MDI (Y = -14 % and WUE = 23 %), SDI (Y = -19 % and WUE = 5 %), RDI (Y = 18 % and WUE = 30 %), OI/FPI (Y= -11 %) while non-significant influence of SDI, MDI, RDI and PRDI on yield but improvement in WUE 14 %, 42 % and 50 % for SDI, MDI and RDI of sweet cherry was observed. Both OI and FPI influenced sweet cherry (Y = -10 % and WUE = -14 %). Across the climates, yield and WUE were affected more in arid climates followed by semi-arid, semi-humid, and humid climates. Across different soil types, the impact of irrigation scheduling differed significantly for crops in sandy soil followed by silt, clay, and loam soils. For example, in arid and semi-arid regions, increasing deficit irrigation (less water available) resulted in yield reduction and a decline in WUE for apples, followed by peaches. Yield reduction risk was smaller with higher WUE in finer-textured soil than the coarse-textured soil under deficit irrigation. Thus, irrigation scheduling effectiveness and yield reduction, along with WUE, can be optimized by consideration of deficit degree, climate, soil, species, and cultivar. and particularly plant hydraulic regulation behavior. Yield and WUE were highest for regulated deficit irrigation (RDI) in apple, peach, and sweet cherry. Our analysis suggests that RDI should be used to optimize yield and improve WUE under prevailing water scarcity.