Biostimulants in Agriculture

Dear Colleagues,

Plant biostimulants are substances or microorganisms applied to plants, soils or seeds with the aim of enhancing crop yield, quality traits, plant tolerance to a wide range of biotic and abiotic stresses and/or nutrient use efficiency. The beneficial effects of plant biostimulants are usually not due to their nutrient content but to regulatory effects on the plant’s metabolism. Biostimulants are known to elicit positive plant responses at lower doses than traditional fertilizers. Some of the substances with the greatest abundance and diversity in the markets are humic substances (humic and fulvic acids), free amino acids, seaweed extracts, inorganic compounds and beneficial microorganisms (fungi and bacteria). An important source of biostimulants are waste streams, which places these products in the spotlight for agricultural innovations directed toward achieving a circular economy.

The market of plant biostimulants has been rapidly growing. The use of plant biostimulants has allowed the concept of ecological intensification to be developed. There is an awareness that agricultural productivity cannot decrease in the face of the need to feed a world population that continues to grow but, instead, must be increased by improving nutrient use efficiency and reducing the use of conventional fertilizers and other external inputs.

Research on plant biostimulants is gaining increasing attention among scientists. The list of scientific publications and reviews on the subject to date is considerable. Science has focused on the need to elucidate the modes of action, namely their impact at the molecular, cellular and/or whole-plant level, taking into account the complexity of substances that are used as plant biostimulants.

Although science has been doing a remarkable job, the information available for farmers to make their decisions remains vastly insufficient. Producers are encouraged to use these plant biostimulants due to the general positive publicity that comes from the science and the advertising of the companies that have put them on the market. However, there is a lack of data with the necessary detail to allow farmers to be able to use them safely and with some guarantee that they will obtain a return on their investment. Thus, for this Special Issue we intend to select a set of studies oriented toward the end users (the farmers) that can guide them in making decisions about these production factors entailing a cost that they have to bear. Field, greenhouse or hydroponic experiments are preferred in which the conditions are as close as possible to those used by farmers, which may also include examining drought, salt, low temperature and/or other stress conditions. So long as the experimental conditions and consistency in the results are duly established, studies that show positive, nonsignificant or negative responses of plants to the application of plant biostimulants will be equally considered.

Prof. Dr. Manuel Ângelo Rosa Rodrigues
Prof. Dr. Carlos M. Correia
Dr. Paolo Carletti
Prof. Dr. Antonio Ferrante
Topic Editors