THE world under our feet is critical to the success of a crop, says agricultural ecologist David Hardwick.
Without a balanced and well-supported ecosystem within the soil, crops can’t get the nutrients they need, regardless of how much fertiliser is provided.
“The world under our feet is amazing, even though we don’t spend much time thinking about it,” said Mr Hardwick, who presented a talk at the recent Mudgee Small Farm Field Days.
He encouraged farmers to focus on their soil as it should be considered one of the most important assets on the farm.
“For agriculture groups and farmers, after people on the land, it’s the second most important asset we have.
“Soil sustains us and it sustains the farm business.”
The organisms that live within the soil are responsible for the ability of plants to take up nutrients, and the cycle of nutrients within the soil.
They can also help fight soil compaction and bring health back to the soil, he said.
The key to sustaining good soil biology was ensuring it was fed what it needed – a range of organic matter that could include various animal manures, straw, compost, and fertiliser.
“You need a mixture of green, brown and black compost,” Mr Hardwick said.
Brown compost was the most stable, while green was absorbed the quickest.
“If the living part of the soil is right then it’s important to think about how much horse manure do I need to put out each year?
“It’s just as important as the chemistry like fertilisers.
“If you feed soil organic matter, it’ll cycle nutrients and feed you.”
Mr Hardwick said soil microbes were responsible for the amount of phosphorous and nitrogen getting to plants.
“The more life in the soil, then the more chemical fertiliser or natural minerals in the soil available to the plant, especially in growing crops,” he said.
Healthy soil also helped save water.
“The healthier the soil, the more water that gets in and roots of the plants get bigger and so they need less irrigation,” he said.
“You also get less wilting in a crop.
“You can use 30 to 40 per cent less water.”
Mr Hardwick said plants needed a physical connection to the soil to let water in and allow them to grow.
“If you have erosion on your property then too much water is running off, rather than soaking into the ground.”
This could relate back to the biological condition of the soil, he said.
Mr Hardwick said the larger organisms were really important, as they cycled nutrients within the soil.
“You need them to make nutrients available to plants,” he said.
Without them, fertiliser wouldn’t be taken up by the crop.
Nematodes were often associated with pests in the soil, Mr Hardwick said, but actually could be beneficial and were important to the nutrient cycle.
Insects, mites and potworms, and many other creatures fell under the category of mesofauna and ate smaller creatures in the soil.
“They breakdown organic matter and cycle nutrients,” he said.
Earthworms in particular were important to the soil, as they could break through compacted soil, he said.
“They carry bacteria, they move it around and the worm castings are a nutrient which is a stimulate for plant growth,” Mr Hardwick said.
A good way to tell the condition of soil was to look at the roots of a plant.
The root system should have lumps of soil attached to it, he said.
It should also have a good volume of topsoil diversity – including tap and fibrous roots, and good soil-root contact.
He said getting good root depth in modern day agricultural crops was a struggle.
“You want roots going down a couple of metres, as the deeper it goes the more water it gets and the more organic matter.
“For example, sugarcane roots should go down about a metre, but with modern day agricultural systems you are lucky to get them 30 centimetres, so the plants are struggling all the time.
“It’s hard with 30-tonne trucks compacting soil.”