Applying Biostimulants to Combat Water Deficit in Crop Plants: Research and Debate

Climate change has increased the severity of drought episodes by further reducing precipitation in vulnerable zones. Drought induces a substantial decrease in agricultural water, reducing crop yields. Consequently, addressing water consumption can increase farmers' profits. This work describes lab-to-field research in Zea mays, using two biostimulants: glycine betaine (GB) and L-pyroglutamic acid (PG). The biostimulant optimal dosages were selected using a hydroponic system with 20% polyethylene glycol and nursery experiments under water-deficit irrigation. The established dosages were evaluated in field trials in which irrigation was reduced by 20%. Laboratory biostimulant optimisation showed in stressed treated seedlings (GB 0.1 mM; PG 1 mM) an increased dry weight, relative growth rate and water use efficiency, reducing seedling growth loss between 65 and 85%, respectively. Field trials using a GB-optimised dosage showed an increase in plants' growth, grain yield and flour Ca content. In addition, grain flour carbohydrate content and protein remained similar to control well-watered plants. Finally, the economic aspects of biostimulant treatments, water consumption, water sources (ground vs. desalinated) and grain biomass were addressed. Overall, GB treatment demonstrated to be a valuable tool to reduce water consumption and improve farmers' earnings.