Biostimulants and Their Role in Improving the Growth and Yield of Maize under Drought and Salinity Conditions: A Scientific Review

Abiotic stresses such as drought and salinity have been increasing as a limitation to maize (Zea mays L.) productivity because these abiotic stressors affect water relations, photosynthesis, ion homeostasis, nutrient acquisition, oxidative balance and ultimate yield development. Here, plant biostimulants have become a promising aspect of climate-resilient crop management since it can lead to increased tolerance to stress without being used as a mere conventional fertilizer. The current review critically evaluates recent findings of the role of biostimulants to enhance maize growth and yield during drought and salinity, focusing on microbial-based biostimulants, humic and fulvic compounds, seaweed- and algae-derived biostimulants, amino acid- and protein hydrolysate-based biostimulants, and chitosan-based bi The existing maize literature reveals that the most reliable advantages are related to enhanced root development, enhanced relative water status, stabilization of photosynthetic activity, enhanced antioxidant defense, osmotic adjustment, and under salinity, enhanced ion selectivity and rhizosphere activity. Microbial inoculants and humic/ulvic compounds and seaweed extracts demonstrate the highest level of maize-specific evidence, with amino acid/protein hydrolysate and nano-enabled methods showing promise but not as well validated under field stress. Although the positive responses were repeated, the review also indicates that the effectiveness of the treatment is genotype-dependent, stress-dependent, and time and formulation-dependent, in addition to being dependent on the interaction with soil conditions. Hence, biostimulants cannot be viewed as a universal yield enhancer; rather, they are a situational physiological aid that can aid nutrient and water management in maize. Future developments need enhanced standardization, increased multi-location field experiments and more explicit mechanistic connection of product composition and maize reaction to a single and combined set of abiotic stresses.