Improve The Diversity of Soil Microbes
Nature keeps plants healthy through diversity.
Why Diversity Matters
Diversity in soil microbial populations is pivotal for nutrient uptake and disease suppression. Soil microbes operate through multiple means, including developing symbiotic relationships with plant roots to protect the plant from disease; releasing nutrients from organic matter and stimulating plant growth; degrading pesticides and toxic substance; fixing atmospheric nitrogen and improving soil structure. The incidence and severity of root disease is an indirect assessment of soil health (Abawi 2000).
Why add microbes?
Soil microbial biomass and diversity has significantly declined with intensive agriculture which has negatively impacted on yield, disease & farm sustainability. The resultant decline in soil health is now a global issue. Intensive agriculture is at the crossroad and needs to find ways to improve microbial biomass and diversity to reduce disease.
Many activities in modern agriculture deplete soil microbes resulting in increased disease and reduced nutrient uptake.
- Annual broad-acre crops – microbes soon die once crops are harvested and they are without the presence of living roots.
- Vegetable production – soils are cultivated & fumigated, destroying roots and beneficial microbes.
- Orchards and vineyards – spraying weeds with herbicides causes plant roots and beneficial microbes to die
There is considerable research outlining this eg under field conditions in the frequent use of fungicides, herbicides and insecticides caused a decrease in bacterial-feeding, fungal-feeding, predatory and omnivorous nematodes and an increase in plant-parasitic nematodes(Geense et al 2015; Bailey 2003; Imfeld2012). In addition, agrochemicals have been shown to have a strong negative impact on soil enzyme activity (Moeskops 2010; Ratnadass 2012).
Microbial diversity works
Microbial diversity helps create disease suppressive soils
Soil microbes are the key to creating disease suppressive soils. They have a pivotal role in improving soil health and reducing disease.
Microbial diversity helps create disease suppressive soils
Disease suppression is related to:
- A global increase in soil microbial biomass. A large biomass creates a competitive environment deleterious for the pathogens ( Janvier 2007; Ratnadass 2012).
- Diversity and structure of microbial communities. A greater biodiversity (number of species present in the ecosystem) has long been synonymous with better soil quality, diversity being considered as a key component of soil stability and function (Janvier 2007). Suppressive soils consistently have higher populations of actinomycetes and bacteria than do soils conducive to diseases (Ratnadass 2012).
Functional characteristics of individual microbial species which are at least as important as the total diversity (Janvier 2007). - The total amount of microbiological activity at a time critical to the pathogen. In a sense, general suppression of a pathogen in soil is the equivalent of a high degree of soil fungistasis. Not a single microorganism or specific group of microorganisms is responsible by itself for general suppression (Janvier 2007).
- Good soil health and soil biota. Soil borne diseases are most damaging when soil conditions are poor as a result of inadequate drainage, poor soil structure, low organic matter, low soil fertility, and high soil compaction. The aforementioned cultural practices all have an impact on these physical characteristics as well as increasing the diversity of the soil biota. Implementation of these practices improves the soil health and reduces disease incidence in a sustainable manner (Abawi 2000; Bailey 2003).