Maize Grain Yield and Quality Improvement Through Biostimulant Application: a Systematic Review

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Increasing the productivity of cereals such as maize while protecting the environment remains a fundamental impetus of healthy food production systems. The use of biostimulants is one of the sustainable strategies to achieve this balance, although the ability of biostimulants to enhance maize productivity varies. Moreover, research on the efficacy of biostimulants is ubiquitous with limited comprehensive global analysis. In this context, this systematic review evaluated the sole and interactive effects of biostimulants on the yield and quality of maize grain from a global perspective. Changes in yield (t ha-1), protein content (%), starch content (%) and oil content (%) of maize grain were assessed. Results revealed that sole and combined application of biostimulants significantly improved grain yield. Irrespective of the region, the highest and the lowest grain yields ranged between 16-20 t ha-1 and 1-5 t ha-1, respectively. In sole application, the promising biostimulants were chicken feather (16.5 t ha-1), and endophyte Colletotrichum tofieldiae (14.5 t ha-1). Sewage sludge × NPK (15.4 t ha-1), humic acid × control release urea (12.4 t ha-1), Azospirillum brasilense or Bradyrhizobium japonicum × maize hybrids (11.6 t ha- 1), and Rhizophagus intraradices × earthworms (10.0 t ha- 1) had higher yield for the interactive effects. The effects of biostimulants on grain quality were minimal, and all attributes improved in the range from 0.1 to 3.7%. Overall, biostimulants had a distinct improvement effect on yield, rather than on the quality of grain. As one way of maximising maize productivity, soil health, and the overall functioning of crop agroecosystems, the integrated application of synergistic microbial and non-microbial biostimulants could provide a viable option. However, the ability to produce consistent yield and quality of grain improvement remains a major concern.