Marschner Review

Plant and Soil

, Volume 383, Issue 1, pp 3-41

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Agricultural uses of plant biostimulants

  • Pamela CalvoAffiliated withDepartment of Entomology and Plant Pathology, Auburn University
  • , Louise NelsonAffiliated withDepartment of Biology, University of British Columbia
  • , Joseph W. KloepperAffiliated withDepartment of Entomology and Plant Pathology, Auburn University Email author 



Plant biostimulants are diverse substances and microorganisms used to enhance plant growth. The global market for biostimulants is projected to increase 12 % per year and reach over $2,200 million by 2018. Despite the growing use of biostimulants in agriculture, many in the scientific community consider biostimulants to be lacking peer-reviewed scientific evaluation.


This article describes the emerging definitions of biostimulants and reviews the literature on five categories of biostimulants: i. microbial inoculants, ii. humic acids, iii. fulvic acids, iv. protein hydrolysates and amino acids, and v. seaweed extracts.


The large number of publications cited for each category of biostimulants demonstrates that there is growing scientific evidence supporting the use of biostimulants as agricultural inputs on diverse plant species. The cited literature also reveals some commonalities in plant responses to different biostimulants, such as increased root growth, enhanced nutrient uptake, and stress tolerance.


Microbial inoculants Humic acid Fulvic acid Protein hydrolysates Amino acids Seaweed extracts Biostimulants