So what is soil health?
or Understanding and Managing Soil Biology
Soil health is a made up of its physical, chemical and living components, but can only be assessed by its living components, if the soil has no living components then it’s dirt. If the physical and chemical components are correctly balanced, but other factors stop the growth of life, then it is unlikely that soil could maintain a healthy status. New research has shown the critical importance of Soil health and organic carbon balance to soil health. Soil organic carbon is the main component of soil organic matter, or the broken-down remains of plant and animal life. So what is the connection between soil carbon, soil health and soil biology?
Here is the important bit
“Organic matter can not break down by itself!”
Decomposition is done by a vast army of shredders, fungal feeders, predators and herbivores that devour plant and animal matter whole, dissolve it with acids and enzymes, grind it to a paste, and suck its juices! This work is carried out beneath the surface of the soil by creatures that can number billions of organisms per gram of healthy soil, imagine one teaspoon of soil can containing up to 1 billion bacteria. That equals a mass of over two tonnes of livestock per hectare! No wonder some people talk of ‘micro herds’.
The challenge for modern farming
is to understand the needs of the ‘micro herds’
and how to best use the hard work of these creatures to
improve the health and sustainability of our farms.
Imagine a farm where most of the required soil nutrients are provided free, where workers manage pests and diseases at no cost, and where weeds no longer require the unrelenting program of expensive spraying. Right now that might sound impractical, but solid scientific research is showing that with proper management of the biological component of our soils, these objectives don’t sound so crazy.
Science has long known and understood the nature of suppressive soils. Suppressive soils resist diseases; with research is showing that we can grow massive biomass crops using only 10-20% of current nitrogen inputs; farmers are discovering a reduction in weed pressures when the underlying causes of the weeds are understood. These findings have a common explanation in soil biology.
It’s not the soil that’s weed suppressive,
Its whats living in the soil.
These benefits are coming from bacteria, fungi and other micro-organisms that are controlling pathogens, fixing free nitrogen from the air, and maintaining nutritionally balanced soils. Proper management of soil biology is central to sustainable agriculture. These skills have to be learned and applied across the full range of agricultural landscapes. This book represents one step on a journey into a new way of thinking about agricultural sustainability. It provides growers with practical help to start thinking about soils as ecosystems. What is a good bug and what is bad? How many is enough, too much or too little? What do these bugs tell me? And how can I adapt my management practices so that I am not working against the billions of organisms in my soil that can work for me?
There is an old saying that the best fertiliser is the farmer’s footprints – i.e. there is nothing as valuable as having a good close look at what is happening at ground level in the paddock. Central to discovering soil biology is development of the ancient art of observation. Although most farmers feel there is not enough time in the day, it is hoped that a focus on soil biology will encourage growers to climb down from the tractor, take out a 10x lens and take a really good look at what is going on down where it matters, in the soil. What changes are happening seasonally? How has a particular activity impacted on bug numbers? What can I do to boost their numbers? What benefits can I observe from looking after the micro herds?
The pressure from declining terms of trade has promoted a quantity mindset with quality in second place. That pressure threatens to push farms beyond their productive capacity with resulting declines in productivity, rises in pest and disease pressure, and a range of off-site environmental impacts such as sediment or nutrient export to waterways. Managing for quality as well as quantity depends on improved understanding of the soil as an ecosystem. Such knowledge will support landholders’ aspirations to farm sustainably and leave the land in as good or better condition than when they took over.
Compost builds a healthy soil with healthy biological function will produce healthy food and healthy livestock. It may not produce greater quantities of food or livestock, but it can produce comparable quantity with greater quality.
Understanding and Managing Soil Biology
Authors: Declan McDonald, Section Leader
Denis Rodgers, Soil Ecosystems Project Officer
Sustainable Land Use, Land Conservation Branch,
Resource Management and Conservation Division
Department of Primary Industries, Parks, Water and Environment