Organic amendments optimize Triticum aestivum var Zincol-16 performance under water stress through enhancement in physio biochemical traits, secondary metabolites and yield.

Declining soil fertility due to unstable cultivation practices is a major challenge, particularly under water-limited conditions, leading to reduced crop productivity. Identifying sustainable soil amendments that enhance plant resilience and improve soil properties is crucial for ensuring food security in arid and semi-arid regions. Among these, activated acacia biochar has shown potential in improving soil quality. A pot-scale experiment was conducted to evaluate the effects of four different soil amendments i.e., biochar amended soil (BAS), vermicompost amended soil (VCAS), perlite amended soil (PAS), activated biochar amended soil (ABAS) on wheat physiology and yield under moisture stress conditions. Soil amendments were incorporated at 2.5% and 5% (dry weight basis) by through mixing. Two water regimes were applied from booting to grain filling: (i) optimal moisture (80% of field capacity, FC) (ii) moisture stress (50% of FC). The highest improvement in water holding capacity was observed in soil amended with 5% ABAS which increased by 39.31% (16.3 ± 0.72) compared to non-amended soil (NAS). Under 50% FC, plants grown in 2.5% and 5% ABAS exhibited significantly higher total chlorophyll content (11%), stomatal area (42%), stomatal aperture (29%), and guard cell area (44%) than NAS. The maximum increase in photosynthetic rate (threefold and 4.2-fold higher) and transpiration rates (threefold and 3.2-fold higher) were observed in plants of 2.5% BAS and 5% ABAS, respectively than NAS. However, the highest improvement in water use efficiency (52%) was observed in the plants of 2.5% ABAS than NAS. Leaf nutrient assessment showed a 10.4% and 7.6-fold increase in percent weight of carbon and phosphorus in the plants of BAS, 75% higher sodium in PAS, 139% higher calcium in VCAS, and 97.5% higher nitrogen and 58% higher magnesium in ABAS than NAS. Additionally, the highest accumulation of metabolites including amides, polysaccharides, lignin and waxes, was recorded in plants grown in amended soil, particularly in ABAS. Regarding yield attributes, plants grown in 2.5% and 5% ABAS had significantly (p < 0.05) higher leaf area (84-85%), spike length (89-93%), spikelet per spike (139-166%), and 1000 grain weight (133-157%) under 50% FC compared to NAS. In conclusion, activated biochar considerably enhances plant physio-biochemical attributes and yield under water stress conditions. Its applications may be recommended for farmers in arid regions to mitigate the adverse effects of water scarcity.