The rhizosphere, a microzone where the root system interacts with the soil, plays a vital role in the nutrient availability for plants. Its nutrient effectiveness directly impacts the absorption and utilization of nutrients by plants. Plant rhizosphere nutrient management is a key aspect in optimizing the growth environment, enhancing their yield and quality.
Rhizosphere: The "Second Genome" of Plants
According to the World Population Prospect Report, the world’s total population is expected to increase to 8.5 billion by 2030 and rise to 9.7 billion by 2050. At that time, the food demand will be 70% more than it is now. Meanwhile, issues such as frequent extreme weather, degradation of arable land resources, and overuse of chemical pesticides pose unprecedented challenges to agricultural production. The rhizosphere, a dynamic interface between plant roots and soil, is known as the “second genome” of plants. Here, more than one billion microorganisms are active in each gram of soil, forming a complex rhizosphere microbiome. They coexist and cooperate with plant roots, regulating nutrient absorption, enhancing stress resistance, and even being able to “warn” of external stresses. The rhizosphere is like the “intelligent external brain” of plants. Microorganisms “talk” to the roots by secreting signaling molecules, helping plants retain water during drought, balance ions in saline-alkali soils, and activate immune defenses when diseases strike. This provides a new idea for dealing with climate change: rather than fighting against nature, it is better to harness the power of rhizosphere ecology.
Climate Change Forcing Technological Innovation
Beneath the plant ridges, an invisible “miniature battlefield” is quietly determining the future of global food security. Extreme weather has hit many parts of the world. The UK research institution Carbon Brief analyzed news reports related to extreme weather and crops from 2023 to 2024 and identified 100 cases globally where crops were damaged or destroyed due to high temperatures, droughts, wildfires, or other extreme events. In 2023, the United States experienced severe drought, leading to a significant reduction in the yields of corn and soybeans in the main grain-producing areas. In August 2023, floods and record-high temperatures caused a sharp decline in the pear yield in Italian orchards. Traditional plant protection solutions are becoming increasingly ineffective in the face of drastic climate changes.
Biostimulants are substances or microorganisms that, when applied to seeds, crops, or the rhizosphere, can stimulate the natural growth processes of plants, thereby enhancing or promoting nutrient absorption, fertilizer use efficiency, the tolerance of crops to abiotic stresses, or improving crop quality and yield. When biostimulants meet the rhizosphere, how do they reshape the rhizosphere nutrient cycle?
In plant rhizosphere nutrient management, biostimulants have become an important tool for achieving “reducing fertilizer use and increasing efficiency” and green and sustainable agriculture by regulating the rhizosphere microenvironment, activating soil microbial functions, and strengthening plant physiological responses. The combination of biostimulants and vegetable rhizosphere nutrient management essentially achieves the dual goals of efficient resource utilization and ecological security through the precise regulation of the interaction among “plants – microorganisms – soil”.
Microorganisms to The Rhizosphere
Microbial fertilizers enable microorganisms to grow and multiply in large numbers at the roots of crops. As dominant bacteria in the crop rhizosphere, they limit the reproduction opportunities of other pathogenic microorganisms. Arbuscular mycorrhizal fungi (AMF) directly enhance the absorption of essential nutrients such as nitrogen and phosphorus by plants, improve their resistance to biotic/abiotic stresses (such as drought and pathogens), and promote the colonization of nitrogen-fixing rhizobia and other plant growth-promoting rhizobacteria (PGPR) in the rhizosphere of host plants. Probiotic bacteria such as Bacillus subtilis produce lipopeptide antibiotics through metabolism, which can inhibit soil-borne pathogens such as Fusarium and reduce the incidence of rhizosphere diseases.
Humic Acid to The Rhizosphere
Humic acid can increase the activity of enzymes in plant roots, stimulate the elongation of plant roots and the increase of lateral root growth points, thereby increasing root vitality and the contact area between plant roots and soil nutrients, and enhancing the absorption of nutrients by plants. Humic acid combines with soil colloids to form water-stable aggregates, reducing nutrient leaching and improving the water and fertilizer retention capacity of the rhizosphere. Organic acids, including humic acid and fulvic acid, can inhibit the precipitation of phosphate minerals, improve the bioavailability of phosphorus, and increase the effectiveness of trace elements.
Amino Acids to The Rhizosphere
Amino acids, as metabolic precursors of plant hormones, can promote the absorption, assimilation, and transport of nitrogen nutrients by plants. At the same time, they can also increase the solubility of minerals, thereby enhancing the availability of minerals.
Seaweed Extracts to The Rhizosphere
The polysaccharides and phenolic substances in seaweed extracts can provide a carbon source for nitrogen-fixing bacteria and phosphorus-solubilizing bacteria in the rhizosphere, enhancing their metabolic activity. The chelating and hydrophilic properties of alginic acid active substances can improve the physical, chemical, and biological properties of the soil, increase soil biological vitality, promote the release of available nutrients, thereby improving the water retention capacity of the soil and promoting the growth of beneficial microorganisms in the rhizosphere.
Chitosan Oligosaccharides to The Rhizosphere
Chitosan-based biostimulants have an auxiliary effect in nematode control. Chitosan oligosaccharides can induce plant roots to secrete chitinase, which destroys the chitin in the cell walls of nematode eggs, improves the rhizosphere microbial population, inhibits nematodes, repairs damaged roots, and promotes root growth. Dora COS, Dora AOS