Modern agriculture is revealing an ever-increasing interest for Biostimulants, once considered substances promoting plant growth without being nutrients, soil improvers, or pesticides.
The history of biostimulants refers to two prominent figures: Zhang and Schmidt from the Department of Crop and Soil Environmental Sciences of the Virginia Polytechnic Institute and State University. They were the first ones in 1997 to suggest the term “biostimulant“, indicating all the materials that, in minute quantities, promote plant growth. At first, they were humic acids and seaweed extracts.
During the last decade there have been stated many definitions of biostimulants following the different Decree-Laws, until 2013, with the definition of European Biostimulants Industry Council’ (EBIC), which described biostimulants as: Plant biostimulants contain substance(s) and/or micro-organisms whose function when applied to plants or the rhizosphere is to stimulate natural processes to enhance/benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, and crop quality. Biostimulants don’t directly act on parasites and pathogens and therefore they are not covered by pesticides’ category “.
The characteristics of biostimulants
Many types of materials and substances fall within the category of biostimulants, all with common features, such as:
- Different modes of action;
- Increase in nutrient use efficiency;
- Increased tolerance to stress;
- Chemical, biochemical, physiological and hormonal effects;
- Increase in nutrients absorption, reducing the quantity of fertilizers used;
- Increase in yields and products quality.
How to use them.
There is evidence that biostimulants have positive effects on crops, so they have become some widely used products. Anyway it’s necessary pointing out that these substances can’t replace a correct nutrition and water-mineral management of the crops.
The correct use of biostimulants is based on the awareness that we have to look at them as complementary products to nutrients, as well as a support in agriculture, especially with difficult situations raising also from an optimal crop management.
Seaweed extracts.
Among the first and most well-known biostimulant substances there are seaweed extracts, always used as fertilizers to improve soil fertility. Depending on seaweed kinds, harvesting period and extraction process, we can get different resulting products in terms of chemical and biostimulant properties.
Their use helps improving sprouting speed, plant growth, fruit setting, yields, quality of crops and resistance against stress such as drought, extreme temperatures and soil salinity.
Humic substances.
Some different biostimulant substances of complex organic macromolecules,
resulting from both the decomposition of organic matter and the activity of microorganisms.
These substances can stimulate the rhizogenesis and the absorption of nitric nitrogen, with a consequent improvement in the absorption and assimilation of inorganic nitrogen by the crop.
Protein hydrolysates.
The list of biostimulating substances is completed by protein hydrolysates, containing a mixture of amino acids and soluble peptides, obtained by chemical and enzymatic hydrolysis from agroindustrial by-products, from both plant sources (crop residues) and animal wastes (e.g. col-lagen, epithelial tissues).
Such biostimulant substances improve the absorption and assimilation of nutrients, making the plant more resistant to environmental stress, with a consequent higher quality of final products.
The makings and dosage of biostimulants.
By increasing the absorption and assimilation of nutrients as well as the resistance to stress and yields quality, biostimulants are a great opportunity for modern agriculture and its sustainability.
However, the agricultural efficiency will depend on several factors:
- right dosage of biostimulants, according to the kind of crop;
- application modes based on environmental and technological features;
- use of biostimulants as support to an agriculture with a proper water-mineral management of the crops.
