USING microbiology can help you get the most out of your soil, by supplying information that can aid with fertiliser decisions.
This topic was the focus of a recent day run by the Strathalbyn Natural Resource Centre and held at Peats Soil and Garden Supplies at Brinkley.
Microbiology Laboratories soil scientist Ash Martin said microbes had a key role in the soil. By understanding more about soil through microbiology key issues can be overcome.
“It’s difficult to manage what you can’t measure,” he said.
“Microbes are like micro animals living in the soil. They’re everywhere but they’re most prevalent in the rhizosphere or root zone.”
Plant residues were food for microbes and, in turn, microbial respiration increased crop growth.
“Low carbon dioxide is often a limiting factor for maximum crop growth,” he said.
“Microbial activity produces carbon dioxide, so more microbial activity equals more carbon dioxide and more carbon dioxide equals more growth.
“If all the other things that go into growing a crop are being met, including adequate water, having extra carbon dioxide increases growth.”
Dr Martin said microbiology helps in a range of ways.
“Microbiology helps so that rather than go through boom and bust cycles, things tend to be more even and there’s less incidence of pests and diseases, more reliable yields and improved soil structure,” he said.
“You can also increase nutrient availability and release nutrients locked up in the soil, particularly in alkaline soils and suppress diseases.”
Dr Martin said how many microbes were in the soil depended on how much food was there for them to eat.
The make-up of microbes in the soil is influenced by their food sources, such as simple versus complex carbohydrates.
It is also influenced by environmental factors such as soil pH, moisture-holding capacity and mineral nutrient availability.
Bacteria play an important role in soil nutrient cycles, along with other microbes.
“You don’t want denitrifying bacteria, if you’ve got them in your soil and the soil is compacted, then you’ll be losing nitrogen,” he said.
“The more nitrogen you put on, the less work bacteria have to do.”
Moulds expand to find food sources, but their growth is limited in dry conditions.
“The types of food available and the environment have the most impact on the type of microbes you’re going to get,” he said.
“So, if you’re thinking about managing them, it’s an important thing to keep in mind.”
Sandy soils often lack structure, which reduces water infiltration, water holding capacity and beneficial microbial communities that drive important soil processes, such as nutrient release, disease resistance and carbon accumulation.
Water repellent soils in agriculture are usually caused by a build-up of waxy materials and incompletely processed organic matter in the surface layers. Natural waxes on the surface of plant leaves are the major contributor to this problem. Inadequately broken-down organic matter can also contribute, along with soil management practices that damage structure.
“Microbiology can offer balance, improved soil structure and suppress disease,” Dr Martin said.
“It offers well-structured soil that stores moisture, air and nutrients.
“In poorly structured soil water remains near the surface and water and nutrients move very slowly down the profile.”
Compost offers a top source of organic matter.
“Crusting can be caused by a number of things such as not enough organic matter in the soil and a lot of fertiliser,” he said.
“Compost is one of the best inputs you can give to soil.”
* Details: ciaaf.com.au
