Inoculants for Seeds, Soil, and Plants
In agriculture, inoculants are microbial products containing beneficial microorganisms, such as bacteria and fungi, that are applied to seeds, soil, or plants to enhance crop productivity and health. They work by forming symbiotic relationships with plants to improve soil fertility, nutrient availability, and plant growth, while also helping to protect against pests and diseases. Inoculants can help reduce the need for chemical fertilizers and pesticides, making them an environmentally friendly tool for sustainable agriculture.
How inoculants work
- Nitrogen fixation: Certain inoculants, like Rhizobium bacteria for legumes, form nodules on plant roots and convert atmospheric nitrogen into a usable form for the plant.
- Nutrient delivery: Some inoculants help make other essential nutrients more available to the plant.
- Growth promotion: Certain microbes can stimulate plant hormone production, promoting overall growth.
- Disease suppression: Inoculants can induce systemic acquired resistance (SAR) in plants, making them more resistant to pathogens.
- Soil improvement: They can help improve soil structure and health by interacting with the existing soil microbiome.
Common types of inoculants
- Bacteria: Includes Rhizobium for nitrogen fixation and other beneficial bacteria like Bacillus and Pseudomonas.
- Fungi: Includes mycorrhizae and other beneficial fungi like Trichoderma.
- Archaea: Research is increasingly exploring the use of archaea for promoting plant growth.
Application and use
- Application methods: Inoculants can be applied as a seed treatment, mixed into the soil, or applied in-furrow with the seed at planting.
- Timing: Annual inoculation is crucial for maximizing benefits, especially for nitrogen-fixing crops.
- Sustainability: By using inoculants, growers can potentially reduce their reliance on synthetic fertilizers and pesticides, leading to more sustainable practices and improved human and environmental health.
(From AI Overview by Google)
Bacterial Inoculants
Nitrogen-Fixing Bacteria (Rhizobacteria)
Rhizobacteria live in root nodes, and are associated with legumes. The most commonly applied rhizobacteria are Rhizobium and closely related genera. Rhizobium are nitrogen-fixing bacteria that form symbiotic associations within nodules on the roots of legumes. This increases host nitrogen nutrition and is important to the cultivation of soybeans, chickpeas and many other leguminous crops.
For non-leguminous crops, Azospirillum has been demonstrated to be beneficial in some cases for nitrogen fixation and plant nutrition.
For cereal crops, diazotrophic rhizobacteria have increased plant growth, grain yield, nitrogen and phosphorus uptake under higher pH conditions in soil, and nitrogen, phosphorus and potassium content.
Phosphate-solubilising bacteria
To improve phosphorus nutrition, the use of phosphate-solubilising bacteria (PSB) such as Agrobacterium radiobacter has also received attention. As the name suggests, PSB are free-living bacteria that break down inorganic soil phosphates to simpler forms that enable uptake by plants.
Fungal Inoculants*
Symbiotic relationships between fungi and plant roots is referred to as a Mycorrhiza association. This symbiotic relationships is present in nearly all land plants and give both the plant and fungi advantages to survival. The plant can give upwards of 5-30% of its energy production to the fungi in exchange for increasing the root absorptive area with hyphae which gives the plant access to nutrients it would otherwise not be able to attain. The two most common mycorrhizae are arbuscular mycorrhizae and ectomycorrhizae. Ectomycorrhizae associations are most commonly found in woody-species, and have less implications for agricultural systems.
Arbuscular Mycorrhiza
Arbuscular mycorrhiza (AM) has received attention as a potential agriculture amendment for its ability to access and provide the host plant phosphorus. Under a reduced fertilization greenhouse system that was inoculated with a mixture of AM fungi and rhizobacteria, tomato yields that were given from 100% fertility were attained at 70% fertility. This 30% reduction in fertilizer application can aid in the reduction of nutrient pollution, and help prolong finite mineral resources such as phosphorus (Peak phosphorus). Other effects include increases in salinity tolerance, drought tolerance, and resistance to trace metal toxicity.
Fungal Partners
Fungal inoculation alone can benefit host plants. Inoculation paired with other amendments can further improve conditions. Arbuscular mycorrhizal inoculation combined with compost is a common household amendment for personal gardens, agriculture, and nurseries. It has been observed that this pairing can also promote microbial functions in soils that have been affected by mining.
Certain fungal partners do best in specific ecotones or with certain crops.
Some examples:
- arbuscular mycorrhizal inoculation paired with plant growth promoting bacteria resulted in a higher yield and quicker maturation in upland rice paddys.
- Maize growth improved after an amendment of arbuscular mycorrhizae and biochar. This amendment can also decrease cadmium uptake by crops.
Composite Inoculants
The combination of strains of Plant Growth Promoting Rhizobacteria (PGPR) has been shown to benefit rice and barley. The main benefit from dual inoculation is increased plant nutrient uptake from both soil and fertilizer. Multiple strains of inoculant have also been demonstrated to increase total nitrogenase activity compared to single strains of inoculants, even when only one strain is diazotrophic.
PGPR and arbuscular mycorrhizae in combination can be useful in increasing wheat growth in nutrient poor soil and improving nitrogen-extraction from fertilised soils.
Inoculants for Silage
Inoculants help improve the fermentation process, preserving silage quality — for example, the dry matter and protein content — for longer. They can also help with silaging at higher moisture. Furthermore, inoculants help to reduce the cost of supplementary rations.