Effect of Supplemental Irrigation and No Tillage on Bread Wheat: A Global Meta-Analysis Approach

A global meta-analysis was conducted to assess how various abiotic factors influence grain yield (GY) and grain protein content (GPC) of bread wheat. For this purpose, forty peer-reviewed papers published between 1986 and 2024 were analyzed. The results showed that the application of supplemental irrigation had significant effects on GY and GPC depending on the climate. In a semi-arid climate, supplemental irrigation had a positive effect on the yield, increasing it by 1,154.08 kg ha^-1, and a negative effect on GPC, decreasing by 2.09%. However, in a sub-humid climate, a yield decrease of 499.25 kg ha^-1 was observed. In addition, GY and GPC responses to supplemental irrigation were significant according to soil textures (p<0.0001). When irrigation was applied, the highest GY increase was observed in coarse- and fine-textured soils (1,507.41 kg ha^-1 and 1,826.18 kg ha^-1, respectively). However, the medium-textured soils indicated negative responses (MD=-1,811.63 kg ha^-1). Indeed, the beneficial effect of supplemental irrigation on GPC was demonstrated in fine-textured soils (MD=0.91%). However, a negative response of irrigation was observed in coarse- (MD=-1.67%) and medium-textured (MD=-1.60%) soils. When no tillage was implemented, GY response was positive in both sub-humid and humid climates, leading to an increase by 1,660.41 kg ha^-1 and 1,650.02 kg ha^-1, respectively. In contrast, no tillage led to a decreased GY (by 499.25 kg ha^-1) in the semi-arid climate. Although no tillage had no significant impact on GPC alone, GY and GPC showed positive responses, leading to an increase by 201.36 kg ha ^-1 and 0.13% in coarse-textured soils and 1,390.57 kg ha^-1 and 1.11% in medium ones, respectively. However, a negative response to no tillage was observed in fine-textured soils (MD=-0.45%).