Biostimulants in Agriculture—2nd Edition

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 present because of their nutrient content but due to their regulatory effects on a plant’s metabolism. Furthmore, 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 is waste streams, positioning these products in the spotlight for agricultural innovations aimed at achieving a circular economy.

The market of plant biostimulants has been growing rapidly. The use of plant biostimulants has allowed the concept of ecological intensification to be developed. Further, there is an awareness that agricultural productivity cannot decrease in the face of the need to feed a world population that continues to grow; instead, productivity 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. Specifically, science has focused on the need to elucidate their 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 positive publicity generated from scientific research and the advertising of the companies that have put them on the market. However, there is a lack of the detailed data necessary to allow farmers to use these products 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 focused on end users (farmers) to guide them in making decisions about production factors entailing costs they have to bear. Field, greenhouse or hydroponic experiments are preferred, with conditions as close as possible to those used by farmers; this 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 Rodrigues
Dr. Paolo Carletti
Dr. Domenico Ronga
Topic Editors